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24 Cards in this Set
- Front
- Back
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Natural Selection
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Individuals vary in characteristics that are heritable. In a particular environment, certain versions of these traits help individuals survive better & reproduce more than other versions. These traits are disproportionately passed on and become more common over time.
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Darwin's 4 postulates
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1. Variation
2. Heritability 3. Differential Reproduction 4. Nonrandom Reproduction |
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Fitness
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ability to successfully reproduce relative to your population.
(typically measured as # offspring) |
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Adaptation
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change in species to increase its fitness.
a trait that increases fitness. |
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Evolution
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change in allele frequencies over time.
-species are related by common ancestry. |
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Genetic Drift
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random fluctuation in allele frequency over time, due to chance alone without any influence by natural selection (small populations).
-NO nonrandom reproduction (aka random reproduction) |
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Directional selection
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favors individuals at one extreme of the phenotype in a population.
Example: Drought in Galapagos increase the avg size & hardness of the seeds available, causing small bird to have difficulty finding food, and so the large birds survived best. |
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Stabilizing selection
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selection favoring the middle in the distribution of phenotypes
Example: In humans, infant mortality and birth rate. Highest mortality at 2 and 11 lbs, lowest at 7 lbs. |
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Disruptive selection
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two extreme phenotypes in the population leaves more offspring than intermediate phenotype, which has lower fitness.
Example: Black-bellied Seedcracker, a type of bird that feeds on 2 species of sedge, similar in size but very different in hardness. |
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How can natural selection maintain variation?
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(1) Disruptive selection
(2) Heterozygous advantage (3) Negative frequency dependent selection (FDS) (4) Multiple-niche polymorphism |
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Sexual Selection
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selection caused by differences in mating success and fertilization success.
(1) Male-male competition (2) Mate choice |
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Types of male-male competition
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(1) Direct fighting
(2) Better/faster at finding females (3) Better at fertilizing eggs |
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Hypotheses of mate choice
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1. Good genes
2. Good parent/ provider 3. Sexy sons 4. Sensory exploitation |
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Types of ornaments
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1. Handicap to survival
-only males w/ good genes can afford the handicap 2. Indices (correlates to health) In both cases, males honestly advertise their genetic quality |
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Sexual conflict
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one sex manipulates the other in ways that benefit its own reproduction success but reduces success of its mates
(1) Harassment (2) Forced copulation (3) Chemical manipulation (4) sexual cannibalism (of males) (5) sexual deception |
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Optimal Foraging Theory
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(1) animals choose among alternate behaviors.
(2) pick strategies that maximize fitness |
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Biological sex
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fertilization of haploid (1n) gametes to form diploid (2n) zygotes
Key features: (1) meiosis (2) recombination (3) fertilization |
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anisogamy
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different size and structure of gametes (sperm vs egg)
Hint: an-iso-gamy an= not iso=same gamy=gamete |
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hermaphrodites
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both genders in the same individual
(1) simultaneous (2) sequential |
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Costs and benefits of sex
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Costs
(1) Effort of finding, courting, mating (mortality, time, material, energy) (2) Maintaining the complex machinery of meiosis (3) Only 1/2 of genes per offspring that are transferred to next generation Benefits (1) Diversity in offspring (in changing environments) (2) Sex shuffles genotypes a. important in unpredictable environments b. can create new, better gene combinations c. can create new bad gene combos-> selectively remove ("weed out" really bad genes) THEREFORE, expect sex when benefits of diversity in offspring outweigh costs of sex |
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senescence
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increase mortality & decline in fecundity & physiological function as we age
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Theories on senescence
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1. Disposable-soma
- body is expendable, but germ line must go on - trade-off between repairing/maintaining gamete DNA vs somatic DNA (gamete wins) - energy that goes into reproduction doesn't cease as you grow old 2. Antagonistic Pleiotropy - same genes that are beneficial early in life are deleterious later in life 3. Mutation-accumulation - the older we are, the more mutations we get - molecular damage fails to be repaired |
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R & K Selection
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different life-history categories based on habitat use & competition
-r selected species specialize in disturbed environments w/ out much competition. -k is better w/ more intense competition |
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Fecundity
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-Potential ability to produce eggs or young
-Also the rate of production of young by a female |
