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Dr. Carleen Eaton

Dr. Carleen Eaton

Natural Selection

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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
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Lecture Comments (9)

1 answer

Last reply by: Dr Carleen Eaton
Tue Jun 17, 2014 7:33 PM

Post by Maria Mohd Zarif on April 30, 2014

Do you think that the bacteria example is a good example for Natural Selection when the reason why bacteria becomes resistant is through mutation. And mutation is another mode for Evolution to occur. Right?

0 answers

Post by ramtin rezaei on November 16, 2013

What would be your opinion on the state of natural selection in modern human society? Are humans still experiencing natural selection in modern societies? Have the effects of natural selection been relaxed? Are we experiencing human guided selection now? Or are the traditional mechanisms of natural selection beginning to be replaced by modern day equivalents?

Any insights would be appreciated.
Cheers.

0 answers

Post by Ramitha Manivannan on January 24, 2013

I still don't understand Hardy Weinburg equations. Could you please explain it to me in very simple language?

Thanks!

1 answer

Last reply by: Dr Carleen Eaton
Thu Jan 17, 2013 6:49 PM

Post by Ramitha Manivannan on January 17, 2013

Dear Dr. Eaton,

Could I please have your email address so I can ask you questions?

Thanks,
Ramitha

1 answer

Last reply by: Dr Carleen Eaton
Mon Nov 12, 2012 6:34 PM

Post by John Weaver on October 28, 2012

are there any examples of added information in mutations?

0 answers

Post by JUNCHAO ZHANG on September 20, 2011

thank you! I understood SO MUCH better than what my teacher taught me.... :)

Natural Selection

  • While studying species during his voyage on the HMS Beagle, Darwin observed that:
    1. Individuals within a population vary in the traits that they possess.
    2. Species produce more offspring than can be supported by the environment and the offspring must compete for survival.
    3. Offspring inherit traits from their parents.
  • Darwin concluded that the offspring who possess favorable traits will have a higher probability of surviving and producing more offspring. Over many generations, these favorable traits will increase in the population.
  • Stabilizing selection selects for intermediate phenotypes and decreases the frequency of extreme phenotypes.
  • Directional selection results in an increase in the frequency of a phenotype at one extreme of a spectrum.
  • Disruptive selection results in an increase in the frequency of phenotypes at both extremes.

Natural Selection

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
  • Background 0:09
    • Work of Other Scientists
    • Aristotle
    • Carl Linnaeus
    • George Cuvier
    • James Hutton
    • Thomas Malthus
    • Jean-Baptiste Lamark
  • Darwin's Theory of Natural Selection 7:50
    • Evolution
    • Natural Selection
    • Charles Darwin & The Galapagos Islands
  • Genetic Variation 20:37
    • Mutations
    • Independent Assortment
    • Crossing Over
    • Random Fertilization
  • Natural Selection and the Peppered Moth 26:37
    • Natural Selection and the Peppered Moth
  • Types of Natural Selection 29:52
    • Directional Selection
    • Stabilizing Selection
    • Disruptive Selection
  • Sexual Selection 36:18
    • Sexual Dimorphism
    • Intersexual Selection
    • Intrasexual Selection
  • Evidence for Evolution 40:55
    • Paleontology: Fossil Record
    • Biogeography
    • Continental Drift
    • Pangaea
    • Marsupials
  • Homologous and Analogous Structure 50:10
    • Homologous Structure
    • Analogous Structure
  • 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

Transcription: Natural Selection

Welcome to Educator.com.0000

In this first in a series of lectures on evolution, we are going to talk about a very important mechanism of evolution, which is natural selection.0002

We are going to start with some background to give you context for Darwin's theory of natural selection.0010

Darwin lived from 1809 to 1882.0016

And his work was influenced by various scientists, thinkers and philosophers who came before him, as well as some scientists who were contemporaries of his.0020

We are going to go through the different findings and thoughts of those whose work may have0031

influenced Darwin starting way back, before we even get to Darwin- Aristotle's theory.0038

Aristotle lived in the 4th century B.C., and he had a very different view of things.0050

He stated that species were unchanging, so 4th century B.C., and he thought that species were unchanging.0055

In other words, he believed that species do not evolve.0067

He arranged organisms in a ladder of increasing complexity, and he called this scala naturae.0071

Not all philosophers agreed with Aristotle, though, and some believed that, in fact, species did change over time.0086

Let's go way forward to Carl Linnaeus, who lived in the 18th century.0094

And he actually developed the system of classification in nomenclature, so nomenclature means naming system.0106

And this system for naming of organisms is still in use today.0117

And this is the binomial system, whereby, each group of organisms has a name that is two parts using homo sapiens as an example.0125

The first part is the genus, and the second is the species, and we will talk more about this when we discuss phylogeny.0139

Linnaeus believed that the study of nature would reveal the divine order of the universe,0152

and that the similarities between species were the result of divine origins of creation.0158

So, he came at it from that perspective.0164

Georges Cuvier was a French palaeontologist in the late 18th and early 19 centuries, and he studied fossils.0168

