Home » Biology » AP Biology » The Excretory System

Dr. Carleen Eaton

Dr. Carleen Eaton

The Excretory System

Slide Duration:

Table of Contents

Section 1: Chemistry of Life
Elements, Compounds, and Chemical Bonds

56m 18s

Intro
0:00
Elements
0:09
Elements
0:48
Matter
0:55
Naturally Occurring Elements
1:12
Atomic Number and Atomic Mass
2:39
Compounds
3:06
Molecule
3:07
Compounds
3:14
Examples
3:20
Atoms
4:53
Atoms
4:56
Protons, Neutrons, and Electrons
5:29
Isotopes
10:42
Energy Levels of Electrons
13:01
Electron Shells
13:13
Valence Shell
13:22
Example: Electron Shells and Potential Energy
13:28
Covalent Bonds
19:52
Covalent Bonds
19:54
Examples
20:03
Polar and Nonpolar Covalent Bonds
23:54
Polar Bond
24:07
Nonpolar Bonds
24:17
Examples
24:25
Ionic Bonds
29:04
Ionic Bond, Cations, Anions
29:19
Example: NaCl
29:30
Hydrogen Bond
33:18
Hydrogen Bond
33:20
Chemical Reactions
35:36
Example: Reactants, Products and Chemical Reactions
35:45
Molecular Mass and Molar Concentration
38:45
Avogadro's Number and Mol
39:12
Examples: Molecular Mass and Molarity
42:10
Example 1: Proton, Neutrons and Electrons
47:05
Example 2: Reactants and Products
49:35
Example 3: Bonding
52:39
Example 4: Mass
53:59
Properties of Water

50m 23s

Intro
0:00
Molecular Structure of Water
0:21
Molecular Structure of Water
0:27
Properties of Water
4:30
Cohesive
4:55
Transpiration
5:29
Adhesion
6:20
Surface Tension
7:17
Properties of Water, cont.
9:14
Specific Heat
9:25
High Heat Capacity
13:24
High Heat of Evaporation
16:42
Water as a Solvent
21:13
Solution
21:28
Solvent
21:48
Example: Water as a Solvent
22:22
Acids and Bases
25:40
Example
25:41
pH
36:30
pH Scale: Acidic, Neutral, and Basic
36:35
Example 1: Molecular Structure and Properties of Water
41:18
Example 2: Special Properties of Water
42:53
Example 3: pH Scale
44:46
Example 4: Acids and Bases
46:19
Organic Compounds

53m 54s

Intro
0:00
Organic Compounds
0:09
Organic Compounds
0:11
Inorganic Compounds
0:15
Examples: Organic Compounds
1:15
Isomers
5:52
Isomers
5:55
Structural Isomers
6:23
Geometric Isomers
8:14
Enantiomers
9:55
Functional Groups
12:46
Examples: Functional Groups
12:59
Amino Group
13:51
Carboxyl Group
14:38
Hydroxyl Group
15:22
Methyl Group
16:14
Carbonyl Group
16:30
Phosphate Group
17:51
Carbohydrates
18:26
Carbohydrates
19:07
Example: Monosaccharides
21:12
Carbohydrates, cont.
24:11
Disaccharides, Polysaccharides and Examples
24:21
Lipids
35:52
Examples of Lipids
36:04
Saturated and Unsaturated
38:57
Phospholipids
43:26
Phospholipids
43:29
Example
43:34
Steroids
46:24
Cholesterol
46:28
Example 1: Isomers
48:11
Example 2: Functional Groups
50:45
Example 3: Galactose, Ketose, and Aldehyde Sugar
52:24
Example 4: Class of Molecules
53:06
Nucleic Acids and Proteins

37m 23s

Intro
0:00
Nucleic Acids
0:09
Deoxyribonucleic Acid (DNA) and Ribonucleic Acid (RNA)
0:29
Nucleic Acids, cont.
2:56
Purines
3:10
Pyrimidines
3:32
Double Helix
4:59
Double Helix and Example
5:01
Proteins
12:33
Amino Acids and Polypeptides
12:39
Examples: Amino Acid
13:25
Polypeptide Formation
18:09
Peptide Bonds
18:14
Primary Structure
18:35
Protein Structure
23:19
Secondary Structure
23:22
Alpha Helices and Beta Pleated Sheets
23:34
Protein Structure
25:43
Tertiary Structure
25:44
5 Types of Interaction
26:56
Example 1: Complementary DNA Strand
31:45
Example 2: Differences Between DNA and RNA
33:19
Example 3: Amino Acids
34:32
Example 4: Tertiary Structure of Protein
35:46
Section 2: Cell Structure and Function
Cell Types (Prokaryotic and Eukaryotic)

45m 50s

Intro
0:00
Cell Theory and Cell Types
0:12
Cell Theory
0:13
Prokaryotic and Eukaryotic Cells
0:36
Endosymbiotic Theory
1:13
Study of Cells
4:07
Tools and Techniques
4:08
Light Microscopes
5:08
Light vs. Electron Microscopes: Magnification
5:18
Light vs. Electron Microscopes: Resolution
6:26
Light vs. Electron Microscopes: Specimens
7:53
Electron Microscopes: Transmission and Scanning
8:28
Cell Fractionation
10:01
Cell Fractionation Step 1: Homogenization
10:33
Cell Fractionation Step 2: Spin
11:24
Cell Fractionation Step 3: Differential Centrifugation
11:53
Comparison of Prokaryotic and Eukaryotic Cells
14:12
Prokaryotic vs. Eukaryotic Cells: Domains
14:43
Prokaryotic vs. Eukaryotic Cells: Plasma Membrane
15:40
Prokaryotic vs. Eukaryotic Cells: Cell Walls
16:15
Prokaryotic vs. Eukaryotic Cells: Genetic Materials
16:38
Prokaryotic vs. Eukaryotic Cells: Structures
17:28
Prokaryotic vs. Eukaryotic Cells: Unicellular and Multicellular
18:19
Prokaryotic vs. Eukaryotic Cells: Size
18:31
Plasmids
18:52
Prokaryotic vs. Eukaryotic Cells
19:22
Nucleus
19:24
Organelles
19:48
Cytoskeleton
20:02
Cell Wall
20:35
Ribosomes
20:57
Size
21:37
Comparison of Plant and Animal Cells
22:15
Plasma Membrane
22:55
Plant Cells Only: Cell Walls
23:12
Plant Cells Only: Central Vacuole
25:08
Animal Cells Only: Centrioles
26:40
Animal Cells Only: Lysosomes
27:43
Plant vs. Animal Cells
29:16
Overview of Plant and Animal Cells
29:17
Evidence for the Endosymbiotic Theory
30:52
Characteristics of Mitochondria and Chloroplasts
30:54
Example 1: Prokaryotic vs. Eukaryotic Cells
35:44
Example 2: Endosymbiotic Theory and Evidence
38:38
Example 3: Plant and Animal Cells
41:49
Example 4: Cell Fractionation
43:44
Subcellular Structure

59m 38s

Intro
0:00
Prokaryotic Cells
0:09
Shapes of Prokaryotic Cells
0:22
Cell Wall
1:19
Capsule
3:23
Pili/Fimbria
3:54
Flagella
4:35
Nucleoid
6:16
Plasmid
6:37
Ribosomes
7:09
Eukaryotic Cells (Animal Cell Structure)
8:01
Plasma Membrane
8:13
Microvilli
8:48
Nucleus
9:47
Nucleolus
11:06
Ribosomes: Free and Bound
12:26
Rough Endoplasmic Reticulum (RER)
13:43
Eukaryotic Cells (Animal Cell Structure), cont.
14:51
Endoplasmic Reticulum: Smooth and Rough
15:08
Golgi Apparatus
17:55
Vacuole
20:43
Lysosome
22:01
Mitochondria
25:40
Peroxisomes
28:18
Cytoskeleton
30:41
Cytoplasm and Cytosol
30:53
Microtubules: Centrioles, Spindel Fibers, Clagell, Cillia
32:06
Microfilaments
36:39
Intermediate Filaments and Kerotin
38:52
Eukaryotic Cells (Plant Cell Structure)
40:08
Plasma Membrane, Primary Cell Wall, and Secondary Cell Wall
40:30
Middle Lamella
43:21
Central Cauole
44:12
Plastids: Leucoplasts, Chromoplasts, Chrloroplasts
45:35
Chloroplasts
47:06
Example 1: Structures and Functions
48:46
Example 2: Cell Walls
51:19
Example 3: Cytoskeleton
52:53
Example 4: Antibiotics and the Endosymbiosis Theory
56:55
Cell Membranes and Transport

53m 10s

Intro
0:00
Cell Membrane Structure
0:09
Phospholipids Bilayer
0:11
Chemical Structure: Amphipathic and Fatty Acids
0:25
Cell Membrane Proteins
2:44
Fluid Mosaic Model
2:45
Peripheral Proteins and Integral Proteins
3:19
Transmembrane Proteins
4:34
Cholesterol
4:48
Functions of Membrane Proteins
6:39
Transport Across Cell Membranes
9:52
Transport Across Cell Membranes
9:53
Methods of Passive Transport
12:07
Passive and Active Transport
12:08
Simple Diffusion
12:45
Facilitated Diffusion
15:20
Osmosis
17:17
Definition and Example of Osmosis
17:18
Hypertonic, Hypotonic, and Isotonic
21:47
Active Transport
27:57
Active Transport
28:17
Sodium and Potassium Pump
29:45
Cotransport
34:38
2 Types of Active Transport
37:09
Endocytosis and Exocytosis
37:38
Endocytosis and Exocytosis
37:51
Types of Endocytosis: Pinocytosis
40:39
Types of Endocytosis: Phagocytosis
41:02
Receptor Mediated Endocytosis
41:27
Receptor Mediated Endocytosis
41:28
Example 1: Cell Membrane and Permeable Substances
43:59
Example 2: Osmosis
45:20
Example 3: Active Transport, Cotransport, Simple and Facilitated Diffusion
47:36
Example 4: Match Terms with Definition
50:55
Cellular Communication

57m 9s

Intro
0:00
Extracellular Matrix
0:28
The Extracellular Matrix (ECM)
0:29
ECM in Animal Cells
0:55
Fibronectin and Integrins
1:34
Intercellular Communication in Plants
2:48
Intercellular Communication in Plants: Plasmodesmata
2:50
Cell to Cell Communication in Animal Cells
3:39
Cell Junctions
3:42
Desmosomes
3:54
Tight Junctions
5:07
Gap Junctions
7:00
Cell Signaling
8:17
Cell Signaling: Ligand and Signal Transduction Pathway
8:18
Direct Contact
8:48
Over Distances Contact and Hormones
10:09
Stages of Cell Signaling
11:53
Reception Phase
11:54
Transduction Phase
13:49
Response Phase
14:45
Cell Membrane Receptors
15:37
G-Protein Coupled Receptor
15:38
Cell Membrane Receptor, Cont.
21:37
Receptor Tyrosine Kinases (RTKs)
21:38
Autophosphorylation, Monomer, and Dimer
22:57
Cell Membrane Receptor, Cont.
27:01
Ligand-Gated Ion Channels
27:02
Intracellular Receptors
29:43
Intracellular Receptor and Receptor -Ligand Complex
29:44
Signal Transduction
32:57
Signal Transduction Pathways
32:58
Adenylyl Cyclase and cAMP
35:53
Second Messengers
39:18
cGMP, Inositol Trisphosphate, and Diacylglycerol
39:20
Cell Response
45:15
Cell Response
45:16
Apoptosis
46:57
Example 1: Tight Junction and Gap Junction
48:29
Example 2: Three Phases of Cell Signaling
51:48
Example 3: Ligands and Binding of Hormone
54:03
Example 4: Signal Transduction
56:06
Section 3: Cell Division
The Cell Cycle

37m 49s

Intro
0:00
Functions of Cell Division
0:09
Overview of Cell Division: Reproduction, Growth, and Repair
0:11
Important Term: Daughter Cells
2:25
Chromosome Structure
3:36
Chromosome Structure: Sister Chromatids and Centromere
3:37
Chromosome Structure: Chromatin
4:31
Chromosome with One Chromatid or Two Chromatids
5:25
Chromosome Structure: Long and Short Arm
6:49
Mitosis and Meiosis
7:00
Mitosis
7:41
Meiosis
8:40
The Cell Cycle
10:43
Mitotic Phase and Interphase
10:44
Cytokinesis
15:51
Cytokinesis in Animal Cell: Cleavage Furrow
15:52
Cytokinesis in Plant Cell: Cell Plate
17:28
Control of the Cell Cycle
18:28
Cell Cycle Control System and Checkpoints
18:29
Cyclins and Cyclin Dependent Kinases
21:18
Cyclins and Cyclin Dependent Kinases (CDKSs)
21:20
MPF
23:17
Internal Factor Regulating Cell Cycle
24:00
External Factor Regulating Cell Cycle
24:53
Contact Inhibition and Anchorage Dependent
25:53
Cancer and the Cell Cycle
27:42
Cancer Cells
27:46
Example1: Parts of the Chromosome
30:15
Example 2: Cell Cycle
31:50
Example 3: Control of the Cell Cycle
33:32
Example 4: Cancer and the Cell
35:01
Mitosis

35m 1s

Intro
0:00
Review of the Cell Cycle
0:09
Interphase: G1 Phase
0:34
Interphase: S Phase
0:56
Interphase: G2 Phase
1:31
M Phase: Mitosis and Cytokinesis
1:47
Overview of Mitosis
3:08
What is Mitosis?
3:10
Overview of Mitosis
3:17
Diploid and Haploid
5:37
Homologous Chromosomes
6:04
The Spindle Apparatus
11:57
The Spindle Apparatus
12:00
Centrosomes and Centrioles
12:40
Microtubule Organizing Center
13:03
Spindle Fiber of Spindle Microtubules
13:23
Kinetochores
14:06
Asters
15:45
Prophase
16:47
First Phase of Mitosis: Prophase
16:54
Metaphase
20:05
Second Phase of Mitosis: Metaphase
20:10
Anaphase
22:52
Third Phase of Mitosis: Anaphase
22:53
Telophase and Cytokinesis
24:34
Last Phase of Mitosis: Telophase and Cytokinesis
24:35
Summary of Mitosis
27:46
Summary of Mitosis
27:47
Example 1: Spindle Apparatus
28:50
Example 2: Last Phase of Mitosis
30:39
Example 3: Prophase
32:41
Example 4: Identify the Phase
33:52
Meiosis

1h 58s

Intro
0:00
Haploid and Diploid Cells
0:09
Diploid and Somatic Cells
0:29
Haploid and Gametes
1:20
Example: Human Cells and Chromosomes
1:41
Sex Chromosomes
6:00
Comparison of Mitosis and Meiosis
10:42
Mitosis Vs. Meiosis: Cell Division
10:59
Mitosis Vs. Meiosis: Daughter Cells
12:31
Meiosis: Pairing of Homologous Chromosomes
13:40
Mitosis and Meiosis
14:21
Process of Mitosis
14:27
Process of Meiosis
16:12
Synapsis and Crossing Over
19:14
Prophase I: Synapsis and Crossing Over
19:15
Chiasmata
22:33
Meiosis I
25:49
Prophase I: Crossing Over
25:50
Metaphase I: Homologs Line Up
26:00
Anaphase I: Homologs Separate
28:16
Telophase I and Cytokinesis
29:15
Independent Assortment
30:58
Meiosis II
32:17
Propphase II
33:50
Metaphase II
34:06
Anaphase II
34:50
Telophase II
36:09
Cytokinesis
37:00
Summary of Meiosis
38:15
Summary of Meiosis
38:16
Cell Division Mechanism in Plants
41:57
Example 1: Cell Division and Meiosis
46:15
Example 2: Phases of Meiosis
50:22
Example 3: Label the Figure
54:29
Example 4: Four Differences Between Mitosis and Meiosis
56:37
Section 4: Cellular Energetics
Enzymes

51m 3s

Intro
0:00
Law of Thermodynamics
0:08
Thermodynamics
0:09
The First Law of Thermodynamics
0:37
The Second Law of Thermodynamics
1:24
Entropy
1:35
The Gibbs Free Energy Equation
3:07
The Gibbs Free Energy Equation
3:08
ATP
8:23
Adenosine Triphosphate (ATP)
8:24
Cellular Respiration
11:32
Catabolic Pathways
12:28
Anabolic Pathways
12:54
Enzymes
14:31
Enzymes
14:32
Enzymes and Exergonic Reaction
14:40
Enzymes and Endergonic Reaction
16:36
Enzyme Specificity
21:29
Substrate
21:41
Induced Fit
23:04
Factors Affecting Enzyme Activity
25:55
Substrate Concentration
26:07
pH
27:10
Temperature
29:14
Presence of Cofactors
29:57
Regulation of Enzyme Activity
31:12
Competitive Inhibitors
32:13
Noncompetitive Inhibitors
33:52
Feedback Inhibition
35:22
Allosteric Interactions
36:56
Allosteric Regulators
37:00
Example 1: Is the Inhibitor Competitive or Noncompetitive?
40:49
Example 2: Thermophiles
44:18
Example 3: Exergonic or Endergonic
46:09
Example 4: Energy Vs. Reaction Progress Graph
48:47
Glycolysis and Anaerobic Respiration

