ZOO 101 Evolution Flashcards

Evolution

pop genotype changes over gens

Evolution Misconception

individuals !evolve; natural selection acts on individuals -> pops evolve over gens

Evolution (Darwin)

descent w/ modification

Microevolution

pop allele freq changes over gens

Genotype

genetic composition

Phenotype

physical traits; genotype & env

Genetic Variation

individual genotype diffs; evolutionary req

Phenotypic Variation

individual phenotype diffs

Genetic Variation Mechanism (Either-Or)

allele -> phenotype

Genetic Variation Mechanism (Continuum)

2+ genes -> phenotype

Genetic Variation Causes

mutation, gene duplication, sexual reproduction

Sexual Reproduction Variation Mechanisms

crossing over, independent assortment, fertilization

Genetic Variation Measures

gene/nucleotide variability

Gene Variability

avg % heterozygous genes

Nucleotide Variability

nucleotide base variations

Nucleotide Variability Impact

> noncoding segment freq -> < phenotype variation

Mutation

nucleotide sequence change

Mutation Types

point mutation, chromosomal changes, gene duplications

Small Gene Duplications

harmless -> persist & mutate -> > genome w/ new functions

Mutation Causes

DNA replication errors, UV/radiation/chemical exposure

Mutation Rates

eukaryote/prokaryote > gene/gen freq

Point Mutation

base change

Chromosomal Changes

chromosome part deletion/translocation

Translocation

chromosome part -> diff chromosome

Heterozygote Protection

dominant allele masks - recessive allele; diploids

Neutral Variation

mutation !-> new adv/dis

Neutral Variation Causes

noncoding/somatic mutation, genetic code redundancy

Allele Frequency Factors

natural selection, genetic drift, gene flow

Natural Selection

favors heritable phenotype w/ > reproduction

Genetic Drift

chance events altering allele freq; - correlated w/ pop size

Gene Flow

allele transfer btwn pops

Gene Flow Impacts

can prevent local adaptation / spread + alleles across pops

Population

species w/ reproductive compatibility in same area

Gene Pool

every allele type in pop

Fixed Allele

only 1 allele for specific pop locus; all homozygous

Hardy-Weinberg Equation

p^2 + q^2 (homozygote) + 2pq (heterozygote) = 1

Hardy-Weinberg Equilibrium

const allele/genotype freq ot

Hardy-Weinberg Req 1

!mutations; const gene pool

Hardy-Weinberg Req 2

rand mating (gamete mixing) -> const genotype freq

Hardy-Weinberg Req 3

!natural selection -> const allele freq

Hardy-Weinberg Req 4

large population -> < genetic drift

Hardy-Weinberg Req 5

!gene flow -> const allele freq

Adaptive Evolution

trait freq + survival/reproduction

trait freq + survival/reproduction > ot

Adaptive Evolution Cause

natural selection only consistent mechanism

Founder Effect

subpop isolated -> new pop w/ diff gene pool

Bottleneck Effect

pop size < -> allele freq change & genetic drift until regrowth

Genetic Drift

rand allele freq changes, < genetic variation, const - alleles

Relative Fitness

individual's relative contribution to next gen's gene pool

Natural Selection Types

directional, disruptive, stabilizing

Directional Selection

> 1 phenotypic extreme; env change

Disruptive Selection

> both phenotypic extremes

Stabilizing Selection

disfavors phenotypic extremes & favors intermediate variants -> < variation

Sexual Selection

certain heritable traits -> > reproduction

Sexual Dimorphism

secondary sexual characteristics diffs within species

Types of Sexual Selection

intrasexual & intersexual

Intrasexual Selection

1 sex (often males) compete for mates

Intersexual Selection

1 sex (often females) carefully selects mates

"Good Genes" Hypothesis

females prefer male traits correlated w/ overall genetic quality/health

Balancing Selection

natural selection maintains 2+ phenotypic forms in pop

Balancing Selection Types

frequency-dependent, heterozygote advantage

Frequency-Dependent Selection

phenotype fitness depends on pop freq (often favors least common)

Heterozygote Advantage

heterozygous locus -> > fitness

Heterozygote Advantage Example

sickle-cell trait -> protects against malaria -> maintains - recessive allele

Evolution Constraint 1

natural selection only acts on existing variations

Evolution Constraint 2

historical constraints limit evolution

Evolution Constraint 3

adaptations have trade-offs

Evolution Constraint 4

chance/natural selection/env interact

Speciation

1 species -> 2

Macroevolution

broad species-level evolution pattern

Biological Species Concept

reproductive compatibility only within pop group

Biological Species Concept Limitations

!apply to fossils, asexual organisms, distinct species w/ gene flow

Reproductive Compatibility

can produce fertile offspring

Reproductive Isolation

prevents interspecies reproductive compatibility

Hybrids

interspecies offspring

Reproductive Isolation Types

prezygotic/postzygotic barriers

Prezygotic Barriers

prevent fertilization

Prezygotic Barrier Types

habitat/temporal/behavioral/mechanical/gametic isolation

Habitat Isolation

minimal inter-habitat interaction between species

Temporal Isolation

species w/ diff breeding times can't mix gametes

Behavioral Isolation

species unique behavior/courtship - interspecies mating

Mechanical Isolation

morphological diffs prevent mating completion

Gametic Isolation

prevents fertilization

Postzygotic Barrier Types

reduced hybrid viability/fertility, hybrid breakdown

Reduced Hybrid Viability

gene interactions - hybrid survival/development

Reduced Hybrid Fertility

diff chromosome #/structure -> sterility

Hybrid Breakdown

hybrid offspring fertility <

Morphological Species Concept

structural features distinguish species

Ecological Species Concept

ecological niche distinguishes species

Allopatric Speciation

geographic isolation -> interrupted gene flow -> speciation

Sympatric Speciation

speciation in same area

Sympatric Speciation Causes

polyploidy, sexual selection, habitat differentiation

Polyploidy

+X chromosomes during cell division -> speciation; 80% of plants

Autopolyploid

2+ chromosome sets from same species

Allopolyploid

hybrids asexually reproduce over gens -> polyploid fertile only w/ hybrids

Habitat Differentiation

subpop exploits new habitat/resource -> reproductive isolation -> sympatric speciation

Hybrid Zone

region < reproductive barriers -> > hybrid offspring

Hybrid Zone Outcomes

reinforcement, fusion, stability

Reinforcement

natural selection -> > prezygotic barriers

Fusion Mechanism

> gene flow -> < reproductive isolation -> hybridizing species fuse

Stability

continued hybrid formation; caused by > hybrid fitness / continued parent pop migration into zone