And he determined that strata - strata are layers of earth, the singular is stratum - contained different fossils.0182

And so he noticed this change from layer to layer, so the bottom layers are the oldest and then, on up.0197

And he noticed that there were differences between the type of fossils in the layers, and he attributed this to catastrophes.0202

His thought was that catastrophes such as earthquakes or floods were responsible for these differences among strata.0209

Some flood comes along, wipes out many species.0217

And then, he believed that those species that had been wiped out were replaced by species that migrated in, moved in, from other areas.0221

He did not described changes in species as being due to evolution.0232

The work of Cuvier and others studying fossils influenced Darwin.0237

However, Darwin was also influenced by the ideas of scientists and thinkers who did believe that species could change overtime.0242

James Hutton was a Scottish geologist in the 18th century, and he proposed the theory of gradualism.0250

As you can see, it is not just naturalists whose work may have influenced Darwin, it is people from many different fields0260

so James Hutton, 18th century geologist, who published and proposed work on gradualism in 1795.0267

And what gradualism is relating to geology is a theory that suggested that the earth's geologic features such as mountains0280

and valleys were the result of cumulative slow changes0287

and that these changes were actually still taking place.0291

For example, a river over a long period of time could carve out a valley.0294

And he also believed that the earth was far older than was commonly thought during the time that he lived.0299

Thomas Malthus published a very famous essay in 1798, and this was the essay on the principle of population.0308

His work discussed the tendency of plant, animal and human populations to outgrow their resources.0322

And he attributed much of human suffering through a disease and famine to the fact0328

that there is this tendency for species to multiply beyond the resources that were available.0335

Jean-Baptiste Lamarck was also a contemporary of Darwin's, and he believed that species did evolve.0346

And he proposed his own theory on why this is- a mechanism for evolution.0355

His theory had two main ideas in it. One is the idea of use and disuse. The second is the idea of the inheritance of acquired characteristics.0362

And this was later proven to be incorrect, but it is a proposal for a mechanism on evolution.0382

So we are going to talk about this inheritance of acquired characteristics.0387

First of all, use and disuse: this is the idea that if a part of the body is used, it will develop. It will change.0394

And then, the second part is that this change that has taken place through use or disuse can be passed down to one's offspring.0400

We, now, know, of course, that changes that take place because of using a body part, like if you lifted weights and your arm muscles hypertrophy0410

- became very large -you are not going, then, have children who have these great big biceps.0421

So we know that now that acquired characteristics cannot be inherited; but at the time, this was not realized.0428

The classic example that Lamarck gave is that of the giraffe's neck.0436

He postulated that as giraffes reached, long ago ancestral giraffes were reaching for leaves high in the tree, it stretched their neck.0440

And then, when they had offspring, those offsprings had longer necks.0449

Those offspring, then, could reach even higher, stretch their necks a little more.0453

And that was passed along generation upon generation until eventually giraffes had very long necks.0458

And again, we, now, know that this is not correct, but it was a proposal to help explain how evolution occurs.0463

We are going to go on now and talk about Darwin's theory of natural selection.0472

But before we do, I want to make sure that you will understand exactly what evolution is.0475

Evolution is a change in the genetic composition of a population over time.0481

Natural selection is one mechanism for this. In a later lecture, we are going to talk about a couple other mechanisms such as genetic drift and gene flow.0487

Natural selection and evolution are not synonymous. Natural selection is a mechanism for evolution.0497

But what evolution is, is the change in the genetic composition of a population over time, so a change in the allele frequency.0503

A population starts out with a certain frequency for blue-eyed alleles.0510

And over many generations, that may change to where there is a much higher frequency of, say, brown-eyed alleles through evolution.0515

Darwin's theory was theory of natural selection. What does natural selection state?0524

Let's start with that and then, go back and talk a little bit about Darwin.0530

It states that individuals with traits that are beneficial to survival will be more likely to survive and produce offspring.0534

Over many generations, these traits will increase in frequency in the population.0542

Individuals with traits favorable to survival will have an increased chance of surviving and very importantly, reproducing.0550

And then, over many generations, these traits will increase in frequency in the population.0583

Charles Darwin actually started out in medical school, so he entered medical school, realized he did not like it; and instead, he wanted to be a naturalist.0620

He wanted to just go out and study the natural world, so when he was 22, he embarked on a voyage on the HMS Beagle.0629

This ship departed from England, travelled along the coast of South America to Australia and Africa.0636

And it also visited some islands off the coast of South America called the Galapagos Islands.0642

During these travels, Darwin carefully observed the species that he saw.0652

He noticed similarities. He noticed the differences between them, and these observations inspired his theory of natural selection.0657

Focusing on the Galapagos Islands, when he was there,0665

what he noted is that while the birds he saw there had similarities, they actually had differences, as well.0668

And these differences allowed them to be extremely well-adapted to their environment.0674

For example, looking at some finches, they were finches.0679

They had a lot of similarities, but if you looked carefully, you would notice that their beaks were slightly different.0685

Their beaks were specialized to take advantage of the different food sources on the island.0690

One finch may have had a longer, pointier, narrower beak that would allow it to capture insects.0695

