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Biology 191 Lect. 4
Biology 191 Lect. 4 - Biology 191 Lecture 4, Exam 1 Study
| Question | Answer |
|---|---|
| 3 types of natural selection | directional, disruptive, stabilizing |
| Directional Selection | one extreme phenotpe if the fittest (colonization of sandy islands by dark deer mice) |
| Disruptive Selection | phenotypes at both ends of the range are fitter than the intermediates between them (beak length of black-bellied seed crackers (short beaks for soft seeds, long beaks for hard seeds) |
| Stabilizing Selection | the average phenotype if the fittest (most common form of selection) (ex. birth weight - larger babies are stronger and healthier, but babies too large risk birth complications) |
| Heterozygote advantage | When greater firness of heterzygote maintains two or more alleles at locus (ex. sickle cell allele maintained by malaria resistance) |
| Varying selection (time & space) | temporarily oscillating selection favors one phenotype at one time, another phenotype at another time <br /> space - favor one phenotype in one environ, another in another environ |
| negative frequency dependent selection | the fitness of a phenotype depends on its frequency within the population (negative = rare phenotype is favored -> only negative freqency-dependent selection maintains variation) |
| Sexual selection: | definition: differential reproductive success resulting from competition between members of one sex, usually males to achieve matings and/or fertilizations <br /> can result in evolution of traits detrimental to survival |
| Intrasexual competition | male-male competition (evolution of weapons or intimidating signals of strength) |
| intersexual mate choice | - usually female choice <br />- evolution of sexually atractive traits and courtship behavior |
| Sexually selected traits: weapons versus ornaments | weapons: larger size of males, antlers in deer stags, tusks of bull elephants < br />ornaments - peacock's tale, dewlap in male lizards, elaborate plumage adn courtship in cock-of-the-rock, stalked eyes of some flies |
| Sexual dimorphism: why typically greater in polygynous species? | Sexual Dimorphism- marked difference between sexes in secondary sexual characteristics. <br /><br /> Greater in polygynous because (1) single male mates w many females (2) genreates more intense sex selection (eleph. seals) |
| Why are males more often the target of sexual selection? | they produce small, numerous physiologically inexpexpensive sperm vs females who produce numerous small, physiologically expensive eggs |
| harem polygyny | type of male-male competition where the males guard the females directly (elephant seals, horses, deer) |
| resource defense polygyny | male-male competition where the male guards a resource important to females (ex. the cortez damselfish) |
| Lek mating | where the males gather to display to females |
| Experiment demonstrating female choice in widowbirds | Question: did sexual sel. affect the evolution of long tails in african long-tailed widowbirds? <br />A: Yes, they artificially lengthened and shortened their tails, and the nests increased and decreased for males dependant on their tail length |
| Costs and potential benefits of female choice | costs: - time and energy devoted to mate searching - male harassment <br /> benefits - material benefits (gifts, territory quality) - genetic benefits (good genes) |
| What is sensory exploitation hypothesis and what evidence supports it? | That males exploit pre-existing biases in the female's sensory system to increase their attractiveness ex. (euglossine bees where males produce pheromone that smells like an orchid) |
| Waist-to-hip ratio (WHR): sexual dimorphism; male preference for low WHR and why? | prefer .6 to .8, whr because <br /> (1) narrow waist and large breast exhibits hormonal profiles indicitavie of high conception probability <br /> (2) indicates non-pregnancy |
| Female facial attractiveness: what and why? | - fuller lips, narrow chin, high cheek bones and large eyes <br /> - evidence that these traits indicate higher levels of pubertal estrogens and lower levels of androgen exposure |
| Male facial attractiveness: what and why? | women prefer more masculinized faces for short term mate (stm) than LTM. prefer more masculinized STM during ovulation. <br />- masculine features correlated w testosterone levels in puberty (test. is poweful immunosuppressant), masculine face = health |
| Male facial attractiveness: what and why? (2) | strong correlation between male interest and female assesment of interest based on facial characteristics |
Created by:
analeah
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