Biol322 FInal

Hardy-Weinberg Equilibrium

Null model for population genetics, compare data to see how evolution might operate

Hardy-Weinberg Equilibrium Conditions

Large population size

No natural selection

No migration

No mutations

Random mating

Quantitative Traits

Continuous variation (ex. height)

Polygenic Traits

Controlled by many genes

Modes of Selection

Directional

Stabilizing

Disruptive

Biological Species Concept

Pros/Cons

Species are reproductively isolated from one another

Pros: based on actual biological processes

Cons: doesn’t work for fossils or asexual organisms

Morphological Species Concept

Pros/Cons

Species are groups that are physically similar

Pros: easy

Cons: can miss cryptic species

Phylogenetic Species Concept
Pros/Cons

Species are the smallest monophyletic group with shared derived traits

Pros: precise

Cons: requires a lot of data

Three Species Concepts

Biological species concept

Morphological species concept

Phylogenetic species concept

Evolutionarily Independent Lineages

Species are lineages evolving separately over time; ties all species concepts together

Cryptic Species

Morphologically similar lineages that are genetically different

Steps of Speciation

1. Isolation of populations

2. Divergence

3. Reproductive isolation

Mechanisms for Evolutionary Isolation

Allopatric model

Sympatric model

Allopatric Model

Geographic isolation

Disperal

Individuals move to a new area

Vicariance

Physical barrier splits a population

Sympatric Model

Speciation without geographic separation (ex. niche)

Polyploidy

An organism has more than two sets of chromosomes

Mechanisms of Divergence

Genetic drift

Natural selection

Sexual selection

Factors of Reproductive Isolation

Behavioral (ex. mating signals)

Temporal (ex. breeding times)

Mechanical (ex. incompatible structures)

Genetic incompatibility

Hybridization

Interbreeding of species

Adaptive Radiation

One species → many species with niches

Parthenogenesis

Offspring from unfertilized egg

Cost of Sexual Reproduction

Slower

Breaks up good gene combinations

Time/energy to find mates

Risk of disease

Pass on 50% of genes

Sex Evolved…

DNA repair hypothesis (repairs damaged DNA)

Parasitic DNA hypothesis (spreads genetic elements)

Sex Maintained…

Mullers ratchet (removes bad mutation)

Red queen hypothesis (variation fights parasites)

Linkage Equilibrium

Genes inherited independently

Benefits of Sexual Reproduction

Genetic diversity

New allele combinations

Helps populations adapt

Hermaphrodites

An organism that produces both small and large gametes

Sexual Dimorphism

Male and female are visually distinct

Intrasexual Selection

Same sex competing for mates

Intersexual Selection

One sex (usually female) chooses mates

Sperm Competition

Multiple males’ sperm compete to fertilize a females eggs

Cryptic Female Choice

Female influence which sperm fertilizes eggs after mating

Good gene Hypothesis

Choose mates with desirable traits

Sexy Son Hypothesis

Choose mates whose offspring will be attractive

Handicap Principle

Costly trait = very fit

Runaway Sexual Selection

Extreme traits

Copulatory Courtship

Behavior during mating that influences fertilization

Kin Selection

Helping relatives, increases inclusive fitness

Relatedness of Relatives

Siblings r = 0.5

Half-sibling r = 0.25

Cousins r = 0.125

Eusociality

High social organization

Overlapping generations

Cooperative brood care

Reproductive division of labor

Males (haploid/diploid)

Haploid

Females (haploid/diploid)

Diploid

Social Inclusionary Traits

Traits that allow individuals to join social groups

Mutualism

Relationship where both species/organisms benefit

Character Displacement

Species become more different when living together

Cospeciation

Two species speciate together (ex. host and parasite)

My Organism

King Penguin

Aptenodytes patagonicus