Another might have a blunter, stronger, larger beak that would allow it to crack seeds open.0702

So, he noted that there were variations among the species that allowed them to be very well-adapted to their environment.0708

Darwin developed a theory based on this, and he called this theory descent with modification.0719

It should be noted that Alfred Russell Wallace, who was also a British naturalist, developed on his own a theory of natural selection, as well.0738

And Wallace's findings were presented in a paper in 1858.0748

But in 1859, Darwin published a much more extensive discussion of the theory of natural0752

selection in his book titled "On the Origin of Species by Means of Natural Selection".0759

Commonly, it is just called "The Origin of Species", so his book "On the Origin of Species by Means of Natural Selection".0765

Let's think or talk more about Darwin's observations. Darwin observed several things.0782

He observed the individuals within a population vary in the traits that they possessed.0805

Looking around at the human population, short people, taller people, curly hair, straight hair,0823

different hair colors, different eye colors, it is just an endless array of traits within the population.0829

And the same is true of any species that you would look at- just about.0834

His second observation is that species produce more offspring than can be supported by the environment0839

and that the offspring must compete for survival, and you can see Malthus' influence here.0846

Summing this up, species produce more offspring than the environment can support.0852

And therefore, these individuals must compete for survival. I will just put "must compete".0870

If there is only so much food available in a habitat, then, the organisms there are going to have to compete for that food or other resources.0876

Finally, Darwin observed that offspring inherit traits from their parents.0888

From these observations, Darwin concluded that offspring who possess traits favorable to0911

survival will have a higher probability of living, surviving and producing more offspring.0917

These offspring will possess that traits they receive from their parents, as well as what we now know with modern genetics are the alleles and genes.0924

And they will pass those traits on to those offspring.0933

A higher chance of survival with favorable traits, so there is variation within a population.0937

Certain individuals will have a survival advantage through those certain traits. They will have a better chance of living longer, mating, producing offspring.0941

The offspring will have those traits. Over many, many generations, these favorable traits will increase in frequency in a population.0949

Importantly, the result of natural selection is that organisms become better adapted to their environments over time.0959

So, while there are other mechanisms of evolution, natural selection is the only one that allows population to become better adapted to their environments.0965

And I want to be clear that evolution and natural selection is something that occurs in populations, not individuals.0973

An individual has whatever traits she has, whatever genes she has.0982

It is the population that changes over time, so it is populations that are affected by natural selection; and it is populations that evolve, not individuals.0989

Let's go back to Darwin's finches. Darwin observed that finches that eat insects have more of a longer, narrow, pointed-type beak.0999

It makes sense that if there are insects available as a food source, those individuals out of the finch1010

population that happened to have a pointier beak, might be able to catch a beetle better or something.1016

Then, if they have food, they are going to survive.1022

They are going to have offspring, and those birds that are their offspring are going to tend to have the pointier beaks like their parents.1025

And if this continues to happen over many, many generations, the finch population will have longer, pointier, narrower beaks.1033

Maybe a bird with a flatter beak, then, cannot feed as well, cannot catch the insects. They do not survive as long.1043

They do not pass along their genes, and the flatter beak does not survive.1049

However, let's say that on this island, there is a disease going through the insect population, and the number of insects available decreases.1056

Well, there is still some variation of population, and perhaps then, those individuals who do have somewhat of a flatter,1067

stronger beak, those individuals, then, might be able to utilize another food source better like, say, seeds.1076

Then, selection can move the population towards having flatter, stronger beaks.1084

As those individuals eat seeds, they survive better than the insect-eating ones. Now, the food source has changed.1091

The flatter-beaked birds leave more offspring. Those offspring carry that trait of flatter beaks and so on.1097

So, you can see how variation is extremely important and essential to natural selection1104

because if there is no variation in traits, there cannot be differential survival.1108

Looking, now, at the giraffe example from a natural selection perspective,1116

so Lamarck’s theory would say that the giraffes had to reach up high for leaves that stretch their necks.1120

They pass along these longer necks to offspring.1129

Well, we, now, know that that is not how it occurred. How would natural selection explain the evolution of longer necks in giraffes?1131

Well, there must have been some survival advantage for longer necks.1139

It may have been that those giraffes with longer necks could reach the leaves better, and therefore, they were more likely to survive.1143

They left more offsprings who had genes and alleles that coded for longer necks, so their offspring tended to have longer necks.1154

Those offspring tended to survive.1163

They passed along their alleles, and over many, many generations, the frequency of the alleles for longer necks increased in the population.1166

Actually, scientists are not in agreement if longer necks are selected for due to the fact that giraffes could reach these leaves that are high out.1175

There may be other reasons.1186

But in any case, whatever the reason was, it probably had to do with increased survival or leaving more offspring, and thus, selecting for those individuals.1191

As I mentioned, in order for this to occur, there has to be variation in traits.1202

There needs to be genetic variation among the population- some giraffes with shorter necks, some with longer,1206

some birds with narrower beaks, some with wider, flatter beaks and differential survival and number of offspring.1211

