OSU Biology 1114 - Midterm 2

Coevolution

The joint evolution of 2+ interacting species. Pressure from each species acts as selective agent for other.

Asexual Reproduction

Formation of offspring without fusion of egg and sperm. Offspring genetically identical to parent.

Sexual Reproduction

Formation of offspring by fusion of male and female gametes. Offspring inherit traits from both parents.

Evolution will NOT occur if:

1. Mating is random

2. No natural selection

3. No mutation

4. No migration

Budding

Offspring develops as outgrowth of parent

Fission

Parent splits into two organisms of about equal size.

Root Suckering

Many clonal inds. sprout from roots of single ind.

Parthenogenosis

Unfertilized eggs develop into offspring. Sex changing species - hormonal production shifts.

Frequency Dependent Selection

The fitness of a phenotype that depends on how common it is in a population. Ex: side-mouthed scale eating fish

Advantages of Sex ;)

- Variation (allows selection)

- Fewer deleterious alleles (asexual = keep being passed on, die out faster)

Mutation Meltdown

The increasing proportion of low fitness individuals with many deleterious alleles in asexual populations. Explains greater extinction rates in asexual species.

Sexual Selection

Individuals with certain inherited traits are more likely to attract mates than others. Form of Nat. Selection.

Reproductive Differences between Males and Females

Females:

- Limited # of gametes + increased time consumption

- More selective (quality)

Males:

- Excess gametes + no gestation period

- Not selective (quantity)

Operational Sex Ratio (OSR)

The ratio of males in a population ready to mate with females in pop that are ready to mate. Skewed due to reproductive differences.

Contributions to Offspring

Female:

- Often provide parental care

- Greater energetic cost (gestation, rearing)

Males:

- Often hit it and quit it

- Lower energetic cost

Differential Parental Investment (PI)

Measured as each parent's contribution to rearing offspring. Female gametes, limited = high PI. Male gametes = unlimited = low PI.

Female Reproductive Strategy

Find mate with good genes or resources so offspring have better chance of survival.

Male Reproductive Strategy

Mate with as many partners as possible, leave rearing to females.

Variable Reproductive Success

Female: Relatively Uniform

- Not limited by mating opportunities

- Gametes able to be used more often

- Limited by resources

Male Reproductive Success: Variable

- Limited by mating opportunities

- Must demonstrate desirable qualities

Average Reproductive Success

SAME FOR BOTH SEXES

Intrasexual Selection

Results from competition between members of one sex for mating opportunities (access to or resources needed). Usually male-male. (Elephant seals)

Cuckoldry

Indirect male-male competition. Males unwittingly invest parental care into unrelated offspring.

Cuckoldry - Sneaker Males

Tiny males are undetected by alphas and "free-ride" off of mating opportunities (fish wait for spawning and sneak attack with sperm).

Cuckoldry - Satellites

Too big to be sneakers, look like females so are tolerated by alphas, mate anyway.

Cuckoldry - Sperm Competition

Removing another male's sperm - barbed and curved penis.

Intersexual Selection

One sex prefers members of other sex with a certain phenotype. Usually females choosing males.

Cues for Female Choice

1. Features suggesting health/feeding capability

2. Features emphasizing distinction b/w sexes (no wasted effort on androgyny)

Sexual Dimorphism

Difference in appearance of females and males within same species.

Zahavi's Handicap Hypothesis

Individuals with well developed sexually selected characteristics have survived some sort of test. Explains extreme morphologies. Individuals that survive DESPITE the "handicap" must have a superior genotype. Honest indicator of fitness.

Correlation Coefficient (r)

Indicates direction and strength of a linear relationship b/w 2 variables. Strong is closest to 1 or -1. >0 = Positive relationship. <0 = Negative relationship.

R^2

Proportion of variation in dependant variable that is explained by variation in independent variable. Always positive, squared number + no directional value.

Altruism

An action reducing an individual's direct fitness while increasing fitness of another.

Nash Equilibrium

The strategy that is the best response given other player's response.

Prisoner's Dilemma

Confess (cooperate) or remain silent (defect), not knowing other player's decision. Selfishness is the best strategy.

Evolutionarily Stable Strategy (ESS)

The selfish strategy. A strategy that, if established, can't be invaded by something using an alt. strategy. Suggests cooperative phenotypes will be selected against.

