Chapter 20 Flashcards

Question

Water Striders

Answer 1

Large female water striders lay more eggs per day than small but survive for shorter periods of time. Intermediate sized females produce the most offspring over the course of their lives and thus have the highest fitness

Answer 2

Females evaluate a male's quality and then decide whether to mate Most males only mate, don't carry eggs, try to mate with as many females as possible

Answer 3

The energy and time each sex invests in producing and rearing offspring Females have a higher parental investment (typically) Male Mormon crickets exceed normal by transferring a protein-containing packet to females during mating.

Answer 4

Intrasexual selection - competitive interactions between members of one sex. Some males won't mate, others a lot Intersexual selection - Mate choice Secondary sexual characteristics - antlers and horns used to combat other males, long tail feathers and bright plumage used to persuade opposite sex. Sexual dimorphism - Differences between sexes (male larger than female, color) Sperm competition - selects for features that increase probability that a male's sperm will fertilize the egg

Answer 5

Direct - Female benefit by choosing the male that can provide the best care. Males can provide territory for food and refuge. Indirect - Higher-quality offspring. Choose the male that is healthiest or oldest. HANDICAP hypothesis - only genetically superior mates survive with a handicap such as a long tail that is a hinderance in flying

Answer 6

Evolution in males of a signal that exploits preexisting biases. Females respond to certain stimuli. Tungara frog, finches with feathers glued to head

Answer 7

Fitness of a phenotype depends on its frequency within the pop. Negative freq- Rare phenotypes favored by selection, rare forms may not be in "search image" of predators, preyed upon less frequently. Water boatman - fish eat the most common color by more than chance alone Positive freq- Favors common form, tends to eliminate variation, oddballs stand out and are picked off. ex. School of fish

Answer 8

Selection favors one phenotype at one time and another phenotype at another time. Effect will be to maintain genetic variation in the pop. over time. Medium ground finch of Galapagos, birds with big bills favored during drought, small bills favored during wet conditions

Answer 9

Heterozygotes are favored over homozygotes. Works to maintain both alleles in pop. Sickle cell anemia

Answer 10

Many traits affected by more than one gene. Selection operates on all the genes for the trait. Changes the pop. depending on which genotypes are favored. Types - Disruptive, Directional, Stabilizing: and could oscillate

Answer 11

Acts to eliminate intermediate types. Two peaks form for ex. "large and small" not intermediate Different beak size of African black-bellied seedcracker finch. Large beaks for big seeds, small beak for small seed. Intermediate sized beak is too clumsy for small seed not big enough for large seed

Answer 12

Acts to eliminate one extreme. Ex. Fast over slow, or small over big. Often occurs in nature when the environment changes. In Drosophila, eliminated flies that moved toward the light, fewer in pop. over generations. New generations avoid light

Answer 13

Acts to eliminate both extremes, makes intermediate more common by eliminating extremes. Humans, infants with intermediate weight at birth have highest survival rate.

Answer 14

Above waterfall killifish rarely eat guppies, become larger more flashy Bellow waterfall pike cichlid eat guppies, stay small, reproduce earlier, stay dull

Answer 15

Constructive - spread beneficial mutation to other populations Constraining - Can impede adaptation by continual flow of inferior alleles from other populations

Answer 16

Eyes on insect, not genetic environment, not evolution Thoroughbred horses speed