So, let's go ahead and review some mechanisms of genetic variation.1220

To cover this in detail, you should go back and watch the lectures on molecular genetics, Mendelian genetics,1224

where we talked in great detail about how this all works but for now, just really reviewing mechanisms of genetic variation.1231

It is important to remember that mutations are the ultimate source of genetic variation.1240

That is how new traits could be introduced into a population.1244

Recall that mutations are changes in the DNA sequence.1249

And ultimately, that is where all these differences and traits in alleles come from and where brand new variation on the trait could come from.1256

But what are some ways in which these genes get mixed and matched, and we have organisms with a huge variety of phenotypes and mixture of traits?1265

Well, recall the law of independent assortment, and we talked about this in Mendelian genetics.1278

The law of independent assortment states that alleles for a particular trait assort independently of alleles for other traits.1284

Alleles for traits assort independently of one another, of alleles for other traits, so let's start with that.1293

This is a review, here, of meiosis, and the purple chromosomes are going to be the ones that are maternally derived.1314

The green are going to be paternally derived.1325

We have an individual here, and we will say that this is a male and that gamete formation - so in this case, sperm formation - is occurring.1328

And this individual is diploid. They have two copies of each chromosome.1338

Here, we have chromosome no. 1 from this individual's mother, chromosome no. 1 from this individual's father,1343

chromosome 2 and chromosome 2 from the mother and from the father.1352

Now, let's say that height is carried on chromosome 1.1357

Let's say that that carries the genes for height, and let's say that on chromosome 2, eye color is carried.1365

OK, now, let's say this individual's mother gave this individual a gene to be tall, and the father gave this individual the allele to be short.1377

The mother gave blue eyes, the blue eye color allele. The father gave the brown eye color allele.1391

Now, in meiosis, in that first division, meiosis 1, homologous pairs of chromosomes separate.1400

And here, we see this cell got chromosome 1 that was maternally derived and chromosome 2 that was paternally derived.1410

This one got chromosome 1 paternally derived and chromosome 2 maternally derived.1420

Independent assortment states that this just as easily could have happened the other way around.1426

It was completely random that the purple chromosome 1 ended up here with the green chromosome 2.1430

It just as is it could have been that chromosome 1 and 2, the maternally derived stayed together.1435

So, where tall and short go have nothing to do with where brown and blue go, so this is independent assortment.1442

And that means that the gametes have all sorts of mixtures.1448

This individual will have the tall allele with brown eyes, tall, brown, and even here, we have short with blue; but it could have been the other way around.1452

It could have been that tall was with blue.1476

Now, this simplifies it a bit because what it does not show is crossing over.1481

And now, we are going to talk about that because that is another mechanism for variation.1488

Recall that during prophase 1 of meiosis, crossing over occurs. Homologous chromosomes pair up and exchange homologous segments of DNA.1493

Actually, this tall gene could have ended up being swapped and ended up on the paternal chromosome.1506

And the short could have ended up on the maternal chromosome.1513

And there is all these other paternally derived alleles, but now, they are with the tall from the mother, from the maternally derived chromosome.1515

Crossing over is another source of genetic variation.1522

Finally, sexual reproduction and random fertilization is a mechanism for genetic variation offspring.1526

So, the fact that the chromosomes from two individuals are coming together is going to create a unique mix of traits.1536

Here, we are saying that this is a male, so these are sperm. These sperm can randomly unite with an egg.1546

So, we have sperm that contain - if you put them together - literally millions of combinations of alleles and then,1554

eggs that contain millions of combinations of alleles and mixes of traits.1560

Those two are united, and that is why siblings do not all look the same.1566

They each have a different mix depending on which alleles they got from the mother, which they got from the father and how those came together.1572

There is just an enormous diversity of individuals with different traits, and some of those traits may be more favorable in a particular environment.1578

And those individuals have a greater chance of surviving and producing offspring and passing on their traits, their alleles.1587

Natural selection can best be understood through example, so this is a classic example.1598

It is the case of the peppered moth, and prior to the mid-1800s, looking in England, almost all peppered moths were light-colored with dark flaps.1604

So, this is the light-colored peppered moth that you see, and the reason it is called "peppered" is there are some of these dark flaps.1617

And you can see how this moth could blend in well, with, say, bark on a tree or a rock, being this color.1622

Well, an interesting happened during the mid-1800s in England.1634

This was the industrial revolution, and cities became extremely polluted.1641

There was not a pollution control like we have now, so the cities were just full of soot, and this soot, sort of, layered everything and made it dark.1646

And what was noticed is that there were very few of these light-colored peppered moths left.1656

Instead, a dark variant, which prior to this had been rare, came to predominate- greatly increased.1662

When the soot covered the trees, if a moth would land on the tree and it was light-colored, a bird could see it.1670

A predator could see it. It would eat it.1676

This moth would not survive.1678

There was occasionally some dark-variant moths in the population.1681

Those individuals would blend in with that tree, would not be eaten by a bird, would reproduce, and their offspring will be more likely to be dark-colored.1687

They would survive, pass on these dark alleles, and within just a few generations, this dark allele came to predominate.1696