38m 1s

Intro
0:00
Cellular Respiration Overview
0:13
Cellular Respiration
0:14
Anaerobic Respiration vs. Aerobic Respiration
3:50
Glycolysis Overview
4:48
Overview of Glycolysis
4:50
Glycolysis Involves a Redox Reaction
7:02
Redox Reaction
7:04
Glycolysis
15:04
Important Facts About Glycolysis
15:07
Energy Invested Phase
16:12
Splitting of Fructose 1,6-Phosphate and Energy Payoff Phase
17:50
Substrate Level Phophorylation
22:12
Aerobic Versus Anaerobic Respiration
23:57
Aerobic Versus Anaerobic Respiration
23:58
Cellular Respiration Overview
27:15
When Cellular Respiration is Anaerobic
27:17
Glycolysis
28:26
Alcohol Fermentation
28:45
Lactic Acid Fermentation
29:58
Example 1: Glycolysis
31:04
Example 2: Glycolysis, Fermentation and Anaerobic Respiration
33:44
Example 3: Aerobic Respiration Vs. Anaerobic Respiration
35:25
Example 4: Exergonic Reaction and Endergonic Reaction
36:42
Aerobic Respiration

51m 6s

Intro
0:00
Aerobic Vs. Anaerobic Respiration
0:06
Aerobic and Anaerobic Comparison
0:07
Review of Glycolysis
1:48
Overview of Glycolysis
2:06
Glycolysis: Energy Investment Phase
2:25
Glycolysis: Energy Payoff Phase
2:58
Conversion of Pyruvate to Acetyl CoA
4:55
Conversion of Pyruvate to Acetyl CoA
4:56
Energy Formation
8:06
Mitochondrial Structure
8:58
Endosymbiosis Theory
9:23
Matrix
10:00
Outer Membrane, Inner Membrane, and Intermembrane Space
10:43
Cristae
11:47
The Citric Acid Cycle
12:11
The Citric Acid Cycle (Also Called Krebs Cycle)
12:12
Substrate Level Phosphorylation
18:47
Summary of ATP, NADH, and FADH2 Production
23:13
Process: Glycolysis
23:28
Process: Acetyl CoA Production
23:36
Process: Citric Acid Cycle
23:52
The Electron Transport Chain
24:24
Oxidative Phosphorylation
24:28
The Electron Transport Chain and ATP Synthase
25:20
Carrier Molecules: Cytochromes
27:18
Carrier Molecules: Flavin Mononucleotide (FMN)
28:05
Chemiosmosis
32:46
The Process of Chemiosmosis
32:47
Summary of ATP Produced by Aerobic Respiration
38:24
ATP Produced by Aerobic Respiration
38:27
Example 1: Aerobic Respiration
43:38
Example 2: Label the Location for Each Process and Structure
45:08
Example 3: The Electron Transport Chain
47:06
Example 4: Mitochondrial Inner Membrane
48:38
Photosynthesis

1h 2m 52s

Intro
0:00
Photosynthesis
0:09
Introduction to Photosynthesis
0:10
Autotrophs and Heterotrophs
0:25
Overview of Photosynthesis Reaction
1:05
Leaf Anatomy and Chloroplast Structure
2:54
Chloroplast
2:55
Cuticle
3:16
Upper Epidermis
3:27
Mesophyll
3:40
Stomates
4:00
Guard Cells
4:45
Transpiration
5:01
Vascular Bundle
5:20
Stroma and Double Membrane
6:20
Grana
7:17
Thylakoids
7:30
Dark Reaction and Light Reaction
7:46
Light Reactions
8:43
Light Reactions
8:47
Pigments: Chlorophyll a, Chlorophyll b, and Carotenoids
9:19
Wave and Particle
12:10
Photon
12:34
Photosystems
13:24
Photosystems
13:28
Reaction-Center Complex and Light Harvesting Complexes
14:01
Noncyclic Photophosphorylation
17:46
Noncyclic Photophosphorylation Overview
17:47
What is Photophosphorylation?
18:25
Noncyclic Photophosphorylation Process
19:07
Photolysis and The Rest of Noncyclic Photophosphorylation
21:33
Cyclic Photophosphorylation
31:45
Cyclic Photophosphorylation
31:46
Light Independent Reactions
34:34
The Calvin Cycle
34:35
C3 Plants and Photorespiration
40:31
C3 Plants and Photorespiration
40:32
C4 Plants
45:32
C4 Plants: Structures and Functions
45:33
CAM Plants
50:25
CAM Plants: Structures and Functions
50:35
Example 1: Calvin Cycle
54:34
Example 2: C4 Plant
55:48
Example 3: Photosynthesis and Photorespiration
58:35
Example 4: CAM Plants
1:00:41
Section 5: Molecular Genetics
DNA Synthesis

38m 45s

Intro
0:00
Review of DNA Structure
0:09
DNA Molecules
0:10
Nitrogenous Base: Pyrimidines and Purines
1:25
DNA Double Helix
3:03
Complementary Strands of DNA
3:12
5' to 3' & Antiparallel
4:55
Overview of DNA Replication
7:10
DNA Replication & Semiconservative
7:11
DNA Replication
10:26
Origin of Replication
10:28
Helicase
11:10
Single-Strand Binding Protein
12:05
Topoisomerases
13:14
DNA Polymerase
14:26
Primase
15:55
Leading and Lagging Strands
16:51
Leading Strand and Lagging Strand
16:52
Okazaki Fragments
18:10
DNA Polymerase I
20:11
Ligase
21:12
Proofreading and Mismatch Repair
22:18
Proofreading
22:19
Mismatch
23:33
Telomeres
24:58
Telomeres
24:59
Example 1: Function of Enzymes During DNA Synthesis
28:09
Example 2: Accuracy of the DNA Sequence
31:42
Example 3: Leading Strand and Lagging Strand
32:38
Example 4: Telomeres
35:40
Transcription and Translation

1h 17m 1s

Intro
0:00
Transcription and Translation Overview
0:07
From DNA to RNA to Protein
0:09
Structure and Types of RNA
3:14
Structure and Types of RNA
3:33
mRNA
6:19
rRNA
7:02
tRNA
7:28
Transcription
7:54
Initiation Phase
8:11
Elongation Phase
12:12
Termination Phase
14:51
RNA Processing
16:11
Types of RNA Processing
16:12
Exons and Introns
16:35
Splicing & Spliceosomes
18:27
Addition of a 5' Cap and a Poly A tail
20:41
Alternative Splicing
21:43
Translation
23:41
Nucleotide Triplets or Codons
23:42
Start Codon
25:24
Stop Codons
25:38
Coding of Amino Acids and Wobble Position
25:57
Translation Cont.
28:29
Transfer RNA (tRNA): Structures and Functions
28:30
Ribosomes
35:15
Peptidyl, Aminoacyl, and Exit Site
35:23
Steps of Translation
36:58
Initiation Phase
37:12
Elongation Phase
43:12
Termination Phase
45:28
Mutations
49:43
Types of Mutations
49:44
Substitutions: Silent
51:11
Substitutions: Missense
55:27
Substitutions: Nonsense
59:37
Insertions and Deletions
1:01:10
Example 1: Three Types of Processing that are Performed on pre-mRNA
1:06:53
Example 2: The Process of Translation
1:09:10
Example 3: Transcription
1:12:04
Example 4: Three Types of Substitution Mutations
1:14:09
Viral Structure and Genetics

43m 12s

Intro
0:00
Structure of Viruses
0:09
Structure of Viruses: Capsid and Envelope
0:10
Bacteriophage
1:48
Other Viruses
2:28
Overview of Viral Reproduction
3:15
Host Range
3:48
Step 1: Bind to Host Cell
4:39
Step 2: Viral Nuclei Acids Enter the Cell
5:15
Step 3: Viral Nucleic Acids & Proteins are Synthesized
5:54
Step 4: Virus Assembles
6:34
Step 5: Virus Exits the Cell
6:55
The Lytic Cycle
7:37
Steps in the Lytic Cycle
7:38
The Lysogenic Cycle
11:27
Temperate Phage
11:34
Steps in the Lysogenic Cycle
12:09
RNA Viruses
16:57
Types of RNA Viruses
17:15
Positive Sense
18:16
Negative Sense
18:48
Reproductive Cycle of RNA Viruses
19:32
Retroviruses
25:48
Complementary DNA (cDNA) & Reverse Transcriptase
25:49
Life Cycle of a Retrovirus
28:22
Prions
32:42
Prions: Definition and Examples
32:45
Viroids
34:46
Example 1: The Lytic Cycle
35:37
Example 2: Retrovirus
38:03
Example 3: Positive Sense RNA vs. Negative Sense RNA
39:10
Example 4: The Lysogenic Cycle
40:42
Bacterial Genetics and Gene Regulation

49m 45s

Intro
0:00
Bacterial Genomes
0:09
Structure of Bacterial Genomes
0:16
Transformation
1:22
Transformation
1:23
Vector
2:49
Transduction
3:32
Process of Transduction
3:38
Conjugation
8:06
Conjugation & F factor
8:07
Operons
14:02
Definition and Example of Operon
14:52
Structural Genes
16:23
Promoter Region
17:04
Regulatory Protein & Operators
17:53
The lac Operon
20:09
The lac Operon: Inducible System
20:10
The trp Operon
28:02
The trp Operon: Repressible System
28:03
Corepressor
31:37
Anabolic & Catabolic
33:12
Positive Regulation of the lac Operon
34:39
Positive Regulation of the lac Operon
34:40
Example 1: The Process of Transformation
39:07
Example 2: Operon & Terms
43:29
Example 3: Inducible lac Operon and Repressible trp Operon
45:15
Example 4: lac Operon
47:10
Eukaryotic Gene Regulation and Mobile Genetic Elements

54m 26s

Intro
0:00
Mechanism of Gene Regulation
0:11
Differential Gene Expression
0:13
Levels of Regulation
2:24
Chromatin Structure and Modification
4:35
Chromatin Structure
4:36
Levels of Packing
5:50
Euchromatin and Heterochromatin
8:58
Modification of Chromatin Structure
9:58
Epigenetic
12:49
Regulation of Transcription
14:20
Promoter Region, Exon, and Intron
14:26
Enhancers: Control Element
15:31
Enhancer & DNA-Bending Protein
17:25
Coordinate Control
21:23
Silencers
23:01
Post-Transcriptional Regulation
24:05
Post-Transcriptional Regulation
24:07
Alternative Splicing
27:19
Differences in mRNA Stability
28:02
Non-Coding RNA Molecules: micro RNA & siRNA
30:01
Regulation of Translation and Post-Translational Modifications
32:31
Regulation of Translation and Post-Translational Modifications
32:55
Ubiquitin
35:21
Proteosomes
36:04
Transposons
37:50
Mobile Genetic Elements
37:56
Barbara McClintock
38:37
Transposons & Retrotransposons
40:38
Insertion Sequences
43:14
Complex Transposons
43:58
Example 1: Four Mechanisms that Decrease Production of Protein
45:13
Example 2: Enhancers and Gene Expression
49:09
Example 3: Primary Transcript
50:41
Example 4: Retroviruses and Retrotransposons
52:11
Biotechnology

49m 26s

Intro
0:00
Definition of Biotechnology
0:08
Biotechnology
0:09
Genetic Engineering
1:05
Example: Golden Corn
1:57
Recombinant DNA
2:41
Recombinant DNA
2:42
Transformation
3:24
Transduction
4:24
Restriction Enzymes, Restriction Sites, & DNA Ligase
5:32
Gene Cloning
13:48
Plasmids
14:20
Gene Cloning: Step 1
17:35
Gene Cloning: Step 2
17:57
Gene Cloning: Step 3
18:53
Gene Cloning: Step 4
19:46
Gel Electrophoresis
27:25
What is Gel Electrophoresis?
27:26
Gel Electrophoresis: Step 1
28:13
Gel Electrophoresis: Step 2
28:24
Gel Electrophoresis: Step 3 & 4
28:39
Gel Electrophoresis: Step 5
29:55
Southern Blotting
31:25
Polymerase Chain Reaction (PCR)
32:11
Polymerase Chain Reaction (PCR)
32:12
Denaturing Phase
35:40
Annealing Phase
36:07
Elongation/ Extension Phase
37:06
DNA Sequencing and the Human Genome Project
39:19
DNA Sequencing and the Human Genome Project
39:20
Example 1: Gene Cloning
40:40
Example 2: Recombinant DNA
43:04
Example 3: Match Terms With Descriptions
45:43
Example 4: Polymerase Chain Reaction
47:36
Section 6: Heredity
Mendelian Genetics

1h 32m 8s

Intro
0:00
Background
0:40
Gregory Mendel & Mendel's Law
0:41
Blending Hypothesis
1:04
Particulate Inheritance
2:08
Terminology
2:55
Gene
3:05
Locus
3:57
Allele
4:37
Dominant Allele
5:48
Recessive Allele
7:38
Genotype
9:22
Phenotype
10:01
Homozygous
10:44
Heterozygous
11:39
Penetrance
11:57
Expressivity
14:15
Mendel's Experiments
15:31
Mendel's Experiments: Pea Plants
15:32
The Law of Segregation
21:16
Mendel's Conclusions
21:17
The Law of Segregation
22:57
Punnett Squares
28:27
Using Punnet Squares
28:30
The Law of Independent Assortment
32:35
Monohybrid
32:38
Dihybrid
33:29
The Law of Independent Assortment
34:00
The Law of Independent Assortment, cont.
38:13
The Law of Independent Assortment: Punnet Squares
38:29
Meiosis and Mendel's Laws
43:38
Meiosis and Mendel's Laws
43:39
Test Crosses
49:07
Test Crosses Example
49:08
Probability: Multiplication Rule and the Addition Rule
53:39
Probability Overview
53:40
Independent Events & Multiplication Rule
55:40
Mutually Exclusive Events & Addition Rule
1:00:25
Incomplete Dominance, Codominance and Multiple Alleles
1:02:55
Incomplete Dominance
1:02:56
Incomplete Dominance, Codominance and Multiple Alleles
1:07:06
Codominance and Multiple Alleles
1:07:08
Polygenic Inheritance and Pleoitropy
1:10:19
Polygenic Inheritance and Pleoitropy
1:10:26
Epistasis
1:12:51
Example of Epistasis
1:12:52
Example 1: Genetic of Eye Color and Height
1:17:39
Example 2: Blood Type
1:21:57
Example 3: Pea Plants
1:25:09
Example 4: Coat Color
1:28:34
Linked Genes and Non-Mendelian Modes of Inheritance

39m 38s

Intro
0:00
Review of the Law of Independent Assortment
0:14
Review of the Law of Independent Assortment
0:24
Linked Genes
6:06
Linked Genes
6:07
Bateson & Pannett: Pea Plants
8:00
Crossing Over and Recombination
15:17
Crossing Over and Recombination
15:18
Extranuclear Genes
20:50
Extranuclear Genes
20:51
Cytoplasmic Genes
21:31
Genomic Imprinting
23:45
Genomic Imprinting
23:58
Methylation
24:43
Example 1: Recombination Frequencies & Linkage Map
27:07
Example 2: Linked Genes
28:39
Example 3: Match Terms to Correct Descriptions
36:46
Example 4: Leber's Optic Neuropathy
38:40
Sex-Linked Traits and Pedigree Analysis

43m 39s

Intro
0:00
Sex-Linked Traits
0:09
Human Chromosomes, XY, and XX
0:10
Thomas Morgan's Drosophila
1:44
X-Inactivation and Barr Bodies
14:48
X-Inactivation Overview
14:49
Calico Cats Example
17:04
Pedigrees
19:24
Definition and Example of Pedigree
19:25
Autosomal Dominant Inheritance
20:51
Example: Huntington's Disease
20:52
Autosomal Recessive Inheritance
23:04
Example: Cystic Fibrosis, Tay-Sachs Disease, and Phenylketonuria
23:05
X-Linked Recessive Inheritance
27:06
Example: Hemophilia, Duchene Muscular Dystrohpy, and Color Blindess
27:07
Example 1: Colorblind
29:48
Example 2: Pedigree
37:07
Example 3: Inheritance Pattern
39:54
Example 4: X-inactivation
41:17
Section 7: Evolution
Natural Selection