Cooperative Breeding

Some individuals don't reproduce (lose direct fitness) and rear relatives (often siblings, indirect fitness). Non-altruistic, actually selfish.

Indirect Fitness

Fitness gained by allele transmission by helping relative offspring.

Inclusive Fitness

Fitness gained through both direct and indirect methods. Inclusive fitness = direct + indirect fitness

Kin Selection

Evol. strategy in which organisms don't reproduce (lose direct fitness) to benefit a relative's reproductive success (indirect fitness). Ultimately increases total fitness of helper (selfish).

Relatedness (r)

Probability that two individuals share given allele. Used to predict if altruistic behaviors will occur. Between siblings/half-siblings (paternal or maternal), grandparents, nieces/nephews, r = .25, First cousins, r = .125.

Hamilton's Rule

Individuals should behave altruistically IF fitness gain > fitness lost from not reproducing.

Act Altruistically If:

Cost < indirect fitness gains (relatedness x benefit to relative's fitness)

Act Selfishly If:

Cost > indirect fitness gains (relatedness x benefit to relative's fitness)

Extra-pair Copulations

Females mating with males other than partner (maternity certain, paternity uncertain).

Reciprocal Altruism

Altruism b/w non-kin. Individuals interact multiple times and change individual interactions based on past behaviors. Tit for tat. Can punish selfishness by not helping in future. Ex: Vampire bats.

Genetic Drift

A RANDOM change in allele frequencies from gen to gen. Ex: volcano eruption, ant hill being stepped on. Less likely in large populations. Reduces genetic diversity - allele fixation.

Heterozygosity (H)

The probability of drawing 2 DIFFERENT alleles from the gene pool of a population. H = 1 - (p^2 + q^2)

Fragmentation

Previously large. continuous habitat broken into smaller, unconnected pores.

Founder Event

A new, smaller population of founders break off from original population. No representation lost.

Founder Effect

Occurs IF new population found has lower genetic diversity than original population.

Bottleneck Effects

Occurs when an environmental/human catastrophe decimates a large percent of population. Size may rebound, but diversity won't. Causes loss of genetic diversity.

Gene Flow

Introduction or removal of alleles from a population - changes allele frequencies.

Mutation

A permanent, RANDOM change in DNA sequence of an organism.

Genetic Polymorphism

Having multiple different alleles for a gene. Mutation increases. A function of the rate of drift and mutations.

Microevolution

Changes within a population over generation (single species).

Macroevolution

Evolutionary changes resulting in a different species (speciation).

Evolution and Species Formation

Ancestral Population --> Isolated into groups (no longer interbreed) --> Each acquires mutations INDEPENDENTLY in diff environments --> Become so differentiated that they no longer mate. Extant species can't evolve from one another, have common ancestors.

Phylogenetics

Studies evolutionary history/relatedness of groups.

Phylogeny

A hypothesis of evolutionary relationships between groups of shared characteristics, connected to a single ancestral species (outgroup - from which others diverge from).

Nodes

Common ancestors. Where species diverge from a common ancestor.

Homology

A similarity resulting from common ancestry. Ex: Mammalian forelimb.

Plesiomorphy

Character states found in the outgroup. Traits that are diverged from.

Apomorphy

Derived character states found in descendants of group. Acquired AFTER divergence.

Synapomorphy

Shared, derived character states that indicate homology (similar trait to ancestor group)

Phylogeny - Polarity

0 = ancestral state, 1 = derived state

Monophyletic Group

Clade. A common ancestor and all of its descendants. Only valid evolutionary group.

Evolutionarily Invalid Groups - Paraphyletic

A group containing a common ancestor but NOT all of its descendants. Ex: reptiles

Evolutionarily Invalid Groups - Polyphyletic

Group characterized by 1+ homoplasies (character states appear in 2 taxa but NOT evolved from same ancestor).

Homoplasy

Result of convergent evolution. Character states appear in same 2 taxa but NOT evolved from a common ancestor. Exposed to similar selection.

Convergent Evolution

Independent evolution of the same character state in multiple, separate lineages.

Parsimony

The simplest explanation. The best tree is the one with the fewest evol. steps.

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