And almost every moth in these polluted, industrial areas were dark-colored.1704

But if you went outside, you went out to the countryside and looked for peppered moths, what you would see is that the vast majority were light-colored1711

because out in the country where the trees were not blackened, a dark moth like this would stand out against this background.1718

This is an example of natural selection, selecting for coloration on a moth depending on the environment.1724

Another example and an example that is a huge issue in modern times is that of drug-resistance.1733

As antibiotics have become increasingly commonly used, bacteria that carry genes for drug-resistance have been selected for.1738

They survive. They pass on their DNA to their offspring.1747

Those offspring are resistant, so now, we might try a medication for, say, an ear infection.1750

And all those bacteria in the person's ear that are susceptible to the antibiotic will die off.1758

But those few that are resisting can survive, and then, sometimes, we have to try a second antibiotic that will kill those remaining bacteria,1764

but then, we are risking now, we are selecting for some bacteria to be resistant to that second line drug.1774

So, we have to keep coming up with more and more drugs to stay ahead of this natural selection that is occurring in the bacterial population.1779

OK, right now, we have been talking natural selection in general, but you can break down natural selection into different subtypes.1788

Here, you can see three subtypes. The first that I am going to talk about is stabilizing selection here in the middle.1795

And the Y axis represents, the number of individuals with that particular type of trait.1812

Here, we have the trait or phenotype, and it can be quantified different ways depending on what trait we are talking about.1822

With stabilizing selection, the example I am going to use is human birth weight.1830

So the phenotype here is going to be birth weight; and it is going to be from 0 to, let's say, 10 pounds.1834

Stabilizing selection, first of all, favors intermediate phenotypes and decreases the frequency of extreme phenotypes.1849

Stabilizing selection favors intermediate phenotypes, so it maintains the status quo. It stabilizes the situation.1856

It turns out that babies who have a relatively low birth weight, and those who have a1873

relatively high birth weight are at an increased...they have a greater mortality rate.1877

So, the best chance of survival for a human new born is to have an intermediate birth weight.1884

Intermediate is defined as from 6.5 to about 8.5 pounds.1890

Now, if you look at the gold line, that would be the population before selection has acted on it, and you see a broader spread here of birth weights.1898

What happens is, though, if babies that are 6.5 to 8.5 pounds at birth have a favorable survival,1910

that phenotype will increase in the population as those individuals are selected for over many generations.1918

So, what we see now in the blue line, this is before. It is the gold line, and then, after selection, we see an increase in the number of individuals.1925

The frequency of this phenotype, who were in this range of 6.5, actually 8.5, 6.5 to 8.5 would be right here at this peak.1936

Those individuals are selected for. Individuals at either end, either extreme low or high birth weight, are selected against.1950

So, stabilizing selection favors the intermediate phenotypes.1958

Directional selection is at the top. This is selection in favor of a particular phenotype with the result that alleles for that phenotype will increase in frequency,1964

so selection in favor of a phenotype, I will say, at one extreme. That is what they mean "in one direction".1979

Here, we could use the example of the moths that we just talked about.1996

Here, we are going to have the phenotype that we are looking at, the moth color, and we can quantify this however we want.1999

And I am just going to say the light is here, and then, dark is here.2008

And a very, very light moth that is bright white would probably stand out, not have a great chance of survival.2015

But before the soot and that selection pressure, the peak might have been here, which is the classic light-colored pepper moth.2021

Then, when the soot occurred in the environment, these darker moths got selected for2029

as you can see a shift in the population towards increased frequency of the darker phenotypes, so it is in one direction.2035

Directional selection could occur in the opposite.2043

If the environment become colder and snowier, then, individuals who are almost white or white, who can blend in with the snow, could then, be selected for.2046

So, directional selection could have worked in either selection.2058

Disruptive selection is the third type. It is the third pattern of selection.2062

This is, kind of, an interesting one because it favors phenotypes at both extremes, so how could this work?2069

Well, let's say that a species of squirrel could be either very light brown, medium brown or dark brown.2087

OK, so we have color, and we have, again, light to dark; and this is going to be squirrel coat color.2096

But this squirrel lives in an area where two types of trees predominate: light brown and very dark brown trees.2104

But there are not many of intermediate color.2114

What could happen is, then, the very light-colored squirrels could be camouflaged against these trees.2117

The very dark-colored squirrels could be camouflaged against that trees.2124

But those squirrels with the intermediate coloration will not blend in as well and get eaten by predators.2128

In this case, we see what is called disruptive selection, where there is two peaks.2133

And these are at the extreme; and the intermediate phenotype becomes less common.2138

This type of selection, then, favors genetic variation.2144

The thing about disruptive selection is it increases the genetic variation in a population.2151

Three types of selection: stabilizing that favors the intermediate phenotype; directional that favors selection for one the extremes in one direction;2163

and disruptive, where there is two peaks, the two extreme phenotypes are selected for.2173

We are going to talk about another type of natural selection, and this is sexual selection.2180

In this case, characteristics that increase an individual's chance of mating and, thus, producing offspring are selected for.2185