1h 3m 28s

Intro
0:00
Background
0:09
Work of Other Scientists
0:15
Aristotle
0:43
Carl Linnaeus
1:32
George Cuvier
2:47
James Hutton
4:10
Thomas Malthus
5:05
Jean-Baptiste Lamark
5:45
Darwin's Theory of Natural Selection
7:50
Evolution
8:00
Natural Selection
8:43
Charles Darwin & The Galapagos Islands
10:20
Genetic Variation
20:37
Mutations
20:38
Independent Assortment
21:04
Crossing Over
24:40
Random Fertilization
25:26
Natural Selection and the Peppered Moth
26:37
Natural Selection and the Peppered Moth
26:38
Types of Natural Selection
29:52
Directional Selection
29:55
Stabilizing Selection
32:43
Disruptive Selection
34:21
Sexual Selection
36:18
Sexual Dimorphism
37:30
Intersexual Selection
37:57
Intrasexual Selection
39:20
Evidence for Evolution
40:55
Paleontology: Fossil Record
41:30
Biogeography
45:35
Continental Drift
46:06
Pangaea
46:28
Marsupials
47:11
Homologous and Analogous Structure
50:10
Homologous Structure
50:12
Analogous Structure
53:21
Example 1: Genetic Variation & Natural Selection
56:15
Example 2: Types of Natural Selection
58:07
Example 3: Mechanisms By Which Genetic Variation is Maintained Within a Population
1:00:12
Example 4: Difference Between Homologous and Analogous Structures
1:01:28
Population Genetic and Evolution

53m 22s

Intro
0:00
Review of Natural Selection
0:12
Review of Natural Selection
0:13
Genetic Drift and Gene Flow
4:40
Definition of Genetic Drift
4:41
Example of Genetic Drift: Cholera Epidemic
5:15
Genetic Drift: Founder Effect
7:28
Genetic Drift: Bottleneck Effect
10:27
Gene Flow
13:00
Quantifying Genetic Variation
14:32
Average Heterozygosity
15:08
Nucleotide Variation
17:05
Maintaining Genetic Variation
18:12
Heterozygote Advantage
19:45
Example of Heterozygote Advantage: Sickle Cell Anemia
20:21
Diploidy
23:44
Geographic Variation
26:54
Frequency Dependent Selection and Outbreeding
28:15
Neutral Traits
30:55
The Hardy-Weinberg Equilibrium
31:11
The Hardy-Weinberg Equilibrium
31:49
The Hardy-Weinberg Conditions
32:42
The Hardy-Weinberg Equation
34:05
The Hardy-Weinberg Example
36:33
Example 1: Match Terms to Descriptions
42:28
Example 2: The Hardy-Weinberg Equilibrium
44:31
Example 3: The Hardy-Weinberg Equilibrium
49:10
Example 4: Maintaining Genetic Variation
51:30
Speciation and Patterns of Evolution

51m 2s

Intro
0:00
Early Life on Earth
0:08
Early Earth
0:09
1920's Oparin & Haldane
0:58
Abiogenesis
2:15
1950's Miller & Urey
2:45
Ribozymes
5:34
3.5 Billion Years Ago
6:39
2.5 Billion Years Ago
7:14
1.5 Billion Years Ago
7:41
Endosymbiosis
8:00
540 Million Years Ago: Cambrian Explosion
9:57
Gradualism and Punctuated Equilibrium
11:46
Gradualism
11:47
Punctuated Equilibrium
12:45
Adaptive Radiation
15:08
Adaptive Radiation
15:09
Example of Adaptive Radiation: Galapogos Islands
17:11
Convergent Evolution, Divergent Evolution, and Coevolution
18:30
Convergent Evolution
18:39
Divergent Evolution
21:30
Coevolution
23:49
Speciation
26:27
Definition and Example of Species
26:29
Reproductive Isolation: Prezygotive
27:49
Reproductive Isolation: Post zygotic
29:28
Allopatric Speciation
30:21
Allopatric Speciation & Geographic Isolation
30:28
Genetic Drift
31:31
Sympatric Speciation
34:10
Sympatric Speciation
34:11
Polyploidy & Autopolyploidy
35:12
Habitat Isolation
39:17
Temporal Isolation
41:27
Selection Selection
41:40
Example 1: Pattern of Evolution
42:53
Example 2: Sympatric Speciation
45:16
Example 3: Patterns of Evolution
48:08
Example 4: Patterns of Evolution
49:27
Section 8: Diversity of Life
Classification

1h 51s

Intro
0:00
Systems of Classification
0:07
Taxonomy
0:08
Phylogeny
1:04
Phylogenetics Tree
1:44
Cladistics
3:37
Classification of Organisms
5:31
Example of Carl Linnaeus System
5:32
Domains
9:26
Kingdoms: Monera, Protista, Plantae, Fungi, Animalia
9:27
Monera
10:06
Phylogentics Tree: Eurkarya, Bacteria, Archaea
11:58
Domain Eukarya
12:50
Domain Bacteria
15:43
Domain Bacteria
15:46
Pathogens
16:41
Decomposers
18:00
Domain Archaea
19:43
Extremophiles Archaea: Thermophiles and Halophiles
19:44
Methanogens
20:58
Phototrophs, Autotrophs, Chemotrophs and Heterotrophs
24:40
Phototrophs and Chemotrophs
25:02
Autotrophs and Heterotrophs
26:54
Photoautotrophs
28:50
Photoheterotrophs
29:28
Chemoautotrophs
30:06
Chemoheterotrophs
31:37
Domain Eukarya
32:40
Domain Eukarya
32:43
Plant Kingdom
34:28
Protists
35:48
Fungi Kingdom
37:06
Animal Kingdom
38:35
Body Symmetry
39:25
Lack Symetry
39:40
Radial Symmetry: Sea Aneome
40:15
Bilateral Symmetry
41:55
Cephalization
43:29
Germ Layers
44:54
Diploblastic Animals
45:18
Triploblastic Animals
45:25
Ectoderm
45:36
Endoderm
46:07
Mesoderm
46:41
Coelomates
47:14
Coelom
47:15
Acoelomate
48:22
Pseudocoelomate
48:59
Coelomate
49:31
Protosomes
50:46
Deuterosomes
51:20
Example 1: Domains
53:01
Example 2: Match Terms with Descriptions
56:00
Example 3: Kingdom Monera and Domain Archaea
57:50
Example 4: System of Classification
59:37
Bacteria

36m 46s

Intro
0:00
Comparison of Domain Archaea and Domain Bacteria
0:08
Overview of Archaea and Bacteria
0:09
Archaea vs. Bacteria: Nucleus, Organelles, and Organization of Genetic Material
1:45
Archaea vs. Bacteria: Cell Walls
2:20
Archaea vs. Bacteria: Number of Types of RNA Pol
2:29
Archaea vs. Bacteria: Membrane Lipids
2:53
Archaea vs. Bacteria: Introns
3:33
Bacteria: Pathogen
4:03
Bacteria: Decomposers and Fix Nitrogen
5:18
Bacteria: Aerobic, Anaerobic, Strict Anaerobes & Facultative Anaerobes
6:02
Phototrophs, Autotrophs, Heterotrophs and Chemotrophs
7:14
Phototrophs and Chemotrophs
7:50
Autotrophs and Heterotrophs
8:53
Photoautotrophs and Photoheterotrophs
10:15
Chemoautotroph and Chemoheterotrophs
11:07
Structure of Bacteria
12:21
Shapes: Cocci, Bacilli, Vibrio, and Spirochetes
12:26
Structures: Plasma Membrane and Cell Wall
14:23
Structures: Nucleoid Region, Plasmid, and Capsule Basal Apparatus, and Filament
15:30
Structures: Flagella, Basal Apparatus, Hook, and Filament
16:36
Structures: Pili, Fimbrae and Ribosome
18:00
Peptidoglycan: Gram + and Gram -
18:50
Bacterial Genomes and Reproduction
21:14
Bacterial Genomes
21:21
Reproduction of Bacteria
22:13
Transformation
23:26
Vector
24:34
Competent
25:15
Conjugation
25:53
Conjugation: F+ and R Plasmids
25:55
Example 1: Species
29:41
Example 2: Bacteria and Exchange of Genetic Material
32:31
Example 3: Ways in Which Bacteria are Beneficial to Other Organisms
33:48
Example 4: Domain Bacteria vs. Domain Archaea
34:53
Protists

1h 18m 48s

Intro
0:00
Classification of Protists
0:08
Classification of Protists
0:09
'Plant-like' Protists
2:06
'Animal-like' Protists
3:19
'Fungus-like' Protists
3:57
Serial Endosymbiosis Theory
5:15
Endosymbiosis Theory
5:33
Photosynthetic Protists
7:33
Life Cycles with a Diploid Adult
13:35
Life Cycles with a Diploid Adult
13:56
Life Cycles with a Haploid Adult
15:31
Life Cycles with a Haploid Adult
15:32
Alternation of Generations
17:22
Alternation of Generations: Multicellular Haploid & Diploid Phase
17:23
Plant-Like Protists
19:58
Euglenids
20:43
Dino Flagellates
22:57
Diatoms
26:07
Plant-Like Protists
28:44
Golden Algae
28:45
Brown Algeas
30:05
Plant-Like Protists
33:38
Red Algae
33:39
Green Algae
35:36
Green Algae: Chlamydomonus
37:44
Animal-Like Protists
40:04
Animal-Like Protists Overview
40:05
Sporozoans (Apicomplexans)
40:32
Alveolates
41:41
Sporozoans (Apicomplexans): Plasmodium & Malaria
42:59
Animal-Like Protists
48:44
Kinetoplastids
48:50
Example of Kinetoplastids: Trypanosomes & African Sleeping Sickness
49:30
Ciliate
50:42
Conjugation
53:16
Conjugation
53:26
Animal-Like Protists
57:08
Parabasilids
57:31
Diplomonads
59:06
Rhizopods
1:00:13
Forams
1:02:25
Radiolarians
1:03:28
Fungus-Like Protists
1:04:25
Fungus-Like Protists Overview
1:04:26
Slime Molds
1:05:15
Cellular Slime Molds: Feeding Stage
1:09:21
Oomycetes
1:11:15
Example 1: Alternation of Generations and Sexual Life Cycles
1:13:05
Example 2: Match Protists to Their Descriptions
1:14:12
Example 3: Three Structures that Protists Use for Motility
1:16:22
Example 4: Paramecium
1:17:04
Fungi

35m 24s

Intro
0:00
Introduction to Fungi
0:09
Introduction to Fungi
0:10
Mycologist
0:34
Examples of Fungi
0:45
Hyphae, Mycelia, Chitin, and Coencytic Fungi
2:26
Ancestral Protists
5:00
Role of Fungi in the Environment
5:35
Fungi as Decomposers
5:36
Mycorrrhiza
6:19
Lichen
8:52
Life Cycle of Fungi
11:32
Asexual Reproduction
11:33
Sexual Reproduction & Dikaryotic Cell
13:16
Chytridiomycota
18:12
Phylum Chytridiomycota
18:17
Zoospores
18:50
Zygomycota
19:07
Coenocytic & Zygomycota Life Cycle
19:08
Basidiomycota
24:27
Basidiomycota Overview
24:28
Basidiomycota Life Cycle
26:11
Ascomycota
28:00
Ascomycota Overview
28:01
Ascomycota Reproduction
28:50
Example 1: Fungi Fill in the Blank
31:02
Example 2: Name Two Roles Played by Fungi in the Environment
32:09
Example 3: Difference Between Diploid Cell and Dikaryon Cell
33:42
Example 4: Phylum of Fungi, Flagellated Spore, Coencytic
34:36
Invertebrates

1h 3m 3s

Intro
0:00
Porifera (Sponges)
0:33
Chordata
0:56
Porifera (Sponges): Sessile, Layers, Aceolomates, and Filter Feeders
1:24
Amoebocytes Cell
4:47
Choanocytes Cell
5:56
Sexual Reproduction
6:28
Cnidaria
8:05
Cnidaria Overview
8:06
Polyp & Medusa: Gastrovasular Cavity
8:29
Cnidocytes
9:42
Anthozoa
10:40
Cubozoa
11:23
Hydrozoa
11:53
Scyphoza
13:25
Platyhelminthes (Flatworms)
13:58
Flatworms: Tribloblastic, Bilateral Symmetry, and Cephalization
13:59
GI System
15:33
Excretory System
16:07
Nervous System
17:00
Turbellarians
17:36
Trematodes
18:42
Monageneans
21:32
Cestoda
21:55
Rotifera (Rotifers)
23:45
Rotifers: Digestive Tract, Pseudocoelem, and Stuctures
23:46
Reproduction: Parthenogenesis
25:33
Nematoda (Roundworms)
26:44
Nematoda (Roundworms)
26:45
Parasites: Pinworms & Hookworms
27:26
Annelida
28:36
Annelida Overview
28:37
Open Circulatory
29:21
Closed Circulatory
30:18
Nervous System
31:19
Excretory System
31:43
Oligochaete
32:07
Leeches
33:22
Polychaetes
34:42
Mollusca
35:26
Mollusca Features
35:27
Major Part 1: Visceral Mass
36:21
Major Part 2: Head-foot Region
36:49
Major Part 3: Mantle
37:13
Radula
37:49
Circulatory, Reproductive, Excretory, and Nervous System
38:14
Major Classes of Molluscs
39:12
Gastropoda
39:17
Polyplacophora
40:15
Bivales
40:41
Cephalopods
41:42
Arthropoda
43:35
Arthropoda Overview
43:36
Segmented Bodies
44:14
Exoskeleton
44:52
Jointed Appendages
45:28
Hemolyph, Excretory & Respiratory System
45:41
Myriapoda & Centipedes
47:15
Cheliceriforms
48:20
Crustcea
49:31
Herapoda
50:03
Echinodermata
52:59
Echinodermata
53:00
Watrer Vascular System
54:20
Selected Characteristics of Invertebrates
57:11
Selected Characteristics of Invertebrates
57:12
Example 1: Phylum Description
58:43
Example 2: Complex Animals
59:50
Example 3: Match Organisms to the Correct Phylum
1:01:03
Example 4: Phylum Arthropoda
1:02:01
Vertebrates

1h 7s

Intro
0:00
Phylum Chordata
0:06
Chordates Overview
0:07
Notochord and Dorsal Hollow Nerve Chord
1:24
Pharyngeal Clefts, Arches, and Post-anal Tail
3:41
Invertebrate Chordates
6:48
Lancelets
7:13
Tunicates
8:02
Hagfishes: Craniates
8:55
Vertebrate Chordates
10:41
Veterbrates Overview
10:42
Lampreys
11:00
Gnathostomes
12:20
Six Major Classes of Vertebrates
12:53
chondrichthyes
14:23
Chondrichthyes Overview
14:24
Ectothermic and Endothermic
14:42
Sharks: Lateral Line System, Neuromastsn, and Gills
15:27
Oviparous and Viviparous
17:23
Osteichthyes (Bony Fishes)
18:12
Osteichythes (Bony Fishes) Overview
18:13
Operculum
19:05
Swim Bladder
19:53
Ray-Finned Fishes
20:34
Lobe-Finned Fishes
20:58
Tetrapods
22:36
Tetrapods: Definition and Examples
22:37
Amphibians
23:53
Amphibians Overview
23:54
Order Urodela
25:51
Order Apoda
27:03
Order Anura
27:55
Reptiles
30:19
Reptiles Overview
30:20
Amniotes
30:37
Examples of Reptiles
32:46
Reptiles: Ectotherms, Gas Exchange, and Heart
33:40
Orders of Reptiles
34:17
Sphenodontia, Squamata, Testudines, and Crocodilia
34:21
Birds
36:09
Birds and Dinosaurs
36:18
Theropods
38:00
Birds: High Metabolism, Respiratory System, Lungs, and Heart
39:04
Birds: Endothermic, Bones, and Feathers
40:15
Mammals
42:33
Mammals Overview
42:35
Diaphragm and Heart
42:57
Diphydont
43:44
Synapsids
44:41
Monotremes
46:36
Monotremes
46:37
Marsupials
47:12
Marsupials: Definition and Examples
47:16
Convergent Evolution
48:09
Eutherians (Placental Mammals)
49:42
Placenta
49:43
Order Carnivora
50:48
Order Raodentia
51:00
Order Cetaceans
51:14
Primates
51:41
Primates Overview
51:42
Nails and Hands
51:58
Vision
52:51
Social Care for Young
53:28
Brain
53:43
Example 1: Distinguishing Characteristics of Chordates
54:33
Example 2: Match Description to Correct Term
55:56
Example 3: Bird's Anatomy
57:38
Example 4: Vertebrate Animal, Marine Environment, and Ectothermic
59:14
Section 9: Plants
Seedless Plants

