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Evolution

Chapter 22: Descent with Modification 


  • Relative dating is a method of comparing the ages of two fossils by comparing their placement in rock layers

  • Artificial selection is the selective breeding of plants and animals to produce animals to produce desirable traits in offspring

  • Inheritance of Acquired Characteristics: modifications can be passed on to offspring

  • Natural Selection: the process by which organisms with variation most suited to their environment to survive and leave more offspring 

  • Fitness: How well an organism can survive and reproduce in its environment. 

Evidence for Evolution: 

  1. Direct Observation 

Ex. Insect populations become resistant to pesticides Antibiotic-resistant bacteria 

  1. Fossil Record

  2. Homology: characteristics in related species can have underlying similarities even though functions may differ

Ex. Homologous structures: similar anatomy from common ancestors 

Embryonic homologies: similar early development 

Vestigial Organs: Structures with little to no use

Molecular homologies: similar DNA and amino acid

  1. Biogeography: Geographic distribution of a species 

Ex. Continental drift and Pangaea explain similarities on different continents. 

Convergent evolution: Distantly related species can resemble one another Similar problem, similar solutions

Ex. Torpedo shape of sharks, penguins, and dolphins 

Divergent Evolution: Where you diverge/move away from common ancestors 

Ex. Humans diverging from the monkeys 


Chapter 23: Evolution of Populations

  • Microevolution: change in allele frequencies of a population over generations

  • Evolution is based on genetic variation

  • Point mutations: changes in one base (eg. sickle cell)

  • Chromosomal mutations: delete, duplicate, disrupt, rearrange

  • Sexual recombination: contributes to most of the genetic variation in a population (Crossing over, independent assortment, random fertilization)

  • Population genetics: study of how populations change genetically over time

  • Population: a group of individuals that live in the same area and interbreed, producing fertile offspring

  • Gene pool: all of the alleles for all genes in all the members of a population

  • Fixed allele: all members of a population only have 1 allele for a particular trait

  • Hardy-Weinberg Principle: the allele and genotype frequencies of a population will remain constant from generation to generation

  • Equilibrium + allele and genotype frequencies remain constant

  • CONDITIONS FOR HARDY-WEINBERG EQUILIBRIUM

  1. No mutations

  2. Random mating

  3. No natural selection

  4. Large population size

  5. No gene flow

  • If at least one of these conditions is NOT met, then the population is EVOLVING

  • Allele frequencies: a gene with 2 alleles: p, q

p = frequency of dominant allele (A)

q = frequency of recessive allele (a)

p + q = 1

USE DECIMALS

  • Genotype frequencies: 3 genotypes (AA, Aa, aa)

p2 + 2pq + q2 = 1

p2 = AA (Homozygous dominant)

2pq = Aa (Heterozygous)

q2 = aa (Homozygous recessive)

  1. If you are given the genotypes, calculate p and q by adding up the total # of A and a alleles

  2. If you know phenotypes, then use “aa” to find q2, and then q. (p = q-1)

  3. Use p2 + 2pq + q2 to find genotype frequencies

  4. The key to solving H-W problems lies with the homozygous recessive individuals

Minor Causes: 

  • Mutations: Rare, very small changes in allele frequencies

  •  Nonrandom Mating: Affect genotypes, but not allele frequencies

Major Causes: Natural Selection, genetic drift, gene flow

Founder Effect: A few individuals isolated from larger populations 

Bottleneck Effect: Sudden change in the environment drastically reduces population size

3 types of Natural Selection: 

  • Directional Selection 

  • Disruptive (diversifying) Selection 

  • Stabilizing Selection 


Sexual Selection: Form of natural selection - certain individuals more likely to obtain mates 

Sexual Dimorphism: Difference between 2 sexes - size, color, ornamentation, behavior 


Chapter 24: Speciation  


Speciation: Origin of species 

Microevolution: Changes within a single gene pool

Macroevolution: Evolutionary changes that cause one species to turn into 2 different species