And remember that natural selection increase in the frequency of those traits that allow an individual to survive and produce more offspring.2193

It is the producing more offspring that allows those alleles to be passed on.2205

So one way to ensure that an individual produces more offspring is that that individual survives in the first place.2209

They are better at catching food. They are bigger and stronger, and they can evade predators.2216

So, just merely surviving will increase one's chance of reproducing.2220

Selection, though, can also work on traits that just focus on the chances of mating and reproducing and not surviving.2224

You need both, but sexual selection really focuses on the mating and reproduction aspect.2232

Sexual selection, then, refers to selection of characteristics that increase the chance of attracting a mate.2242

The term sexual dimorphism refers to a difference in appearance between males and females in a species.2250

For some species, you cannot tell the males and the females apart, but for many, you can.2260

If you look at peacocks, the male peacock has large, brightly-colored feathers.2266

The female peacock is much more drab looking, blends into the background better, same with a lot of species of birds.2271

If we talk about intersexual selection, we are talking about one sex choosing a mate of the opposite sex based on certain characteristics.2278

So one sex chooses a mate based on certain characteristics.2294

Usually, the females are selecting the mate, and for example, a male bird who has brighter feathers might be more likely to attract a mate.2307

He will, then, pass along that trait of brighter feather color. Those offspring will have a brighter feather color.2321

They will be more successful attracting mates, and you can see how over many, many generations, male birds could evolve to have brighter feather colors.2328

So, it does not help them to survive per se, to catch food or anything, and in fact, it can be a disadvantage because they could be targeted by predators.2337

But they have an advantage in selection because they are more likely to mate and produce offspring, so this is intersexual selection.2345

It involves one sex choosing a mate of the other sex. There can also be sexual selection that involves intrasexual selection, and this is selection within a sex.2356

And this really has to do with competition also for mates.2377

Lions live in prides where there is usually, say, three or four females per one male.2386

A small pride will just have one male and a few females. A larger pride could have two males, but then, there is going to be, say, six or eight females.2391

Now, once the male offspring come to maturity, they get kicked out of the pride, and they need to go take over a pride from another lion.2400

And in order to take over a pride, the male lion needs to be large.2408

Therefore, a larger, stronger male is going to have a better chance of taking over a pride,2413

mating with the females in that pride and passing along his traits including larger size.2420

So, this time, it is not a female choosing a male.2425

It is males competing against males, but it still has to do with chances of mating, so this is intrasexual selection versus intersexual selection.2428

Again, sexual selection is just a subtype of natural selection that has to do with characteristics2436

that increase an individual's chance of mating, reproducing and passing along their alleles.2442

Now, we have talked about what evolution is and the mechanism of natural selection.2449

What we are going to discuss next is some evidence for evolution.2454

So lines of evidence come from many fields: paleontology, biogeography, comparative anatomy, embryology and molecular biology.2458

One that is not listed here but that is important, as well, is observation.2469

We talked about the example of the peppered moths, which occurred relatively rapidly.2474

And experiments have been done to, sort of, repeat that and see what happens.2479

And we have been able to observe natural selection at work, evolution at work, so observation also provided evidence.2484

Now, we are going to talk about paleontology and studying the fossil record.2491

The fossil record provides some good evidence for evolution, but to understand that evidence, we need to talk about how fossils are dated.2502

Radioactive or radiometric - so radioactive also called radiometric dating - is a method used to determine how old fossils are.2514

Recall in the lecture on chemistry at the beginning of this course, we talked about half-life.2528

And half-life is the amount of time required for half of an isotope to decay.2534

We are going to focus on carbon dating, and carbon dating is a type of radioactive dating that is based on the half-life of carbon.2541

And it can be used to date organisms that were once alive.2547

C-14/carbon-14 is a radioisotope, so it is a radioactive form of carbon, whereas, C-12 and C-13 are stable. They are stable isotopes.2551

And recall that radioisotopes spontaneously decay. They are unstable.2568

They give off energy, and carbon-14 decays to nitrogen.2572

What scientists do is they can look at the ratio of C-14 to C-12, and use that information to determine2582

how old something that they have found that was once living, how old that is, how old that fossil is.2595

The amount of C-14 is going to decline over time as it decays into nitrogen, and that allows us to determine the age of a fossil.2604

Carbon has a half-life of about 5730 years. That means that in 5730 years, half of the C-14 will be gone.2613

Wait another 5700 years, half of that remaining amount will be gone and so on.2628

In about 10 half-lives, the C-14 will be almost gone, and that means that we cannot use carbon dating for fossils that are very, very old.2635

We need to use something that has an older half-life, but this gives you an idea of how radiometric dating is done.2646

And based on radiometric dating, the earth is believed to be about 4.6 billion years old.2657

Now, we talked about how fossils are dated, how does the fossil record support evolution?2670

Well, even though the fossil record is incomplete, it does give us some good evidence.2676

What we see in the fossil record is the appearance of new types of organisms and the disappearance of other types of organisms such as the dinosaurs.2679

It also shows changes that organisms have undergone over time.2689

And the fossil record can show us links between modern organisms and their ancient ancestors.2693