34m 31s

Intro
0:00
Origin and Classification of Plants
0:06
Origin and Classification of Plants
0:07
Non-Vascular vs. Vascular Plants
1:29
Seedless Vascular & Seed Plants
2:28
Angiosperms & Gymnosperms
2:50
Alternation of Generations
3:54
Alternation of Generations
3:55
Bryophytes
7:58
Overview of Bryrophytes
7:59
Example: Moss Gametophyte
9:29
Example: Moss Sporophyte
9:50
Moss Life Cycle
10:12
Moss Life Cycle
10:13
Seedless Vascular Plants
13:23
Vascular Structures: Cell Walls, and Lignin
13:24
Homosporous
17:11
Heterosporous
17:48
Adaptations to Life on land
21:10
Adaptation 1: Cell Walls
21:38
Adaptation 2: Vascular Plants
21:59
Adaptation 3 : Xylem & Phloem
22:31
Adaptation 4: Seeds
23:07
Adaptation 5: Pollen
23:35
Adaptation 6: Stomata
24:45
Adaptation 7: Reduced Gametophyte Generation
25:32
Example 1: Bryophytes
26:39
Example 2: Sporangium, Lignin, Gametophyte, and Antheridium
28:34
Example 3: Adaptations to Life on Land
29:47
Example 4: Life Cycle of Plant
32:06
Plant Structure

1h 1m 21s

Intro
0:00
Plant Tissue
0:05
Dermal Tissue
0:15
Vascular Tissue
0:39
Ground Tissue
1:31
Cell Types in Plants
2:14
Parenchyma Cells
2:24
Collenchyma Cells
3:21
Sclerenchyma Cells
3:59
Xylem
5:04
Xylem: Tracheids and Vessel Elements
6:12
Gymnosperms vs. Angiosperms
7:53
Phloem
8:37
Phloem: Structures and Function
8:38
Sieve-Tube Elements
8:45
Companion Cells & Sieve Plates
9:11
Roots
10:08
Taproots & Fibrous
10:09
Aerial Roots & Prop Roots
11:41
Structures and Functions of Root: Dicot & Monocot
13:00
Pericyle
16:57
The Nitrogen Cylce
18:05
The Nitrogen Cycle
18:06
Mycorrhizae
24:20
Mycorrhizae
24:23
Ectomycorrhiza
26:03
Endomycorrhiza
26:25
Stems
26:53
Stems
26:54
Vascular Bundles of Monocots and Dicots
28:18
Leaves
29:48
Blade & Petiole
30:13
Upper Epidermis, Lower Epidermis & Cuticle
30:39
Ground Tissue, Palisade Mesophyll, Spongy Mesophyll
31:35
Stomata Pores
33:23
Guard Cells
34:15
Vascular Tissues: Vascular Bundles and Bundle Sheath
34:46
Stomata
36:12
Stomata & Gas Exchange
36:16
Guard Cells, Flaccid, and Turgid
36:43
Water Potential
38:03
Factors for Opening Stoma
40:35
Factors Causing Stoma to Close
42:44
Overview of Plant Growth
44:23
Overview of Plant Growth
44:24
Primary Plant Growth
46:19
Apical Meristems
46:25
Root Growth: Zone of Cell Division
46:44
Root Growth: Zone of Cell Elongation
47:35
Root Growth: Zone of Cell Differentiation
47:55
Stem Growth: Leaf Primodia
48:16
Secondary Plant Growth
48:48
Secondary Plant Growth Overview
48:59
Vascular Cambium: Secondary Xylem and Phloem
49:38
Cork Cambium: Periderm and Lenticels
51:10
Example 1: Leaf Structures
53:30
Example 2: List Three Types of Plant Tissue and their Major Functions
55:13
Example 3: What are Two Factors that Stimulate the Opening or Closing of Stomata?
56:58
Example 4: Plant Growth
59:18
Gymnosperms and Angiosperms

1h 1m 51s

Intro
0:00
Seed Plants
0:22
Sporopollenin
0:58
Heterosporous: Megasporangia
2:49
Heterosporous: Microsporangia
3:19
Gymnosperms
5:20
Gymnosperms
5:21
Gymnosperm Life Cycle
7:30
Gymnosperm Life Cycle
7:31
Flower Structure
15:15
Petal & Pollination
15:48
Sepal
16:52
Stamen: Anther, Filament
17:05
Pistill: Stigma, Style, Ovule, Ovary
17:55
Complete Flowers
20:14
Angiosperm Gametophyte Formation
20:47
Male Gametophyte: Microsporocytes, Microsporangia & Meiosis
20:57
Female Gametophyte: Megasporocytes & Meiosis
24:22
Double Fertilization
25:43
Double Fertilization: Pollen Tube and Endosperm
25:44
Angiosperm Life Cycle
29:43
Angiosperm Life Cycle
29:48
Seed Structure and Development
33:37
Seed Structure and Development
33:38
Pollen Dispersal
37:53
Abiotic
38:28
Biotic
39:30
Prevention of Self-Pollination
40:48
Mechanism 1
41:08
Mechanism 2: Dioecious
41:37
Mechanism 3
42:32
Self-Incompatibility
43:08
Gametophytic Self-Incompatibility
44:38
Sporophytic Self-Incompatibility
46:50
Asexual Reproduction
48:33
Asexual Reproduction & Vegetative Propagation
48:34
Graftiry
50:19
Monocots and Dicots
51:34
Monocots vs.Dicots
51:35
Example 1: Double Fertilization
54:43
Example 2: Mechanisms of Self-Fertilization
56:02
Example 3: Monocots vs. Dicots
58:11
Example 4: Flower Structures
1:00:11
Transport of Nutrients and Water in Plants

40m 30s

Intro
0:00
Review of Plant Cell Structure
0:14
Cell Wall, Plasma Membrane, Middle lamella, and Cytoplasm
0:15
Plasmodesmata, Chloroplasts, and Central Vacuole
3:24
Water Absorption by Plants
4:28
Root Hairs and Mycorrhizae
4:30
Osmosis and Water Potential
5:41
Apoplast and Symplast Pathways
10:01
Apoplast and Symplast Pathways
10:02
Xylem Structure
21:02
Tracheids and Vessel Elements
21:03
Bulk Flow
23:00
Transpiration
23:26
Cohesion
25:10
Adhesion
26:10
Phloem Structure
27:25
Pholem
27:26
Sieve-Tube Elements
27:48
Companion Cells
28:17
Translocation
28:42
Sugar Source and Sugar Sink Overview
28:43
Example of Sugar Sink
30:01
Example of Sugar Source
30:48
Example 1: Match the Following Terms to their Description
33:17
Example 2: Water Potential
34:58
Example 3: Bulk Flow
36:56
Example 4: Sugar Sink and Sugar Source
38:33
Plant Hormones and Tropisms

48m 10s

Intro
0:00
Plant Cell Signaling
0:17
Plant Cell Signaling Overview
0:18
Step 1: Reception
1:03
Step 2: Transduction
2:32
Step 3: Response
2:58
Second Messengers
3:52
Protein Kinases
4:42
Auxins
6:14
Auxins
6:18
Indoleacetic Acid (IAA)
7:23
Cytokinins and Gibberellins
11:10
Cytokinins: Apical Dominance & Delay of Aging
11:16
Gibberellins: 'Bolting'
13:51
Ethylene
15:33
Ethylene
15:34
Positive Feedback
15:46
Leaf Abscission
18:05
Mechanical Stress: Triple Response
19:36
Abscisic Acid
21:10
Abscisic Acid
21:15
Tropisms
23:11
Positive Tropism
23:50
Negative Tropism
24:07
Statoliths
26:21
Phytochromes and Photoperiodism
27:48
Phytochromes: PR and PFR
27:56
Circadian Rhythms
32:06
Photoperiod
33:13
Photoperiodism
33:38
Gerner & Allard
34:35
Short-Day Plant
35:22
Long-Day Plant
37:00
Example 1: Plant Hormones
41:28
Example 2: Cytokinins & Gibberellins
43:00
Example 3: Match the Following Terms to their Description
44:46
Example 4: Hormones & Cell Response
46:14
Section 10: Animal Structure and Physiology
The Respiratory System

48m 14s

Intro
0:00
Gas Exchange in Animals
0:17
Respiration
0:19
Ventilation
1:09
Characteristics of Respiratory Surfaces
1:53
Gas Exchange in Aquatic Animals
3:05
Simple Aquatic Animals
3:06
Gills & Gas Exchange in Complex Aquatic Animals
3:49
Countercurrent Exchange
6:12
Gas Exchange in Terrestrial Animals
13:46
Earthworms
14:07
Internal Respiratory
15:35
Insects
16:55
Circulatory Fluid
19:06
The Human Respiratory System
21:21
Nasal Cavity, Pharynx, Larynx, and Epiglottis
21:50
Bronchus, Bronchiole, Trachea, and Alveoli
23:38
Pulmonary Surfactants
28:05
Circulatory System: Hemoglobin
29:13
Ventilation
30:28
Inspiration/Expiration: Diaphragm, Thorax, and Abdomen
30:33
Breathing Control Center: Regulation of pH
34:34
Example 1: Tracheal System in Insects
39:08
Example 2: Countercurrent Exchange
42:09
Example 3: Respiratory System
44:10
Example 4: Diaphragm, Ventilation, pH, and Regulation of Breathing
45:31
The Circulatory System

1h 20m 21s

Intro
0:00
Types of Circulatory Systems
0:07
Circulatory System Overview
0:08
Open Circulatory System
3:19
Closed Circulatory System
5:58
Blood Vessels
7:51
Arteries
8:16
Veins
10:01
Capillaries
12:35
Vasoconstriction and Vasodilation
13:10
Vasoconstriction
13:11
Vasodilation
13:47
Thermoregulation
14:32
Blood
15:53
Plasma
15:54
Cellular Component: Red Blood Cells
17:41
Cellular Component: White Blood Cells
20:18
Platelets
21:14
Blood Types
21:35
Clotting
27:04
Blood, Fibrin, and Clotting
27:05
Hemophilia
30:26
The Heart
31:09
Structures and Functions of the Heart
31:19
Pulmonary and Systemic Circulation
40:20
Double Circuit: Pulmonary Circuit and Systemic Circuit
40:21
The Cardiac Cycle
42:35
The Cardiac Cycle
42:36
Autonomic Nervous System
50:00
Hemoglobin
51:25
Hemoglobin & Hemocyanin
51:26
Oxygen-Hemoglobin Dissociation Curve
55:30
Oxygen-Hemoglobin Dissociation Curve
55:44
Transport of Carbon Dioxide
1:06:31
Transport of Carbon Dioxide
1:06:37
Example 1: Pathway of Blood
1:12:48
Example 2: Oxygenated Blood, Pacemaker, and Clotting
1:15:24
Example 3: Vasodilation and Vasoconstriction
1:16:19
Example 4: Oxygen-Hemoglobin Dissociation Curve
1:18:13
The Digestive System

56m 11s

Intro
0:00
Introduction to Digestion
0:07
Digestive Process
0:08
Intracellular Digestion
0:45
Extracellular Digestion
1:44
Types of Digestive Tracts
2:08
Gastrovascular Cavity
2:09
Complete Gastrointestinal Tract (Alimentary Canal)
3:54
'Crop'
4:43
The Human Digestive System
5:41
Structures of the Human Digestive System
5:47
The Oral Cavity and Esophagus
7:47
Mechanical & Chemical Digestion
7:48
Salivary Glands
8:55
Pharynx and Epigloltis
9:43
Peristalsis
11:35
The Stomach
12:57
Lower Esophageal Sphincter
13:00
Gastric Gland, Parietal Cells, and Pepsin
14:32
Mucus Cell
15:48
Chyme & Pyloric Sphincter
17:32
The Pancreas
18:31
Endocrine and Exocrine
19:03
Amylase
20:05
Proteases
20:51
Lipases
22:20
The Liver
23:08
The Liver & Production of Bile
23:09
The Small Intestine
24:37
The Small Intestine
24:38
Duodenum
27:44
Intestinal Enzymes
28:41
Digestive Enzyme
33:30
Site of Production: Mouth
33:43
Site of Production: Stomach
34:03
Site of Production: Pancreas
34:16
Site of Production: Small Intestine
36:18
Absorption of Nutrients
37:51
Absorption of Nutrients: Jejunum and Ileum
37:52
The Large Intestine
44:52
The Large Intestine: Colon, Cecum, and Rectum
44:53
Regulation of Digestion by Hormones
46:55
Gastrin
47:21
Secretin
47:50
Cholecystokinin (CCK)
48:00
Example 1: Intestinal Cell, Bile, and Digestion of Fats
48:29
Example 2: Matching
51:06
Example 3: Digestion and Absorption of Starch
52:18
Example 4: Large Intestine and Gastric Fluids
54:52
The Excretory System

1h 12m 14s

Intro
0:00
Nitrogenous Wastes
0:08
Nitrogenous Wastes Overview
0:09
NH3
0:39
Urea
2:43
Uric Acid
3:31
Osmoregulation
4:56
Osmoregulation
5:05
Saltwater Fish vs. Freshwater Fish
8:58
Types of Excretory Systems
13:42
Protonephridia
13:50
Metanephridia
16:15
Malpighian Tubule
19:05
The Human Excretory System
20:45
Kidney, Ureter, bladder, Urethra, Medula, and Cortex
20:53
Filtration, Reabsorption and Secretion
22:53
Filtration
22:54
Reabsorption
24:16
Secretion
25:20
The Nephron
26:23
The Nephron
26:24
The Nephron, cont.
41:45
Descending Loop of Henle
41:46
Ascending Loop of Henle
45:45
Antidiuretic Hormone
54:30
Antidiuretic Hormone (ADH)
54:31
Aldosterone
58:58
Aldosterone
58:59
Example 1: Nephron of an Aquatic Mammal
1:04:21
Example 2: Uric Acid & Saltwater Fish
1:06:36
Example 3: Nephron
1:09:14
Example 4: Gastrointestinal Infection
1:10:41
The Endocrine System

51m 12s

Intro
0:00
The Endocrine System Overview
0:07
Thyroid
0:08
Exocrine
1:56
Pancreas
2:44
Paracrine Signaling
4:06
Pheromones
5:15
Mechanisms of Hormone Action
6:06
Reception, Transduction, and Response
7:06
Classes of Hormone
10:05
Negative Feedback: Testosterone Example
12:16
The Pancreas
15:11
The Pancreas & islets of Langerhan
15:12
Insulin
16:02
Glucagon
17:28
The Anterior Pituitary
19:25
Thyroid Stimulating Hormone
20:24
Adrenocorticotropic Hormone
21:16
Follide Stimulating Hormone
22:04
Luteinizing Hormone
22:45
Growth Hormone
23:45
Prolactin
24:24
Melanocyte Stimulating Hormone
24:55
The Hypothalamus and Posterior Pituitary
25:45
Hypothalamus, Oxytocin, Antidiuretic Hormone (ADH), and Posterior Pituitary
25:46
The Adrenal Glands
31:20
Adrenal Cortex
31:56
Adrenal Medulla
34:29
The Thyroid
35:54
Thyroxine
36:09
Calcitonin
40:27
The Parathyroids
41:44
Parathyroids Hormone (PTH)
41:45
The Ovaries and Testes
43:32
Estrogen, Progesterone, and Testosterone
43:33
Example 1: Match the Following Hormones with their Descriptions
45:38
Example 2: Pancreas, Endocrine Organ & Exocrine Organ
47:06
Example 3: Insulin and Glucagon
48:28
Example 4: Increased Level of Cortisol in Blood
50:25
The Nervous System