Reproductive isolation: barriers that prevent members of 2 species from producing viable, fertile offspring 

  1. Prezygotic Barriers: 

Impede Mating/Fertilization

Ex. Habitat Isolation, Temporal Isolation, Behavioral Isolation, Mechanical Isolation, Gametic Isolation

  1. Postzygotic Barriers: 

Prevent hybrid zygote from developing into viable adult 

Ex. Reduced Hybrid Viability, Reduced Hybrid Fertility, Hybrid Breakdown

Allopatric Speciation: A population forms a new species while geographically isolated from its parent population

Sympatric Speciation: A subset of a population forms a new species without geographic separation

***Polyploidy means instant speciation (for plants)***

Adaptive Radiation: Many new species arise from a common ancestor 

Occurs when: 

  • A few organisms make a way to new, distant areas (allopatric speciation)

  • Environmental Change -> Extinctions -> New Niches for Survivors

Ex. Hawaiian Archipelago 

Hybrid Zones:

  • Incomplete Reproductive Barriers 

  • Possible Outcomes: reinforcement, fusion, stability 


Tempo of Evolution: 

  • Gradualism 

    • Common Ancestor

    • Slow, Constant Change 

  • Punctuated Equilibrium: 

    • Eldridge & Gould 

    • A long period of stasis punctuated by short bursts of significant change 


Chapter 26: Cladistics/Phylogeny

Tools used to determine evolutionary relationships: 

  1. Fossils 

  2. Morphology (homologous structures)

  3. Molecular Evidence (DNA, amino acids)(DNA does not lie)

Phylogenetic Tree: branching diagram that shows the evolutionary history of a group of organisms 

***Nodes show where a common ancestor is between organisms***

Cladogram: Diagram that depicts patterns of shared characteristics among taxa

  • Clade: group of species that includes ancestral species + all descendants

  • Shared derived characteristics are used to construct cladograms 

***Branch lengths can indicate time***

3 Domains: Bateria, Archea, Eukarea 

***Nodes can be rotated***












Chapter 22: Descent with Modification 

  • Relative dating is a method of comparing the ages of two fossils by comparing their placement in rock layers

  • Artificial selection is the selective breeding of plants and animals to produce animals to produce desirable traits in offspring

  • Inheritance of Acquired Characteristics: modifications can be passed on to offspring

  • Natural Selection: the process by which organisms with variation most suited to their environment to survive and leave more offspring 

  • Fitness: How well an organism can survive and reproduce in its environment. 

Evidence for Evolution: 

  1. Direct Observation 

Ex. Insect populations become resistant to pesticides Antibiotic-resistant bacteria 

  1. Fossil Record

  2. Homology: characteristics in related species can have underlying similarities even though functions may differ

Ex. Homologous structures: similar anatomy from common ancestors 

Embryonic homologies: similar early development 

Vestigial Organs: Structures with little to no use

Molecular homologies: similar DNA and amino acid

  1. Biogeography: Geographic distribution of a species 

Ex. Continental drift and Pangaea explain similarities on different continents. 

Convergent evolution: Distantly related species can resemble one another Similar problem, similar solutions

Ex. Torpedo shape of sharks, penguins, and dolphins 

Divergent Evolution: Where you diverge/move away from common ancestors 

Ex. Humans diverging from the monkeys 

Chapter 23: Evolution of Populations

  • Microevolution: change in allele frequencies of a population over generations

  • Evolution is based on genetic variation

  • Point mutations: changes in one base (eg. sickle cell)

  • Chromosomal mutations: delete, duplicate, disrupt, rearrange

  • Sexual recombination: contributes to most of the genetic variation in a population (Crossing over, independent assortment, random fertilization)

  • Population genetics: study of how populations change genetically over time

  • Population: a group of individuals that live in the same area and interbreed, producing fertile offspring

  • Gene pool: all of the alleles for all genes in all the members of a population

  • Fixed allele: all members of a population only have 1 allele for a particular trait