Horse evolution, we have a particularly good record of that.2699

A lot of intermediate fossils have been found to show links between the ancient ancestor,2705

a species from the genus hyracotherium and the modern horse genus equus.2711

We have found in the fossil record many links between these two that helped us see how evolution may have occurred.2726

That was paleontology. The next area that can provide support for evolution is biogeography.2736

Biogeography is a field that dedicates itself to the study of geographic distribution of organisms.2744

Continental drift refers to the slow movement of continents over a very long period of time.2767

At one time, the earth had only a single continent called Pangaea, so this was a single large continent.2789

Approximately 200 million years ago, this continent separated out into multiple continents, and the result is the separate continents that we have today.2801

Now, we would expect, if evolution is correct, that if a species evolved after the separation of the continents, that species would only be present2814

on a particular continent rather than being distributed evenly all over the face of the earth, and in fact, we do have many examples to that.2823

Marsupials - when we talk about the diversity of life, we will talk about marsupials - are nearly only found in Australia, and Australia lacks placental mammals.2832

So, they have marsupial mammals.2844

And these are different placental mammals because in marsupials, offspring are born as embryos and then, finish their development in the pouch, like in a kangaroo.2846

And in Australia, there is a huge diversity of marsupials that have filled different niches in the environment, but no natural population of placental mammals.2858

And this makes sense given that Australia has been isolated from the other continents for many millions of years, and marsupials evolved there.2869

In other isolated areas such as the Hawaiian islands, we also see species such as bird species that are not found anywhere else.2880

And actually the Hawaiian islands lacked large land mammals prior to the arrival of humans.2889

The species that are unique to an area like this and that evolved there are called endemic species.2895

These species are unique to that area, and instead of seeing that "OK, similar environments have the same species". We do not see this.2902

In fact, two tropical islands far apart do not have the same species.2910

Even though they have the same climate, they may have species that have some superficially similar features,2914

which we will talk about in a minute, but they are not closely-related species.2923

They are not the same species.2926

Often, what you will see is that species found on an island are more closely-related to animals2929

on the nearby mainland than they are to far away but similar environment type islands.2934

Again, this is some evidence that these populations evolved separately from each other because they were isolated from each other.2944

So, that is paleontology and biogeography we covered. Now, we are going to jump over to embryology.2953

We will do comparative anatomy in a minute.2959

When we compare the developing embryos of different organisms, we can find some evidence,2961

some support for the idea that species evolved from a common ancestor.2967

For example, if you look at a fish embryo, a human and a bird, at some point of development, they all have gill slits and a tail.2972

These go on to develop into different structures, into different species.2980

But as they are going through that development, you can see this possible evidence of a common ancestor.2984

Finally, molecular biology, if we look at the DNA sequence in different organisms,2992

the more closely-related two species are, the more similar their DNA sequence is.2999

Comparative anatomy is going to be our next topic under evidence of evolution.3005

Well, first of all, anatomy is the study of the structure of organisms.3014

Comparative anatomy is the study of similarities and differences among the anatomy of organisms.3020

Homologous structures are structures that are similar, but they have similarities in underlying structure but different functions.3028

So, why would they even have similarities in structure? Because these organisms evolved from a common ancestor.3041

Homologous structures: similar due to evolution to evolving from a common ancestor.3049

These are structures with different functions, but similar underlying structure due to evolution from a common ancestor.3069

A classic example: if we look at the arm of a human, the flipper of a whale, the wing of a bat and the leg of a dog, there are similarities in structure.3077

Here, we have the large bone, the humerus. We can see the counterpart here in the whale fin, the bat wing and the dog leg.3091

Next, are two bones, the radius and ulna right here, here. The bat, this bone here actually forks so right there and the dog.3099

Next, we see the series of smaller bones at the wrist, and continuing on down, you can see the structural similarity in these digits.3111

Why would there be similarities between structures with such different functions?3125

Well, one possibility is that all these individuals evolved from a common ancestor, but due to selection pressure, they developed differences to survive.3129

It is believed that whales evolved from an ancestor that was on land, so whales had selection pressure to be able to survive in the ocean,3139

to be able to swim well, whereas, a bat faced different selection pressures in its environment; and these all diverged into different structures.3148

So, this is an example of homologous structures from species that evolved from a common ancestor but came to live in different environments.3156

Now, analogous structures have the same function but a different structure,3170

so homologous, same structure, different function, common ancestor, not exactly the same but similarities in structure.3177

But I will just put same structure, different function, common ancestor. That is homologous.3190

Analogous would be...so it is a different function. Now, in analogous, we have same function, different structure, no recent common ancestor.3202

I will just put "no common ancestor", but no recent common ancestor. It might be a little more precise- no common ancestor.3223

Example would be the wings of birds and wings of insects.3231

These two types of organisms do not have a recent common ancestor. Yet, they both have wings.3247

Those wings have the same function.3254

They allow for flight, but they evolved completely separate paths and got to a similar place but through different paths.3256

And the structures of the wings are not very similar.3265

This is due to adaptive solutions to certain environmental situations.3269

So similar environmental pressures resulted in structures that carry out the same functions.3276