1h 10m 38s

Intro
0:00
Types of Nervous Systems
0:28
Nerve Net
0:37
Flatworm
1:07
Cephalization
1:52
Arthropods
2:44
Echinoderms
3:11
Nervous System Organization
3:40
Nervous System Organization Overview
3:41
Automatic Nervous System: Sympathetic & Parasympathetic
4:42
Neuron Structure
6:57
Cell Body & Dendrites
7:16
Axon & Axon Hillock
8:20
Synaptic Terminals, Mylenin, and Nodes of Ranvier
9:01
Pre-synaptic and Post-synaptic Cells
10:16
Pre-synaptic Cells
10:17
Post-synaptic Cells
11:05
Types of Neurons
11:50
Sensory Neurons
11:54
Motor Neurons
13:12
Interneurons
14:24
Resting Potential
15:14
Membrane Potential
15:25
Resting Potential: Chemical Gradient
16:06
Resting Potential: Electrical Gradient
19:18
Gated Ion Channels
24:40
Voltage-Gated & Ligand-Gated Ion Channels
24:48
Action Potential
30:09
Action Potential Overview
30:10
Step 1
32:07
Step 2
32:17
Step 3
33:12
Step 4
35:14
Step 5
36:39
Action Potential Transmission
39:04
Action Potential Transmission
39:05
Speed of Conduction
41:19
Saltatory Conduction
42:58
The Synapse
44:17
The Synapse: Presynaptic & Postsynaptic Cell
44:31
Examples of Neurotransmitters
50:05
Brain Structure
51:57
Meniges
52:19
Cerebrum
52:56
Corpus Callosum
53:13
Gray & White Matter
53:38
Cerebral Lobes
55:35
Cerebellum
56:00
Brainstem
56:30
Medulla
56:51
Pons
57:22
Midbrain
57:55
Thalamus
58:25
Hypothalamus
58:58
Ventricles
59:51
The Spinal Cord
1:00:29
Sensory Stimuli
1:00:30
Reflex Arc
1:01:41
Example 1: Automatic Nervous System
1:04:38
Example 2: Synaptic Terminal and the Release of Neurotransmitters
1:06:22
Example 3: Volted-Gated Ion Channels
1:08:00
Example 4: Neuron Structure
1:09:26
Musculoskeletal System

39m 29s

Intro
0:00
Skeletal System Types and Function
0:30
Skeletal System
0:31
Exoskeleton
1:34
Endoskeleton
2:32
Skeletal System Components
2:55
Bone
3:06
Cartilage
5:04
Tendons
6:18
Ligaments
6:34
Skeletal Muscle
6:52
Skeletal Muscle
7:24
Sarcomere
9:50
The Sliding Filament Theory
13:12
The Sliding Filament Theory: Muscle Contraction
13:13
The Neuromuscular Junction
17:24
The Neuromuscular Junction: Motor Neuron & Muscle Fiber
17:26
Sarcolemma, Sarcoplasmic
21:54
Tropomyosin & Troponin
23:35
Summation and Tetanus
25:26
Single Twitch, Summation of Two Twitches, and Tetanus
25:27
Smooth Muscle
28:50
Smooth Muscle
28:58
Cardiac Muscle
30:40
Cardiac Muscle
30:42
Summary of Muscle Types
32:07
Summary of Muscle Types
32:08
Example 1: Contraction and Skeletal Muscle
33:15
Example 2: Skeletal Muscle and Smooth Muscle
36:23
Example 3: Muscle Contraction, Bone, and Nonvascularized Connective Tissue
37:31
Example 4: Sarcomere
38:17
The Immune System

1h 24m 28s

Intro
0:00
The Lymphatic System
0:16
The Lymphatic System Overview
0:17
Function 1
1:23
Function 2
2:27
Barrier Defenses
3:41
Nonspecific vs. Specific Immune Defenses
3:42
Barrier Defenses
5:12
Nonspecific Cellular Defenses
7:50
Nonspecific Cellular Defenses Overview
7:53
Phagocytes
9:29
Neutrophils
11:43
Macrophages
12:15
Natural Killer Cells
12:55
Inflammatory Response
14:19
Complement
18:16
Interferons
18:40
Specific Defenses - Acquired Immunity
20:12
T lymphocytes and B lymphocytes
20:13
B Cells
23:35
B Cells & Humoral Immunity
23:41
Clonal Selection
29:50
Clonal Selection
29:51
Primary Immune Response
34:28
Secondary Immune Response
35:31
Cytotoxic T Cells
38:41
Helper T Cells
39:20
Major Histocompatibility Complex Molecules
40:44
Major Histocompatibility Complex Molecules
40:55
Helper T Cells
52:36
Helper T Cells
52:37
Mechanisms of Antibody Action
59:00
Mechanisms of Antibody Action
59:01
Opsonization
1:00:01
Complement System
1:01:57
Classes of Antibodies
1:02:45
IgM
1:03:01
IgA
1:03:17
IgG
1:03:53
IgE
1:04:10
Passive and Active Immunity
1:05:00
Passive Immunity
1:05:01
Active Immunity
1:07:49
Recognition of Self and Non-Self
1:09:32
Recognition of Self and Non-Self
1:09:33
Self-Tolerance & Autoimmune Diseases
1:10:50
Immunodeficiency
1:13:27
Immunodeficiency
1:13:28
Chemotherapy
1:13:56
AID
1:14:27
Example 1: Match the Following Terms with their Descriptions
1:15:26
Example 2: Three Components of Non-specific Immunity
1:17:59
Example 3: Immunodeficient
1:21:19
Example 4: Self-tolerance and Autoimmune Diseases
1:23:07
Section 11: Animal Reproduction and Development
Reproduction

1h 1m 41s

Intro
0:00
Asexual Reproduction
0:17
Fragmentation
0:53
Fission
1:54
Parthenogenesis
2:38
Sexual Reproduction
4:00
Sexual Reproduction
4:01
Hermaphrodite
8:08
The Male Reproduction System
8:54
Seminiferous Tubules & Leydig Cells
8:55
Epididymis
9:48
Seminal Vesicle
11:19
Bulbourethral
12:37
The Female Reproductive System
13:25
Ovaries
13:28
Fallopian
14:50
Endometrium, Uterus, Cilia, and Cervix
15:03
Mammary Glands
16:44
Spermatogenesis
17:08
Spermatogenesis
17:09
Oogenesis
21:01
Oogenesis
21:02
The Menstrual Cycle
27:56
The Menstrual Cycle: Ovarian and Uterine Cycle
27:57
Summary of the Ovarian and Uterine Cycles
42:54
Ovarian
42:55
Uterine
44:51
Oxytocin and Prolactin
46:33
Oxytocin
46:34
Prolactin
47:00
Regulation of the Male Reproductive System
47:28
Hormones: GnRH, LH, FSH, and Testosterone
47:29
Fertilization
50:11
Fertilization
50:12
Structures of Egg
50:28
Acrosomal Reaction
51:36
Cortical Reaction
53:09
Example 1: List Three Differences between Spermatogenesis and oogenesis
55:36
Example 2: Match the Following Terms to their Descriptions
57:34
Example 3: Pregnancy and the Ovarian Cycle
58:44
Example 4: Hormone
1:00:43
Development

50m 5s

Intro
0:00
Cleavage
0:31
Cleavage
0:32
Meroblastic
2:06
Holoblastic Cleavage
3:23
Protostomes
4:34
Deuterostomes
5:13
Totipotent
5:52
Blastula Formation
6:42
Blastula
6:46
Gastrula Formation
8:12
Deuterostomes
11:02
Protostome
11:44
Ectoderm
12:17
Mesoderm
12:55
Endoderm
13:40
Cytoplasmic Determinants
15:19
Cytoplasmic Determinants
15:23
The Bird Embryo
22:52
Cleavage
23:35
Blastoderm
23:55
Primitive Streak
25:38
Migration and Differentiation
27:09
Extraembryonic Membranes
28:33
Extraembryonic Membranes
28:34
Chorion
30:02
Yolk Sac
30:36
Allantois
31:04
The Mammalian Embryo
32:18
Cleavage
32:28
Blastocyst
32:44
Trophoblast
34:37
Following Implantation
35:48
Organogenesis
37:04
Organogenesis, Notochord and Neural Tube
37:05
Induction
40:15
Induction
40:39
Fate Mapping
41:40
Example 1: Processes and Stages of Embryological Development
42:49
Example 2: Transplanted Cells
44:33
Example 3: Germ Layer
46:41
Example 4: Extraembryonic Membranes
47:28
Section 12: Animal Behavior
Animal Behavior

47m 48s

Intro
0:00
Introduction to Animal Behavior
0:05
Introduction to Animal Behavior
0:06
Ethology
1:04
Proximate Cause & Ultimate Cause
1:46
Fixed Action Pattern
3:07
Sign Stimulus
3:40
Releases and Example
3:55
Exploitation and Example
7:23
Learning
8:56
Habituation, Associative Learning, and Imprinting
8:57
Habituation
10:03
Habituation: Definition and Example
10:04
Associative Learning
11:47
Classical
12:19
Operant Conditioning
13:40
Positive & Negative Reinforcement
14:59
Positive & Negative Punishment
16:13
Extinction
17:28
Imprinting
17:47
Imprinting: Definition and Example
17:48
Social Behavior
20:12
Cooperation
20:38
Agonistic
21:37
Dorminance Heirarchies
23:23
Territoriality
24:08
Altruism
24:55
Communication
26:56
Communication
26:57
Mating
32:38
Mating Overview
32:40
Promiscuous
33:13
Monogamous
33:32
Polygamous
33:48
Intrasexual
34:22
Intersexual Selection
35:08
Foraging
36:08
Optimal Foraging Model
36:39
Foraging
37:47
Movement
39:12
Kinesis
39:20
Taxis
40:17
Migration
40:54
Lunar Cycles
42:02
Lunar Cycles
42:08
Example 1: Types of Conditioning
43:19
Example 2: Match the Following Terms to their Descriptions
44:12
Example 3: How is the Optimal Foraging Model Used to Explain Foraging Behavior
45:47
Example 4: Learning
46:54
Section 13: Ecology
Biomes

58m 49s

Intro
0:00
Ecology
0:08
Ecology
0:14
Environment
0:22
Integrates
1:41
Environment Impacts
2:20
Population and Distribution
3:20
Population
3:21
Range
4:50
Potential Range
5:10
Abiotic
5:46
Biotic
6:22
Climate
7:55
Temperature
8:40
Precipitation
10:00
Wind
10:37
Sunlight
10:54
Macroclimates & Microclimates
11:31
Other Abiotic Factors
12:20
Geography
12:28
Water
13:17
Soil and Rocks
13:48
Sunlight
14:42
Sunlight
14:43
Seasons
15:43
June Solstice, December Solstice, March Equinox, and September Equinox
15:44
Tropics
19:00
Seasonability
19:39
Wind and Weather Patterns
20:44
Vertical Circulation
20:51
Surface Wind Patterns
25:18
Local Climate Effects
26:51
Local Climate Effects
26:52
Terrestrial Biomes
30:04
Biome
30:05
Forest
31:02
Tropical Forest
32:00
Tropical Forest
32:01
Temperate Broadleaf Forest
32:55
Temperate Broadleaf Forest
32:56
Coniferous/Taiga Forest
34:10
Coniferous/Taiga Forest
34:11
Desert
36:05
Desert
36:06
Grassland
37:45
Grassland
37:46
Tundra
40:09
Tundra
40:10
Freshwater Biomes
42:25
Freshwater Biomes: Zones
42:27
Eutrophic Lakes
44:24
Oligotrophic Lakes
45:01
Lakes Turnover
46:03
Rivers
46:51
Wetlands
47:40
Estuary
48:11
Marine Biomes
48:45
Marine Biomes: Zones
48:46
Example 1: Diversity of Life
52:18
Example 2: Marine Biome
53:08
Example 3: Season
54:20
Example 4: Biotic vs. Abiotic
55:54
Population

41m 16s

Intro
0:00
Population
0:07
Size 'N'
0:16
Density
0:41
Dispersion
1:01
Measure Population: Count Individuals, Sampling, and Proxymeasure
2:26
Mortality
7:29
Mortality and Survivorship
7:30
Age Structure Diagrams
11:52
Expanding with Rapid Growth, Expanding, and Stable
11:58
Population Growth
15:39
Biotic Potential & Exponential Growth
15:43
Logistic Population Growth
19:07
Carrying Capacity (K)
19:18
Limiting Factors
20:55
Logistic Model and Oscillation
22:55
Logistic Model and Oscillation
22:56
Changes to the Carrying Capacity
24:36
Changes to the Carrying Capacity
24:37
Growth Strategies
26:07
'r-selected' or 'r-strategist'
26:23
'K-selected' or 'K-strategist'
27:47
Human Population
30:15
Human Population and Exponential Growth
30:21
Case Study - Lynx and Hare
31:54
Case Study - Lynx and Hare
31:55
Example 1: Estimating Population Size
34:35
Example 2: Population Growth
36:45
Example 3: Carrying Capacity
38:17
Example 4: Types of Dispersion
40:15
Communities

1h 6m 26s

Intro
0:00
Community
0:07
Ecosystem
0:40
Interspecific Interactions
1:14
Competition
2:45
Competition Overview
2:46
Competitive Exclusion
3:57
Resource Partitioning
4:45
Character Displacement
6:22
Predation
7:46
Predation
7:47
True Predation
8:05
Grazing/ Herbivory
8:39
Predator Adaptation
10:13
Predator Strategies
10:22
Physical Features
11:02
Prey Adaptation
12:14
Prey Adaptation
12:23
Aposematic Coloration
13:35
Batesian Mimicry
14:32
Size
15:42
Parasitism
16:48
Symbiotic Relationship
16:54
Ectoparasites
18:31
Endoparasites
18:53
Hyperparisitism
19:21
Vector
20:08
Parasitoids
20:54
Mutualism
21:23
Resource - Resource mutualism
21:34
Service - Resource Mutualism
23:31
Service - Service Mutualism: Obligate & Facultative
24:23
Commensalism
26:01
Commensalism
26:03
Symbiosis
27:31
Trophic Structure
28:35
Producers & Consumers: Autotrophs & Heterotrophs
28:36
Food Chain
33:26
Producer & Consumers
33:38
Food Web
39:01
Food Web
39:06
Significant Species within Communities
41:42
Dominant Species
41:50
Keystone Species
42:44
Foundation Species
43:41
Community Dynamics and Disturbances
44:31
Disturbances
44:33
Duration
47:01
Areal Coverage
47:22
Frequency
47:48
Intensity
48:04
Intermediate Level of Disturbance
48:20
Ecological Succession
50:29
Primary and Secondary Ecological Succession
50:30
Example 1: Competition Situation & Outcome
57:18
Example 2: Food Chains
1:00:08
Example 3: Ecological Units
1:02:44
Example 4: Disturbances & Returning to the Original Climax Community
1:04:30
Energy and Ecosystems

57m 42s

Intro
0:00
Ecosystem: Biotic & Abiotic Components
0:15
First Law of Thermodynamics & Energy Flow
0:40
Gross Primary Productivity (GPP)
3:52
Net Primary Productivity (NPP)
4:50
Biogeochemical Cycles
7:16
Law of Conservation of Mass & Biogeochemical Cycles
7:17
Water Cycle
10:55
Water Cycle
10:57
Carbon Cycle
17:52
Carbon Cycle
17:53
Nitrogen Cycle
22:40
Nitrogen Cycle
22:41
Phosphorous Cycle
29:34
Phosphorous Cycle
29:35
Climate Change
33:20
Climate Change
33:21
Eutrophication
39:38
Nitrogen
40:34
Phosphorous
41:29
Eutrophication
42:55
Example 1: Energy and Ecosystems
45:28
Example 2: Atmospheric CO2
48:44
Example 3: Nitrogen Cycle
51:22
Example 4: Conversion of a Forest near a Lake to Farmland
53:20
Section 14: Laboratory Review
Laboratory Review

2h 4m 30s

Intro
0:00
Lab 1: Diffusion and Osmosis
0:09
Lab 1: Diffusion and Osmosis
0:10
Lab 1: Water Potential
11:55
Lab 1: Water Potential
11:56
Lab 2: Enzyme Catalysis
18:30
Lab 2: Enzyme Catalysis
18:31
Lab 3: Mitosis and Meiosis
27:40
Lab 3: Mitosis and Meiosis
27:41
Lab 3: Mitosis and Meiosis
31:50
Ascomycota Life Cycle
31:51
Lab 4: Plant Pigments and Photosynthesis
40:36
Lab 4: Plant Pigments and Photosynthesis
40:37
Lab 5: Cell Respiration
49:56
Lab 5: Cell Respiration
49:57
Lab 6: Molecular Biology
55:06
Lab 6: Molecular Biology & Transformation 1st Part
55:07
Lab 6: Molecular Biology
1:01:16
Lab 6: Molecular Biology 2nd Part
1:01:17
Lab 7: Genetics of Organisms
1:07:32
Lab 7: Genetics of Organisms
1:07:33
Lab 7: Chi-square Analysis
1:13:00
Lab 7: Chi-square Analysis
1:13:03
Lab 8: Population Genetics and Evolution
1:20:41
Lab 8: Population Genetics and Evolution
1:20:42
Lab 9: Transpiration
1:24:02
Lab 9: Transpiration
1:24:03
Lab 10: Physiology of the Circulatory System
1:31:05
Lab 10: Physiology of the Circulatory System
1:31:06
Lab 10: Temperature and Metabolism in Ectotherms
1:38:25
Lab 10: Temperature and Metabolism in Ectotherms
1:38:30
Lab 11: Animal Behavior
1:40:52
Lab 11: Animal Behavior
1:40:53
Lab 12: Dissolved Oxygen & Aquatic Primary Productivity
1:45:36
Lab 12: Dissolved Oxygen & Aquatic Primary Productivity
1:45:37
Lab 12: Primary Productivity
1:49:06
Lab 12: Primary Productivity
1:49:07
Example 1: Chi-square Analysis
1:56:31
Example 2: Mitosis
1:59:28
Example 3: Transpiration of Plants
2:00:27
Example 4: Population Genetic
2:01:16
Section 15: The AP Biology Test
Understanding the Basics