  • Hardy-Weinberg Principle: the allele and genotype frequencies of a population will remain constant from generation to generation

  • Equilibrium + allele and genotype frequencies remain constant

  • CONDITIONS FOR HARDY-WEINBERG EQUILIBRIUM

  1. No mutations

  2. Random mating

  3. No natural selection

  4. Large population size

  5. No gene flow

  • If at least one of these conditions is NOT met, then the population is EVOLVING

  • Allele frequencies: a gene with 2 alleles: p, q

p = frequency of dominant allele (A)

q = frequency of recessive allele (a)

p + q = 1

USE DECIMALS

  • Genotype frequencies: 3 genotypes (AA, Aa, aa)

p2 + 2pq + q2 = 1

p2 = AA (Homozygous dominant)

2pq = Aa (Heterozygous)

q2 = aa (Homozygous recessive)

  1. If you are given the genotypes, calculate p and q by adding up the total # of A and a alleles

  2. If you know phenotypes, then use “aa” to find q2, and then q. (p = q-1)

  3. Use p2 + 2pq + q2 to find genotype frequencies

  4. The key to solving H-W problems lies with the homozygous recessive individuals

Minor Causes: 

  • Mutations: Rare, very small changes in allele frequencies

  •  Nonrandom Mating: Affect genotypes, but not allele frequencies

Major Causes: Natural Selection, genetic drift, gene flow

Founder Effect: A few individuals isolated from larger populations 

Bottleneck Effect: Sudden change in the environment drastically reduces population size

3 types of Natural Selection: 

  • Directional Selection 

  • Disruptive (diversifying) Selection 

  • Stabilizing Selection 

Sexual Selection: Form of natural selection - certain individuals more likely to obtain mates 

Sexual Dimorphism: Difference between 2 sexes - size, color, ornamentation, behavior 

Chapter 24: Speciation  

Speciation: Origin of species 

Microevolution: Changes within a single gene pool

Macroevolution: Evolutionary changes that cause one species to turn into 2 different species

Reproductive isolation: barriers that prevent members of 2 species from producing viable, fertile offspring 

  1. Prezygotic Barriers: 

Impede Mating/Fertilization

Ex. Habitat Isolation, Temporal Isolation, Behavioral Isolation, Mechanical Isolation, Gametic Isolation

  1. Postzygotic Barriers: 

Prevent hybrid zygote from developing into viable adult 

Ex. Reduced Hybrid Viability, Reduced Hybrid Fertility, Hybrid Breakdown

Allopatric Speciation: A population forms a new species while geographically isolated from its parent population

Sympatric Speciation: A subset of a population forms a new species without geographic separation

***Polyploidy means instant speciation (for plants)***

Adaptive Radiation: Many new species arise from a common ancestor 

Occurs when: 

  • A few organisms make a way to new, distant areas (allopatric speciation)

  • Environmental Change -> Extinctions -> New Niches for Survivors

Ex. Hawaiian Archipelago 

Hybrid Zones:

  • Incomplete Reproductive Barriers 

  • Possible Outcomes: reinforcement, fusion, stability 

Tempo of Evolution: 

  • Gradualism 

    • Common Ancestor

    • Slow, Constant Change 

  • Punctuated Equilibrium: 

    • Eldridge & Gould 

    • A long period of stasis punctuated by short bursts of significant change 

Chapter 26: Cladistics/Phylogeny

Tools used to determine evolutionary relationships: 

  1. Fossils 

  2. Morphology (homologous structures)

  3. Molecular Evidence (DNA, amino acids)(DNA does not lie)

Phylogenetic Tree: branching diagram that shows the evolutionary history of a group of organisms 

***Nodes show where a common ancestor is between organisms***

Cladogram: Diagram that depicts patterns of shared characteristics among taxa

  • Clade: group of species that includes ancestral species + all descendants

  • Shared derived characteristics are used to construct cladograms 

***Branch lengths can indicate time***

3 Domains: Bateria, Archea, Eukarea 

***Nodes can be rotated***