Homologous: similar structure, different function, common ancestor.3281

Analogous: different structure, similar function, no common ancestor.3285

While we are talking about anatomy and structures, you should also be familiar with the vestigial structures.3292

These are a vestiges or remnants of structures from an ancestor, but these are just, like I said, remnants.3298

They are not useful. An example would be the pelvis of a whale.3307

Whales do not walk. They do not really need a pelvis, but for some reason, they have a pelvis.3312

Well, one possibility is that the pelvis is a remnant of a fully functional structure from its ancestor.3315

And that structure was useful in the ancestor; but it is just, sort of, left over from that.3323

The appendix...so the pelvis in the whale, another one is in humans, the appendix.3327

In humans, the appendix does not have a function that we know of.3332

It is a little outpouching attached to the intestine, and it can cause problems and needs to be removed but does not really have an important function.3335

And it is thought, though, that in ancestral species that had a much more plant-based diet, the function of the appendix was in digestion.3346

There are some species of blind fish that have eyes.3356

Again, those eyes are not useful to them, but to ancestor of theirs, they may have been useful; and they are just remnants of vestiges.3361

Alright, so now that we have discussed natural selection and some different patterns of evolution of natural selection,3369

we are going to go ahead and do some examples.3375

Example one: why is genetic variation within a population essential for natural selection? Why do we have to have genetic variation?3377

Well, remember that natural selection is based on different rates of survival and production of offspring.3386

Therefore, in order for it to occur, there has to be traits that provide a survival advantage to some individuals in the population.3396

OK, there must be traits that provide a survival advantage.3407

If there are not, if all individuals have the exact same traits, there would be no difference in survival. There would be no way for natural selection to act.3421

Traits that increase survival and number of offspring increase in frequency in the population over many generations.3431

Without differences in traits, there would be no way for species to adapt to changes in the environment.3458

There would not be differential survival like in the case of the peppered moth.3465

If there was no variation, if there were all light-peppered moths, there were no dark moths at all,3469

when the soot came, then, all those light moths would have been killed.3475

Eventually, the species would probably have just died out completely. There would have been no way for the species as a whole to adapt.3479

Example two: a population of birds lives in an area where a new predator has recently become established.3488

The smallest birds are able to evade the predator by hiding, and the largest birds can fight off the predator.3495

Which graph below represents the type of selection that will likely take place? What is the name of this type of selection?3501

So, in this case, what we see, here is some selection graphs, and this is going to be the number of individuals on the Y axis.3509

And on the X axis, we are going to have the trait or the phenotype.3517

And what is happening is the smallest birds are going to be selected for because they can evade the predator.3521

The largest birds can fight off the predator, but those birds of intermediate size will probably get killed off, so the smallest and the largest will survive.3528

They will have offspring, and those traits will increase in frequency in the population.3538

So, what I am looking for is a type of selection that favors small and large birds but not intermediate types.3543

The gold, to remember, is the before in the graphs that we are using. The blue if after.3549

And the one that I see that is favoring extreme phenotypes, so if we are going to say size from small to large, here, small and large are being favored.3555

And recall that the name of this is disruptive selection.3570

Here, recall this is directional selection. The phenotype at one extreme is being selected for.3579

It is moving the population in this direction, just in one direction, though, not two.3586

Finally, we have stabilizing selection, and this is going to favor the intermediate phenotype.3592

So we are going to end up with individuals that are medium size being favored.3601

The correct answer is disruptive selection, which is this graph right here.3607

Example three: list three mechanisms by which genetic variation is maintained within a population.3615

Well, new mutations introduce new genotypes into the population.3622

Two: crossing over. Crossing over allows a mix between alleles, paternally derived and those that are maternally derived, during gamete formation.3631

We need three. A third could be independent assortment, whereas, the alleles for one trait3644

assort independently from the alleles of another trait unless, of course, there is linkage, which is given in detail in an early lecture.3651

You were just asked for three. Here is a fourth, though- random fertilization, so four mechanisms that maintain genetic variation within a population.3659

So natural selection is possibly pressuring for a particular phenotype with an associated genotype.3672

But yet, genetic variation can be maintained through various mechanisms.3685

OK, explain the difference between homologous and analogous structures.3688

Homologous structures: these are similar structures, so similarities in the structure but different functions.3696

And this is due to descent or evolution from a common ancestor.3719

And the example I gave was the flipper of a whale, the wing of a bat, the human arm, dog leg.3734

Those all have very different functions.3743

But they have some structural similarities that are thought to be due to the fact that all those species way back had a common ancestor.3745

Analogous structures: analogous structure, similar structure for homologous.3753

So, analogous structure, we have different underlying structure, but the same or similar function; and they evolved separately.3760

They evolved independently. Example I gave is the wings of a bat, or excuse me, the wings of a bird or a bat and the wings of an insect.3780

Those are both wings. They have similar function, very different structure.3790

And they evolved along separate lines so homologous versus analogous structures.3796

That concludes this lecture on natural selection.3803

Thanks for visiting Educator.com3806

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