13m 2s

Intro
0:00
AP Biology Structure
0:18
Section I
0:31
Section II
1:16
Scoring
2:04
The Four 'Big Ideas'
3:51
Process of Evolution
4:37
Biological Systems Utilize
4:44
Living Systems
4:55
Biological Systems Interact
5:03
Items to Bring to the Test
7:56
Test Taking Tips
9:53
Section 16: Practice Test (Barron's 4th Edition)
AP Biology Practice Exam: Section I, Part A, Multiple Choice Questions 1-31

1h 4m 29s

Intro
0:00
AP Biology Practice Exam
0:14
Multiple Choice 1
0:40
Multiple Choice 2
2:27
Multiple Choice 3
4:30
Multiple Choice 4
6:43
Multiple Choice 5
9:27
Multiple Choice 6
11:32
Multiple Choice 7
12:54
Multiple Choice 8
14:42
Multiple Choice 9
17:06
Multiple Choice 10
18:42
Multiple Choice 11
20:49
Multiple Choice 12
23:23
Multiple Choice 13
26:20
Multiple Choice 14
27:52
Multiple Choice 15
28:44
Multiple Choice 16
33:07
Multiple Choice 17
35:31
Multiple Choice 18
39:43
Multiple Choice 19
40:37
Multiple Choice 20
42:47
Multiple Choice 21
45:58
Multiple Choice 22
49:49
Multiple Choice 23
53:44
Multiple Choice 24
55:12
Multiple Choice 25
55:59
Multiple Choice 26
56:50
Multiple Choice 27
58:08
Multiple Choice 28
59:54
Multiple Choice 29
1:01:36
Multiple Choice 30
1:02:31
Multiple Choice 31
1:03:50
AP Biology Practice Exam: Section I, Part A, Multiple Choice Questions 32-63

50m 44s

Intro
0:00
AP Biology Practice Exam
0:14
Multiple Choice 32
0:27
Multiple Choice 33
4:14
Multiple Choice 34
5:12
Multiple Choice 35
6:51
Multiple Choice 36
10:46
Multiple Choice 37
11:27
Multiple Choice 38
12:17
Multiple Choice 39
13:49
Multiple Choice 40
17:02
Multiple Choice 41
18:27
Multiple Choice 42
19:35
Multiple Choice 43
21:10
Multiple Choice 44
23:35
Multiple Choice 45
25:00
Multiple Choice 46
26:20
Multiple Choice 47
28:40
Multiple Choice 48
30:14
Multiple Choice 49
31:24
Multiple Choice 50
32:45
Multiple Choice 51
33:41
Multiple Choice 52
34:40
Multiple Choice 53
36:12
Multiple Choice 54
38:06
Multiple Choice 55
38:37
Multiple Choice 56
40:00
Multiple Choice 57
41:18
Multiple Choice 58
43:12
Multiple Choice 59
44:25
Multiple Choice 60
45:02
Multiple Choice 61
46:10
Multiple Choice 62
47:54
Multiple Choice 63
49:01
AP Biology Practice Exam: Section I, Part B, Grid In

21m 52s

Intro
0:00
AP Biology Practice Exam
0:17
Grid In Question 1
0:29
Grid In Question 2
3:49
Grid In Question 3
11:04
Grid In Question 4
13:18
Grid In Question 5
17:01
Grid In Question 6
19:30
AP Biology Practice Exam: Section II, Long Free Response Questions

31m 22s

Intro
0:00
AP Biology Practice Exam
0:18
Free Response 1
0:29
Free Response 2
20:47
AP Biology Practice Exam: Section II, Short Free Response Questions

24m 41s

Intro
0:00
AP Biology Practice Exam
0:15
Free Response 3
0:26
Free Response 4
5:21
Free Response 5
8:25
Free Response 6
11:38
Free Response 7
14:48
Free Response 8
22:14
Loading...
This is a quick preview of the lesson. For full access, please Log In or Sign up.
For more information, please see full course syllabus of AP Biology
Bookmark & Share Embed

Share this knowledge with your friends!

Copy & Paste this embed code into your website’s HTML

Please ensure that your website editor is in text mode when you paste the code.
(In Wordpress, the mode button is on the top right corner.)
  ×
  • - Allow users to view the embedded video in full-size.
Since this lesson is not free, only the preview will appear on your website.

  • Discussion

  • Answer Engine

  • Study Guides

  • Download Lecture Slides

  • Table of Contents

  • Transcription

  • Related Books & Services

Lecture Comments (11)

1 answer

Last reply by: Dr Carleen Eaton
Thu Mar 27, 2014 11:55 AM

Post by Zhi Lyu on March 22, 2014

It should be antagonistic rather than antagonstic

2 answers

Last reply by: Pedro Ribeiro
Thu Feb 23, 2012 7:57 PM

Post by Pedro Ribeiro on February 22, 2012

Hi,
I think you got the efferent and afferent arterioles switched. I read online and in my textbook that the afferent arteriole brings blood to the glomerulus. The efferent carries it out.

1 answer

Last reply by: Dr Carleen Eaton
Sun Feb 5, 2012 8:50 PM

Post by Dorine Lantimo on February 3, 2012

As the filtrate goes to the thick part of the ascending loop of Henle Nacl is pumped into the cortex of the interstitium via active transport. Why is it active transport n not passive since the cortex environment has lower salt concentration than the filtrate at this time? In addition I am confuse why in the thin part we have passive transport of Nacl into the interstitium an not active transport since the interstium in the medulla is very concentrated compared to the filtrate?

3 answers

Last reply by: Billy Jay
Sun Apr 17, 2011 9:05 PM

Post by Billy Jay on April 17, 2011

Wait - I thought Osmotic Pressure can only exert itself in one particular direction (the area of higher solute concentration / lower water concentration). You had me a little confused around 7:00 min in. You mention that there's an Osmotic Pressure countering the Osmotic Pressure moving into the less concentrated area ... is this the same thing as Oncotic Pressure?

The Excretory System

  • The excretory system is responsible for the removal of nitrogenous wastes and for osmoregulation.
  • The functional unit of the kidney is the nephron. Filtration takes place in the glomerulus where pressure drives water small molecules across the glomerular membrane
  • Reabsorption of water and substances such as NaCl, amino acids and glucose takes place in in the proximal convoluted tubule. Other substances are secreted into the PCT.
  • Aquaporins in the descending loop of Henle allow for water reabsorption in this segment of the tubule.
  • The ascending loop of Henle is impermeable to water. The ascending loop of Henle maintains the concentration gradient from cortex to medulla by transporting NaCl into the interstitium.
  • In the distal convoluted tubule both reabsorption and secretion take place.
  • The collecting duct is permeable to water when acted upon by antidiuretic hormone (ADH). ADH stimulates the reabsorption of water by the kidney.
  • Aldosterone is released in response to low blood pressure or blood volume and stimulates the reabsorption of Na+ by the distal convoluted tubule.

The Excretory System

Lecture Slides are screen-captured images of important points in the lecture. Students can download and print out these lecture slide images to do practice problems as well as take notes while watching the lecture.

  • Intro 0:00
  • Nitrogenous Wastes 0:08
    • Nitrogenous Wastes Overview
    • NH3
    • Urea
    • Uric Acid
  • Osmoregulation 4:56
    • Osmoregulation
    • Saltwater Fish vs. Freshwater Fish
  • Types of Excretory Systems 13:42
    • Protonephridia
    • Metanephridia
    • Malpighian Tubule
  • The Human Excretory System 20:45
    • Kidney, Ureter, bladder, Urethra, Medula, and Cortex
  • Filtration, Reabsorption and Secretion 22:53
    • Filtration
    • Reabsorption
    • Secretion
  • The Nephron 26:23
    • The Nephron
  • The Nephron, cont. 41:45
    • Descending Loop of Henle
    • Ascending Loop of Henle
  • Antidiuretic Hormone 54:30
    • Antidiuretic Hormone (ADH)
  • Aldosterone 58:58
    • Aldosterone
  • Example 1: Nephron of an Aquatic Mammal 1:04:21
  • Example 2: Uric Acid & Saltwater Fish 1:06:36
  • Example 3: Nephron 1:09:14
  • Example 4: Gastrointestinal Infection 1:10:41

Transcription: The Excretory System

Welcome to Educator.com0000

In this section, we are going to continue our discussion of animal physiology with the focus on the excretory system.0002

The excretory system has two major functions.0010

One is the excretion of waste. The other is a role in homeostasis particularly osmoregulation.0013

Beginning first with its function as an excretory system, nitrogenous waste are produced by the breakdown of nitrogen-containing compounds,0024

for example, proteins and nucleic acids.0035

One product of this breakdown is ammonia, which is NH3. The thing about ammonia is it is very toxic in high concentrations.0040

So, there are some animals that directly excrete ammonia. However, many animals convert ammonia to less toxic substances and then, excrete those.0053

The less toxic substances that I am talking about are urea and uric acid. Those are the two main ones.0065

First, talking about animals that actually directly excrete ammonia, these are animals that live in the water,0070

so, animals that live in the water, that live in an aqueous environment directly0080

excreted by some animals that live in an aqueous environment- aqueous-dwelling animals.0090

This is because if an animal lives in the water, it is constantly exposed to very large amounts of water.0103

So, all this water coming in and bathing the animal dilutes out the ammonia during transport and during the excretion of ammonia.0109

So, the ammonia cannot concentrate and then, damage the animal cells.0119

Fish, for example, excrete ammonia through their gills, and a lot of water is passing through the gills; and it dilutes out the ammonia.0123

Simpler aquatic animals such as a hydra just excrete the ammonia through diffusion directly from their cells, directly into the water.0141

There are, however, some aquatic animals like sharks that do not secrete ammonia directly.0152

Sharks convert their ammonia to urea like many land-dwelling animals do.0158

So, let's now talk about the second common waste product, which is urea.0164

Many animals including mammals as well as annelids like earthworms excrete urea as their nitrogenous waste, and urea is much less toxic than ammonia.0171

Without this constant exposure to water, urea is a safer material to transport and excrete.0187

In mammals, urea is formed in the liver. In the liver, ammonia is converted to urea, which, then, leaves the body via the excretory system.0196

Another option for nitrogenous waste for animals is uric acid.0213

Reptiles and birds secrete or excrete nitrogenous waste in the form of uric acid. This is also less toxic than ammonia.0219

A major difference between urea and uric acid is that uric acid is poorly soluble in water.0231

In fact, uric acid has a consistency that is somewhat like paste.0243

And this is an advantage to animals like reptiles and birds that may have to go without water for a while. They live in drier environments.0247

So, instead of secreting urea in the urine and having to have this solute in a lot of water and lose a lot of water that way,0257

they can secrete uric acid from the body with very little water loss, so uric acid is an advantage for an animal that lives in a drier environment.0265

Now, the conversion of ammonia to either urea or uric acid has a cost, and that cost is energy.0275

This is an energy-requiring process, but it is a necessary one because the toxicity of ammonia would be a problem for animals,0283

especially land animals that do not have all this water diluting out the ammonia.0291

Excretion of nitrogenous waste is one major function of the excretory system, but another one is osmoregulation.0297

In many species, the second major function of the excretory system is a role in homeostasis.0306

Osmoregulation is a maintenance of a constant solute concentration in an organism.0313

So, to understand this, we are just going to go back to some basics of chemistry and talk about solutes and movement of water and osmosis.0319

Let's say I have a compartment separated by a semipermeable membrane meaning that water can cross this membrane but solutes, particles, cannot.0331

On one side, let's say I have a higher concentration of solute. The other side is going to be more dilute, a lower concentration of solutes.0344

This side is the hyperosmolar side. This side is hypoosmolar.0354

Water is going to move from the area of more water, or you could look at it either way.0369

You could look at it as the area of lower solute concentration, the hypoosmolar side to the hyperosmolar side to dilute this out.0379

Or you could look at it as water via osmosis is going down its concentration gradient0387

to an area of greater water concentration to an area of lower water concentration.0392

This is very similar to what we talked about when we talked about cells and we said hypotonic, hypertonic and talked about0399

water entering the cells if they were hypertonic, water leaving the cells if they were hypotonic relative to their environment.0407

So, here I am talking about just two different liquids, but it is the same idea with what we are talking about with a cell in a solution.0413

Osmotic pressure is a term that you should understand, and the solute concentration here is drawing water in.0423

The pressure that would needed to be applied to prevent this water from rushing in, to counteract,0434

there is a certain pull that these particles are essentially pulling water in.0441

Well, the pressure that you would need to counteract that is the osmotic pressure of the solution.0446

So, the osmotic pressure on this side is much lower because there are fewer solutes. You would need much lower pressure.0451

Well, actually, there would not be in that movement to that side.0457

But, the osmotic pressure exerted by these solutes, since they are less concentrated, is lower than the osmotic pressure on this side.0460

When we talk about osmolarity, we are really discussing solute concentration, and the unit of measurement of osmolarity is the osmole.0471

And a lot of times, we will talk about milliosmoles. We might say "oh, a solution is 500 milliosmoles per liter".0481

Therefore, when we talk about osmoregulation, we are talking about the maintenance of a constant solute concentration in the blood.0492

Solutes and fluid are obviously very closely-related, so by regulating osmolarity, the kidney is also helping to regulate fluid volume.0504

In mammals, the kidney has a major role in osmoregulation.0514

Before we get on to talking about mammals though, I want to talk about osmoregulation in some very challenging situations.0520

Animals that live in freshwater or in saltwater both face very challenging situations0526

because they are immersed in either a hyperosmolar or hypoosmolar environment.0532

So, let's talk about fish that are living in saltwater. The ocean water is hyperosmolar, their environment.0539

This fish wants to keep its body fluids at a lower osmolarity than the surrounding ocean.0557

So, it is constantly having to fight against the fact that the water is going to want to diffuse out of the fish.0567

So, you have this fish, and he is swimming around in the ocean; and the ocean has a higher solute concentration than in the fish's body.0575

Water wants to leave the fish, his body, so he is fighting dehydration.0592

If he does not fight against it, water will just leave until there is an iso-osmolarity and the solute concentration inside and outside the fish is the same.0599

In order to compensate for loss of water in a saltwater environment, the fish has some mechanisms.0612

One: they drink a lot. Now, when they are drinking, they are drinking seawater, so they are getting the water; but they are getting salt too.0620

So, he is losing water, so he is compensating by drinking water; but as he drinks water, salt is coming into his body.0630

So, what he does is he keeps the water and gets rid of the salt, and in fact, fish in saltwater environments excrete salts via their gills.0636

And this requires active transport because the salt is being moved against its concentration gradient, so this is an energy-requiring process.0647

In addition, they excrete salts via their kidneys, so the kidneys excrete salts into the urine to leave the body.0656

And they only urinate small amounts, so they get rid of the salt essentially and keep the water, so just urinate small volumes.0670

They do not lose a lot of the water via urine.0680

The opposite challenge is presented to a freshwater fish. This fish is living in a hypoosmolar environment.0687

Here is a fish, and there is not a lot of solutes out here. It is a low osmolarity environment.0700

There is more solutes inside the fish.0709

As a result, water wants to keeps rushing in and diluting out his body fluids and diluting out, then, the salt concentration.0711

What this fish needs to do is maintain his salt concentration, and he needs to get rid of excess water and hold on to salts.0721

So, this fish needs to get rid of salt. This fish needs to get rid of excess water.0729

This is accomplished by one: not drinking water. This fish is not going to drink water all the time like this one.0741

This fish is going to take salts in via his gills. In a saltwater environment, a fish excretes salt through the gills.0753

In a freshwater environment, the fish is going to take up salt through its gills, and this fish is going to urinate large amounts of dilute urine,0765

so getting rid of the water by just urinating out the excess water, holding on to the salt, getting rid of the water.0782

I do want to note that some invertebrates in, for example, saltwater environments, have a different method of adaptation.0791

Instead of fighting against the osmolarity of the saltwater and trying to get rid of all the salt,0798

some certain animals actually have a high osmolarity that is the same as seawater.0806

So, their body fluids are as concentrated as the water around them, and there is not this net loss of water to the external environment.0810

Let's start out with an overview of types of excretory systems before focusing on the human excretory system.0823

Starting out with some simpler animals and talking about a system called protonephridia, now, some flatworms just remove nitrogenous waste via diffusion.0831

The nitrogenous waste just diffuse across body surfaces. There are others, though, some types of flatworms use protonephridia.0847

Rotifers use protonephridia, and what protonephridia are, are a network of small tubes; and these small tubes lead to ducts.0858

And the nitrogenous waste are, then, excreted through the ducts, so the ducts connect to the outside of the body,0875

so, a network a tubes leading to ducts leading to the outside.0885

These ducts, though...so, let's say we have this worm - I will draw it a little bit bigger - and he has got this protonephridia.0888

And it leads to a duct to the outside where waste or nitrogenous waste are excreted.0906

Essentially he is urinating. Let's look at it that way, but it is a much simpler system, and these ducts are blind-ending.0913

So, they are open on this end. On this end, it is blind-ending, and at this thermal end, it is what is called a flame bulb.0922

If you look at the flame bulb, there are cilia that project inside in the lumen of the tubule.0935

And what happens is, then, fluid goes in, and these cilia help to move the fluid along the tubule and then, on out.0946

In this way, nitrogenous waste can leave the body, exit their tubules and then, exit out of the surface of the body via ducts.0959

Earthworms and other annelids have a different system. It is called metanephridia, and recall that earthworms have segments.0974

They also have a true coelom, and each segment in an earthworm has a pair of nephridia, so there is one pair per segment.0986

And what these consist of, what a metanephridia consist of, is a tubule surrounded by a network of capillaries, and there is also a bladder.0995

There are two openings here in this system, so here, we are going to have an earthworm, and there are actually two openings:1014

An external opening, and then, we have a system, and then, we have an internal opening.1026

So, the external opening is called the nephridiopore, and then, the internal opening is called the nephrostome.1033

Body fluid within the worm is going to enter this internal opening, the nephrostome.1054

It is going to pass into this tubule, go through the tubule and be processed and then, reach the bladder.1062

It will be urine, and then, exit the body as urine. As the fluid is going through the tubule, it is being processed.1071

And a lot of what we are going to talk about today, we talked about the human kidney is this processing.1081

By processing, I mean that at first, the fluid that goes in here might have some things that the animal does not want to lose.1086

It might need to retain salt. There might be nutrients in there, so things that we do not want to lose as waste are reabsorbed.1093

In addition, there may be waste products that are not initially in the fluid that is leaving the body.1103

So, those waste products can be secreted into the tubule to leave the body.1110

Just very simply, processing takes place in which certain substances are picked up and retained in the body.1115

Others are secreted to leave the body, and then, the urine with the waste products exits the body.1121

So, the constitution of fluid in an excretory system changes as it goes to the body.1129

Here, it is filtered. Processing takes place, and what starts out is what we call filtrate.1135

It ends up being urine.1143

Malpighian tubules are found in many arthropod excretory systems.1146

And this is a different system because these are tubules that project out from the GI tract.1162

So, if you had some insect, and he has this GI tract here, there are tubules the project out from the GI tract.1169

Food is being processed in the GI tract, and then, waste is leaving, exiting the GI tract.1187

Meanwhile, these Malpighian tubules are absorbing or picking up fluid from the body.1193

The hemolymph, which is the circulatory fluid, would be filtered, and this is processed; and then, it actually enters the GI tract.1203

The urine is going to be eliminated along with feces in this type of system because it dumps out into the GI tract.1213

Most of the water that is initially in this urine is reabsorbed along the way in the GI tract.1223

So, this is a good system for insects that live in dry environments and that need to conserve water because very little water is lost.1229

Most of what is exiting the body through the excretory system is actually nitrogenous waste.1238

We are now going to focus on the human excretory system, and a lot of this will apply to other mammals, as well, but again, this is the human system.1245

Humans have a pair of kidneys that filter the blood, and function in both osmoregulation, as I mentioned, and in the excretion of waste.1254

After the urine is formed in the kidneys, it exits via the ureters. There is a ureter leading from each kidney to the bladder.1267

Urine is stored in the bladder and then, leaves through the urethra.1279

So, this is just the basic structure, and we are going to go into a lot more detail particularly about the kidney.1288

The kidney has two sections. This outer portion here is the cortex, and this portion is the medulla.1295

The functional unit of the kidney is the nephron, so the kidney contains nephrons; and that is where the urine is made.1306

There are about 1 million nephrons per kidney, and a huge volume of blood passes through the kidneys every day.1319

In fact, one quarter of the blood that is leaving the heart goes through the kidneys.1327

Blood supply: the renal artery delivers blood to the kidneys, so we have the renal artery.1333

And then, we have the renal vein. The blood leaves the kidneys through the renal vein.1351

Before we talk about how the kidney works, you need to make sure that you understand certain terminologies.1368

The first term you need to be familiar with is filtration. Filtration is the process of the blood passing through a semipermeable membrane.1375

During filtration, certain substances will enter the kidney, those that can pass through the membrane.1397

Other substances in the blood just stay in the blood vessel and stay in the circulation.1405

Those items that pass through...so here, we have the blood vessel, which I will do in detail later about the nephron and the tubule.1411

And there is filtration right here. Those things that can pass through the capillary membrane enter the renal tubule.1424

And this liquid in solutes in this solution is the filtrate.1433

The filtrate consists of everything that passed through the membrane, that made it through the membrane into the kidney.1439

As the filtrate goes through the nephron, the filtrate enters the nephron, it enters the tubule, it is processed.1446

And processing consists of reabsorption and secretion.1456

So, it is important that you understand the difference between these two. These terms get commonly turned around and mixed up.1468

Reabsorption is the process of returning substances to the blood, so substances go from the nephron, from the tubule to the blood.1475

These are things that the body wants to keep, for example, glucose. The body uses glucose.1494

We do not want it lost in the urine. That would be reabsorbed.1500

In certain cases, some substances can be reabsorbed at certain times, secreted at others.1504

But, just keeping it simple, reabsorption are substances that we are putting back into the body, either temporarily or permanently you want to keep.1510

Secretion, that is the opposite process. Secretion is removing substances from the blood.1522

So, in reabsorption, substances are going to go back into the bloodstream.1540

In secretion, substances are going to go into the tubule to leave the body, so removing substances from the blood.1546

In other words, a substance or something that we want to get rid of. It could be excess hydrogen ions.1555

In a certain part of the kidney, it is urea. A substance goes from the blood into the tubule.1563

So, these are things we are putting into the filtrate or into the urine. Reabsorption is removing things from the filtrate or from the urine.1573

This sketch shows a nephron that has been, sort of, flattened out and stretched out.1585

In the kidney, they are actually a lot more coiled up, but to look at this for clarity, this is flattened out.1590

And remember that the kidney has two parts. It has the outer cortex, and it has an inner medulla.1596

So, if I cut the kidney in half, and I sectioned it, I am looking at this section of an opened-up kidney, and I looked at nephrons,1608

and there is a million of them here, what I would see is that these nephrons have portions.1617

If I relate their order into a certain way so that this portion - actually, I will draw that a little bit lower - all of this here is in the cortex.1624

And then, all these, this part, all these down here is in the medulla.1644

So, if I laid this, if I took this and I laid it out here, I would see this glomerulus up here in the cortex, the first part of the tubule here and then,1651

the loop reaching into the medulla and then, this latter part in the cortex, this long collecting duct going down into the medulla, so this is how it is oriented.1660

I am going to go through just an overview of what the different sections are and then,1674

what happens in each section because there is quite a lot to understand, so we are going to spend a lot of time on the nephron.1680

There are two major structures that comprise a nephron. The first is the glomerulus, and the second is this big, all this whole tubule, this renal tubule.1688

The glomerulus is a cluster of capillaries, so it is a cluster of capillaries; and it is located inside this cups-shaped structure called...1705

So, this is the glomerulus. This is Bowman’s capsule.1716

This is the section where filtration occurs, and I am going to go into that in detail after I just finish naming all the structures.1726

So, after filtration, the filtrate enters Bowman’s capsule and then, the renal tubule.1734

This first part of the renal tubule here is called the proximal convoluted tubule or just the proximal tubule.1743

This entire structure here, this loop, is called the loop of Henle.1759

And it is divided into two regions: the descending loop that goes down, and then, we have this turn; and the ascending loop.1765

So, there is a descending loop of Henle and an ascending loop of Henle, and they each have different structure and different functions.1774

As the filtrate enters the renal tubule, it is being processed. There are things being secreted into it.1782

There are things being reabsorbed. Water is moving around.1788

All this is happening throughout, and then, we get through the loop of Henle and enter the distal convoluted tubule or just the distal tubule.1793

Finally, we get to this terminal part of the nephron, which is the collecting duct.1812

And you will notice this is open at the top, and the reason is that urine from other nephrons can drain into a single collecting duct.1819

Urine from this nephron and then, there could be another nephron that drains into here.1829

When this fluid starts out, it is called filtrate. By the time it gets to the collecting duct, it is urine.1834

And then, the collecting ducts are all going to drain into the renal pelvis.1841

The urine will exit the kidney, go through the ureter, be stored in the bladder and go out the urethra.1846

This is just the big picture, and now, what we are going to do is focus first on the glomerulus and filtration.1854

Blood enters the glomerulus through this afferent arterial. It is called an afferent arterial with an A.1865

And then, the glomerulus is this network of capillaries. Blood exits the glomerulus through the efferent arterial.1882

Well, where is this blood coming from?1895

The blood enters the kidney through the renal artery, branches from the renal artery, branch off into afferent arterials.1899

These branch further into capillaries, then, form the efferent arterial, and the blood leaves the kidney.1908

Filtration is driven by the blood pressure within the glomerular vessels.1917

The fluid within these vessels is creating pressure, and that pressure is pushing this filtrate through.1923

And the blood is filtered across the glomerular membrane.1931

Certain substances can pass through the capillary membrane of the glomerulus.1937

These substances will enter this little space here called Bowman’s space and then, enter Bowman’s capsule and now be in the renal tubule as filtrate.1943

So, here is where the filtrate is created through filtration. What you should know is what substances enter the filtrate, are part of the filtrate.1957

So, what substances are small enough to get through the glomerular membrane and enter the filtrate?1968

Well, a major component of the filtrate is water. Other substances that can enter the filtrate are salts.1975

You will find sodium and chloride in the filtrate. Glucose can also enter the filtrate.1989

Amino acids are small enough to enter the filtrate, so things need to be small to get through this capillary membrane.1996

Vitamins can enter the filtrate, nitrogenous wastes such as urea.2003

Now, what cannot enter? What is too big to be filtered?2013

So, cannot enter the filtrate, cells are an example and proteins, red blood cells, white blood cells, proteins.2022

Amino acids can get in, but cells and proteins cannot; and, of course, there is plenty of fluids still left in the vessel here.2030

If somehow red blood cells and white blood cells are passing through this glomerular membrane, there is a problem with the glomerular membrane.2038

There is some kind of disease process going on, and so, in fact, if somebody has blood cells or protein or things in their urine that can be a clue,2046

there are many possibilities that different levels of the urinary tract system, but one possibility is something is going on with the glomerulus.2056

So, cells and protein should not be in the filtrate. These items are in the filtrate.2064

By the time we get to the urine, things like glucose will no longer be in there. They will have been taken back up by the body.2069

Other things will be secreted and added to the filtrate, so the composition of the filtrate changes a lot as it goes through each step until it becomes urine.2076

Urine is very different than filtrate. Filtrate reflects some of the composition of the plasma, whereas, urine is just very different.2085

Before we talk about what happens to the filtrate now that it is here entering the proximal convoluted tubule,2097

I am going to talk a bit more about the blood supply to the kidney.2105

So, blood components that have not passed into Bowman’s capsule: of course, some of the water, the red blood cells, the white blood cells, the proteins.2110

These components that have not made it into the filtrate continue out and leave the glomerulus via the efferent arterial.2122

In addition, the efferent arterial branches off to form capillaries that surround the proximal convoluted tubule and the distal convoluted tubule.2135

And there needs to be a blood supply around these tubules because items are being2146

picked up to put back into the blood or secreted from the blood into the nephron.2152

The nephron's work involves taking things from the bloodstream and putting things into the bloodstream.2161

So, there needs to be a blood supply closely associated with the renal tubule.2166

There is also a set of vessels called the vasa recta, and these are a group of capillaries, so the vasa recta.2172

These are a group of capillaries that are associated with the loop of Henle.2180

They involve one of these counter current exchange systems that we have talked about earlier on, and it actually allows the kidney to concentrate urine.2187

And I am going to talk about the loop of Henle's role in concentrating urine when we get to that part.2197

So, right now, what we left with was filtrate had been formed. It contains water and these substances, various ions.2203

And it enters the proximal convoluted tubule. The proximal convoluted tubule is a very important site for the reabsorption of products and for secretion.2214

So, I am going to clear out some space here, and we are going to talk about what is reabsorbed, what is secreted, what happens here.2226

Water and certain solutes are reabsorbed, and then, other solutes are secreted; so let's start out with reabsorption.2237

And I am going to use red. This is going to be active reabsorption, and then, I will just use blue for passive reabsorption.2247

The filtrate is here in the tubule.2263

And sodium chloride diffuses from the lumen of the tubule, from the space inside the tubule into these epithelial cells of the nephron that line the tubules.2266

So, filtrate is passing through, and there is sodium; and there is chloride, and there are these cells, and this sodium chloride is taken up by these cells.2278

From there, the epithelial cells actively transport the sodium into the interstitial fluid. Excuse me, interstitial fluid, so out here.2297

Outside of the tubule is the interstitial fluid, which plays an important role in the function of the nephron.2310

And the sodium is going to be actively transported from these cells in the tubule outside to the interstitial fluid. Chloride follows passively.2316

Now, glucose, amino acids and other substances are also actively transported outside to this interstitial fluid.2331

And then, from the interstitial fluid, these items are picked up by blood vessels.2343

So, reabsorption involves taking substances from the tubule, putting them back in the bloodstream, and that occurs via a couple steps.2349

The substances end up in the interstitial fluid, and then, they are picked up by these capillaries that are surrounding the nephron.2357

So, sodium that is actively transported, chloride follows passively.2364

There are a number of other items that are actively transported, so remember that glucose, we do not want glucose to be lost in the urine.2369

That is something our bodies could use, the same with amino acids.2379

So, these things are all reabsorbed: glucose, amino acids, vitamins. We do not want to just urinate out important vitamins.2384

Those are actively transported.2398

Now, where solutes go, water follows. Sodium is particularly important in osmolarity, and in fact, where sodium goes, water usually follows by osmosis.2403

So, as the sodium leaves, and the chloride follows through passive transport, water is also being reabsorbed.2413

In summary for reabsorption, we have sodium and chloride with water following.2426

We have glucose, amino acids and vitamins all being reabsorbed in the proximal convoluted tubule.2431

Now, let's talk about secretion, substances that are secreted, active secretion of - that is not the active color, let's change that to red - hydrogen ions.2437

Remember that the kidney plays an important role in homeostasis, and this includes the regulation of pH.2454

Secreting hydrogen ions into the tubule, those hydrogen ions will leave the body, and that will help maintain the pH of the body.2462

In fact, bicarbonate - one more thing here for reabsorption is bicarbonate - is passively reabsorbed. Hydrogen ions are secreted.2473

So, what you can see is that already the filtrate is much different than when it entered.2489

A lot of things have been picked up. Some things have been added.2493

In order to just keep the picture clear, I am going to go ahead now as we go into the loop of Henle, and let's start with a fresh picture of the nephrons.2500

So, we have done filtration in the glomerulus. Here is the proximal convoluted tubule.2508

Here is the loop of Henle.2514

The next segment that the filtrate is going to pass through is the descending loop of Henle, so descending loop of Henle right here.2518

And what is going on here is that there is additional water reabsorption. There are water channels called aquaporins, and these are water channels.2539

These are found in the descending loop of Henle, so water is being reabsorbed all along this descending loop of Henle.2554

Now, what we have here is H2O is reabsorbed. It is being put into the interstitial fluid, into the interstitium.2568

And ions and other substances are not reabsorbed.2583

The descending loop of Henle is fairly impermeable to ions and various other substances, so sodium is not reabsorbed, chloride, glucose- none of that.2588

The descending loop of Henle is permeable to water. Other substances such as ions are generally not reabsorbed here.2599

As you go deeper from cortex to medulla, there is a concentration gradient.2618

And this concentration gradient is in the interstitium. It is surrounding the renal tubule.2629

There are solutes out here, and as you go deeper from cortex to medulla, this solute concentration gets greater.2638

So, it starts out up here. There are solutes and then, greater and greater and greater and then, down here at the bottom, it is very concentrated.2647

What is driving the reabsorption of water in the kidney, or in the descending loop of Henle here in the collecting duct, as well, is this concentration gradient.2660

Without this concentration gradient, there would not be this drive for water to be reabsorbed.2673

As you go deeper and deeper into the medulla, the concentration of these solutes is greater.2684

So, even though water is leaving the tubule, and therefore, the fluid inside the tubule is becoming more concentrated,2697

water still wants to leave the tubule because the environment outside is still hyperosmolar to what is going on inside.2705

So, this filtrate is becoming more and more concentrated- a higher osmolarity.2712

However, out here is also becoming more and more concentrated, as well,2719

because of this gradient that has been generated that puts more solutes down into the medulla and fewer up by the cortex.2725

So, due to this concentration gradient, water is pulled towards the hyperosmolar environment outside the tubule.2740

Now, this situation for the ascending loop of Henle is very different than in the descending loop of Henle.2745

In the ascending loop of Henle, water is not reabsorbed. However, sodium chloride ions, are absorbed.2759

The channels here that make this permeable to water, those are not found here in the ascending loop of Henle.2773

The descending loop of Henle is permeable to water. The ascending loop of Henle is impermeable to water, permeable to sodium ions and chloride ions.2781

And in fact, the ascending loop of Henle has a very important job of maintaining. It maintains the concentration gradient from cortex to medulla.2798

Sodium chloride is transported passively. Sodium and chloride are transported passively down in the cortex, near the bottom of the loop, so the medulla.2819

So, down at the bottom of the loop of the Henle deep in the medulla, sodium and chloride are passively reabsorbed.2841

They are transported from the renal tubule to the interstitial area.2849

This movement of sodium chloride helps to maintain the concentration gradient that drives the reabsorption of water.2858

And as we go up the ascending loop of Henle in this region that is thicker...2867

It is thicker because these cells actually use more energy because the transport here of sodium is active as we go up here.2873

So, sodium and chloride are still transported, but now, we are talking about active transport of sodium as we go up the ascending loop of Henle.2883

Things to remember because I noticed a lot of information is that the descending loop of Henle, water is reabsorbed, ions are not.2895

The ascending loop of Henle maintains the concentration gradient going from cortex to medulla, and that is maintained by this reabsorption of sodium.2905

We are going to talk in a second about other ways in which this is maintained.2917

But, this sodium and chloride maintain the solute concentration out here in the interstitium.2920

Now, we get to this fluid that has made it through. We are now in the distal convoluted tubule.2926

What happens in the distal convoluted tubule? Well, some of the functions are the same as the proximal convoluted tubule.2932

Once again, we have sodium and chloride are reabsorbed. Potassium, I have not mentioned yet.2939

Potassium is, it can be reabsorbed or secreted in the proximal convoluted tubule.2952

Here in the distal convoluted tubule, potassium is actually passively secreted, and that removes excess potassium from the body.2960

Also, just like in the proximal convoluted tubule, hydrogen can be secreted.2972

One thing to note is that in the distal convoluted tubule, there is no reabsorption of glucose, amino acids, vitamins.2979

Those should have already been reabsorbed in the proximal convoluted tubule. Here, though, we have sodium chloride.2997

We have water following. We have secretion going on of things like hydrogen and potassium.3003

So, it is doing some of the same things such as a proximal convoluted tubule, but not all.3008

Finally, we get to the last segment of a nephron, which is the collecting duct.3013

Well, the permeability here, as far as water, varies, whereas, I said "oh, the descending loop of Henle is permeable to water".3019

The ascending loop of Henle is impermeable to water. The collecting duct is sometimes permeable to water.3027

And we are going to talk in a few minutes about the hormone ADH that controls3037

whether or not this collecting duct is reabsorbing water and how much it is reabsorbing.3043

But, assuming that the hormone, which is ADH, is acting on the collecting duct, then, these aquaporins are also found here in the collecting duct.3052

And if this ADH is acting on it, then, there is more aquaporins that end up in the cell membrane, and water can be reabsorbed.3064

If a person is dehydrated, then, the collecting duct can control the reabsorption of water, whereas here, it is not really a choice.3078

Here, impermeable to water, water reabsorption does not occur.3088

It occurs here. It does not occur here.3091

Here, it is a variable. It depends on the person's situation.3093

If they are dehydrated, they will absorb more water.3095

If they are fluid overloaded, then, these ducts will be closed, and they will not reabsorb water; and instead, that water will go out as part of the urine.3099

Another thing to note is that the latter part of the collecting duct is permeable to urea. Urea is reabsorbed here.3112

Now, you wonder why would urea be reabsorbed. Urea is a nitrogenous waste.3124

That is something we want to get out of our bodies. What is the point of reabsorbing that?3128

Well, there is very important reason, and that is because urea acts as another osmotically active substance,3133

as another solute essentially, to help maintain this concentration gradient.3141

I keep mentioning the concentration gradient because it is essential in concentrating the urine.3145

Without this concentration gradient, we could not produce hyperosmolar urine- urine that is more concentrated than our body fluids,3150

because this gradient is driving the reabsorption of water that I have been talking about.3157

And in addition to the sodium chloride that is reabsorbed at the ascending loop of Henle,3163

this urea reabsorbed at the collecting duct acts as a solute to help maintain this concentration gradient.3169

And actually, the urea is secreted. It is actually retaken up by the ascending loop of Henle.3177

You can think of it this way, the urea is reabsorbed. It ends up in this interstitial space here in the medulla.3189

It contributes to the osmolarity of the medulla, and then, after hanging out there a while, it is picked back up by the ascending loop of Henle.3198

And, it just makes this loop. Although, of course, some of it leaves the body in the urine.3208

The urine is going to contain hydrogen ions and ureas, potassium, other waste products, some water.3214

So, some urea will make its way out, but others, sometimes, are just recycled.3222

After going through all this, what we finally have is the urine. Remember that the urine leaves via the collecting duct.3229

It exits the kidney at the ureter, the two called the ureter, one in each kidney.3240

Those lead to the bladder, storage of urine in the bladder and then, exit from the body excreted.3245

The urine is excreted via the urethra.3254

In this next slide, I am going to focus more on the function of ADH.3257

And I am going to talk about another hormone that helps to regulate water and sodium uptake by the kidney.3262

Antidiuretic hormone is a hormone that is secreted by the posterior pituitary, which is up in the brain.3272

It is actually produced by a gland called the hypothalamus that we are going to cover in the endocrine section.3280

So, it is produced by the hypothalamus. However, it is stored in the posterior pituitary, which is right below the hypothalamus.3288

And it is secreted by the posterior pituitary. The trigger for secretion of this is an increase in osmolarity of the blood.3295

So, remember, the kidney has a very important role in the homeostasis including maintenance of the osmolarity- osmoregulation.3306

Talking a little bit about the function and the name here, it is antidiuretic hormone or ADH. You may hear this referred to also vasopressin.3316

What is a diuretic? Well, a diuretic is a substance that increases urination, increases urine output.3328

Caffeine, caffeinated drinks, coffee, caffeinated sodas, are diuretics. They increase the urine output.3338

Antidiuretic does the opposite. It decreases urine output, so it is antidiuretic.3346

It is against urine output, so it is decreasing urine output.3353

And what happens is if the body fluids become too concentrated, then, let's say for example, you had a bunch of salty chips.3359

You ate a bunch of chips. They have a lot of sodium in them, and then, you are going to have increased solutes in your bloodstream.3374

And therefore, your blood will have increased osmolarity.3383

The increased osmolarity will trigger the release of ADH by the posterior pituitary gland.3389

This is going to enter the bloodstream, so hormones. So they will enter its bloodstream, and it will act on the kidney.3399

What the kidney is going to do is kidney produces more concentrated urine, so less water will be lost in the urine- less water loss.3406

So, more concentrated urine meaning less water is lost, and therefore, if water is conserved, that will dilute out these solutes.3429

And the result will be that the osmolarity of the blood decreases.3440

And what is the mechanism by which this happens? Well, ADH acts on the collecting ducts and the distal convoluted tubule.3451

Recall that I said that the collecting ducts contain water channels- the aquaporins.3475

And what ADH does is it binds to receptors on the collecting duct.3483

And it triggers a cascade that results in an increase in the number of channels in the collecting duct.3489

The result is going to be increased water reabsorption and conservation of water, and their osmolarity will go down.3499

So, it is not triggered by just a loss of blood volume. It is specifically an increase in a concentration of the solutes in the blood:3521

increased osmolarity, release of ADH, kidney produces more concentrated urine and the osmolarity of blood will, therefore, decrease.3528

The second hormone that is very important in osmoregulation is aldosterone. Aldosterone is released by the adrenal cortex.3540

The adrenal glands, which in case you have not watched the endocrine section yet, are glands that are located right on top of the kidneys.3554

And one part of these glands is the adrenal cortex. It produces/releases aldosterone.3562

The trigger is a decrease in blood pressure or decrease in blood volume.3569

And aldosterone is one part of a system called the renin-angiotensin system, which is an important system in maintaining blood pressure.3574

So, let's just start from talking about this activation of this system.3587

There are sensors near the kidney, and they monitor blood pressure and blood volume.3592

If we have decreased blood pressure or decreased blood volume, then, this is detected by the sensors.3609

And in response, renin is released from the kidney.3619

There is a complex cascade that you do not need to know every step of or anything.3630

But, renin is part of a cascade that eventually allows for the cleavage of angiotensinogen, which is a precursor to angiotensin I.3635

Angiotensin I is converted to angiotensin II by an enzyme called ACE- angiotensin-converting enzyme.3661

Now, angiotensin II has two major effects. One is that it directly affects blood pressure.3679

It causes vasoconstriction. In other words, it causes the arteries to constrict.3687

That is going to increase the blood pressure directly.3694

So, if blood pressure is low, this system will trigger vasoconstriction - constriction of vessels - that will raise the pressure in the arteries.3698

A second effect that angiotensin II has is it triggers the adrenal cortex to release aldosterone.3708

What does aldosterone do? Well, aldosterone increases sodium reabsorption by the distal convoluted tubule.3721

Remember that where sodium goes, water will follow, so we have our nephron here, glomerulus.3739

And here in the distal convoluted tubule, if more sodium is being reabsorbed, chloride is going to follow, and water will follow.3750

This increased reabsorption of water is going to increase blood volume and blood pressure.3761

So, we are focusing on aldosterone here because we are talking about the excretory system.3775

But, this whole system helps maintain homeostasis also by angiotensin II vasoconstricting the vessels.3778

Now, one fairly common condition in westernized countries is high blood pressure/hypertension.3786

In other words, high blood pressure, which is a risk factor for stroke, for example.3797

So, in order to control high blood pressure, medications are sometimes used.3803

One of these is an ACE-inhibitor, so it is a medication that is blocking this enzyme.3806

Well, if you block this enzyme, and you block this step, angiotensin II will not exist.3814

It will not vasoconstrict, so blood vessels will remain dilated, and the pressure will be lower.3820

And aldosterone will not cause the retention of sodium in the fluid, so blood pressure will be lower.3825

There is another group of medications, and these are called ARBs, angiotensin receptor blockers, and what these do is they prevent the binding.3832

An ARB would act here, and it would prevent the binding of angiotensin II to receptors on the arteries. This is also a medication to treat hypertension.3846

So, you can see that this basic physiology actually has applications in medicine.3856

Now, we are going to review the lesson for today starting with example one: the figure below illustrates the nephron of an aquatic mammal.3863

And use the figure to explain why the loop of Henle in this mammal is shorter than the loop of Henle in terrestrial mammals.3874

The loop of Henle I showed before would be more like a human loop of Henle, so here is the aquatic animal, a shorter loop of Henle.3882

And then, the human or a typical terrestrial mammal loop of Henle would dip down farther into the medulla.3890

So, thinking about this, let's think about the environment of an aquatic animal. An aquatic mammal is exposed to water all the time.3900

So, it does not need to concentrate its urine as much as a mammal that lives on land especially a land animal that lives in a very dry environment.3915

In a desert environment, an animal will have an even longer loop of Henle, and the reason is,3923

remember that the ascending loop of Henle maintains the concentration gradient going from cortex to the medulla that allows urine to be concentrated.3928

To be more concentrated, it allows for this reabsorption of water. This concentration gradient allows for the reabsorption of water.3960

And the longer the loop of Henle is, the steeper the gradient can be. There is more distance here to pump out sodium chloride.3968

A mammal that has a lot of exposure to water may not need to concentrate its urine as much.3980

Whereas, especially an animal in a very dry environment like the desert, it is going to have to really minimize water loss and have a longer loop of Henle.3986

Example two: why do animals that live in a dry environment secrete, or actually it is excrete, nitrogenous waste in the form of uric acid?3998

Well, remember that there is a couple reasons.4010

In general, uric acid is less toxic than ammonia, so that is why it would be uric acid versus ammonia, but why not urea?4015

Well, dry environment is the key here.4022

Remember that uric acid is not water-soluble, and the big challenge in a dry environment is going to be water conservation.4024

Therefore, uric acid is excreted as a paste. It is not excreted in solution in urine.4035

By excreting it as a paste, the result is minimized water loss. Get rid of the nitrogenous waste with very little water loss.4050

Through what mechanisms do fish living in saltwater maintain their osmolarity below that of surrounding water.4064

Remember that a fish in saltwater is in a hyperosmolar environment. The challenge is going to be not getting dehydrated.4070

Water is trying to leave. Salt is trying to enter, so what this fish needs to do is conserve water, get rid of salt.4086

They do that a few ways. They drink a lot water.4097

Of course, this is seawater, so they are getting the water they need; but they are getting all the salt too, so they get rid of the salt.4101

They excrete salt via their gills, and this is through active transport. They also excrete salt via their kidneys, and they urinate only small amounts.4109

So, ways to prevent dehydration, ways to hold on to water and get rid of salt: drink a lot of water, and you are taking in a lot of salt, too,4131

so get rid of the salt by the gills, get rid of the salt via the kidneys, and kidneys reabsorb most of the water.4141

There is very little urine, and it is very concentrated.4150

Example three: on the figure below, indicate the following: 1. the section of the tubule that maintains the concentration gradient from cortex to medulla.4155

Here, we have the glomerulus, the proximal convoluted tubule. Now, here is the loop of Henle.4166

Remember that the loop of Henle maintains the concentration gradient, and particularly, it is the ascending loop of Henle. Therefore, no. 1 is this section.4172

It maintains this concentration gradient that allows for the reabsorption of water and the production of a hyperosmolar urine.4190

Two: the structure responsible for the reabsorption of glucose.4199

So, initially, blood is filtered by the glomerulus, and filtrate enters the proximal convoluted tubule.4203

In the proximal convoluted tubule, there are some things like glucose and amino acids and vitamins that we do not want to lose in the urine.4213

So, those are reabsorbed right here at this first section of the nephron.4223

The proximal convoluted tubule right here, no. 2, is the structure where reabsorption of glucose occurs.4229

Example four: a child contracts a gastrointestinal infection that causes severe diarrhea. As a result of this fluid loss, his blood pressure drops.4242

So, vomiting, bleeding, diarrhea, these can all cause fluid loss, and fluid loss, in turn, can cause a drop in blood pressure.4254

What hormone will be released to help maintain his blood pressure? By what mechanism will increase the child's blood pressure?4265

Well, remember those two hormones we talked about.4273

And the one that is triggered by a drop in blood pressure or blood volume, actually, is aldosterone.4275

Aldosterone is released by the adrenal glands in response to a drop in blood pressure or blood volume.4282

What is the mechanism of action? Well, aldosterone, remember, acts on the distal convoluted tubule.4291

And what it does is it increases the reabsorption of sodium, and water follows by osmosis.4301

So, more sodium is removed from the tubule back into the blood, and where a solute goes, water will follow.4317

That concludes this section of Educator.com on the excretory system.4327

Thank you for visiting.4332

Related Books

Related Books & Services

Educator®

Please sign in to participate in this lecture discussion.

Resetting Your Password?
or
Still having trouble? Contact us
OR

Start Learning Now

Our free lessons will get you started (Adobe Flash® required).
 Get immediate access to our entire library.

Membership Overview

  • Available 24/7. Unlimited Access to Our Entire Library.
  • Search and jump to exactly what you want to learn.
  • *Ask questions and get answers from the community and our teachers!
  • Practice questions with step-by-step solutions.
  • Download lecture slides for taking notes.
  • Track your course viewing progress.
  • Accessible anytime, anywhere with our Android and iOS apps.