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Biology > chapter twenty-three/twenty-four > Flashcards

chapter twenty-three/twenty-four Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

3 major factors that alter allele frequency

A
  1. natural selection
  2. genetic drift
  3. gene flow
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2
Q

genetic drift

A
  • allele frequencies fluctuate unpredictably/randomly from one gen to next
  • reduces genetic variation
  • sig in small populations
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3
Q

gene flow

A
  • movement of alleles among populations
  • transferred through fertile ind. or gametes
  • reduces variation
  • decrease/increase fitness
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4
Q

founder effect

A

few individuals become isolated from larger population
- allele frequencies can be dif

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5
Q

bottleneck effect

A

sever drop in pop size due to environmental change
- can be affect by genetic drift

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6
Q

what does evolution by natural selection involve?

A

change and sorting
- new genetic variations arise by chance
- beneficial alleles sorted

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7
Q

what results in adaptive evolution?

A

natural selection
- increases frequencies of alleles that provide reproductive advantage
- acts on organism’s phenotype

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8
Q

why are the phrases “struggle for existence” and “survival of the fittest” misleading?

A
  • imply direct competition
  • reproductive success more subtle
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9
Q

relative fitness

A

contribution an ind makes to the gene pool of the next generation relative to contributions of other ind

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10
Q

3 modes of selection

A
  1. directional
  2. disruptive
  3. stabilizing
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11
Q

directional selection

A

favors one extreme end of phenotypic range

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12
Q

disruptive selection

A

favors individuals at both ends of phenotypic range

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13
Q

stabilizing selection

A

favors intermediate variants and acts against extreme phenotypes

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14
Q

what increases the frequencies of alleles that enhance survival and reproduction?

A

natural selection

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15
Q

what occurs as the match between an organism and its environment

A

adaptive evolution

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16
Q

why is adaptive evolution a continuous process?

A

the environment can change

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17
Q

why don’t genetic drift and gene flow lead to adaptive evolution

A

they can increase/decrease match between organism and its environment

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18
Q

sexual selection

A

natural selection for mating success

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19
Q

sexual dimorphism

A

marked differences between the sexes in secondary sexual characteristics

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20
Q

intrasexual selection

A

competition among ind of one sex (often males) for mates of opposite sex

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21
Q

intersexual selection

A
  • mate choice
  • occurs when ind of one sex (usually females) are choosing in selecting mates
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22
Q

how to female preferences evolve?

A

good genes hypothesis - if trait is related to male health, both male trait and female preference for trait should increase in frequency

23
Q

neutral variation

A

genetic variation that doesn’t confer a selective advantage/disadvantage

24
Q

diploidy

A

maintains genetic variation in form of recessive alleles
- heterozygotes can carry recessive alleles that are hidden from effects of selection

25
Q

balancing selection

A

occurs when natural selection maintains stable frequencies of 2+ phenotypic forms in a pop
- includes heterozygote advantage and frequency-dependent selection

26
Q

heterozygote advantage

A

occurs when heterozygous have greater fitness than homozygotes
- natural selection will maintain 2 alleles at that locus
- sickle-cell allele causes mutations in hemoglobin but also confers malaria resistance

27
Q

frequency-dependent selection

A

fitness of phenotype declines if it becomes to common in pop
- selection can favor less common phenotype in pop
- equal numbers of right and left mouth fish

28
Q

why can natural selection not fashion perfect organisms?

A
  • can only act on existing variations
  • evolution limited by historical constraints
  • adaptations often compromises
  • chance, natural selection, and environment interact
29
Q

what preserves genetic variation?

A

diploidy and balancing selection

30
Q

speciation

A

origin of new species

31
Q

microevolution

A

changes in allele frequency in pop over time

32
Q

macroevolution

A

broad patterns of evolutionary change above species level

33
Q

“species” word

A

Latin word meaning “kind” or “appearance”

34
Q

what is compared when grouping organisms?

A

morphology, physiology, biochemistry, DNA sequences

35
Q

biological species concept

A
  • states species is a group of populations whose members have the potential to interbreed and produce viable/fertile offspring and don’t breed successfully w/ other populations
36
Q

what holds the phenotype of a population together?

A

gene flow between populations

37
Q

reproductive isolation

A

existence of biological factors/barriers that impeded 2 species from producing viable/fertile offspring
- prezygotic and postzygotic

38
Q

hybrids

A

offspring of crosses between dif species

39
Q

prezygotic barriers

A

block fertilization from occurring by:
1. impeding dif species from attempting to mate
2. preventing successfully completion of mating
3. hindering fertilization if mating is successful

40
Q

types of prezygotic barriers

A
  1. habitat
  2. temporal
  3. behavioral
  4. mechanical
  5. gametic
41
Q

habitat isolation

A

2 species encounter each other rarely/not at all because they occupy dif habitats

42
Q

temporal isolation

A

species that breed at dif times of day, dif seasons, or dif years can’t mix gametes

43
Q

behavioral isolation

A

courtship rituals and other behaviors unique to species are effective barriers

44
Q

mechanical isolation

A

morphological dif can prevent mating

45
Q

gametic isolation

A

sperm of one species may not be able to fertilize eggs of another species

46
Q

post zygotic barriers

A

prevent hybrid zygote from developing into a viable, fertile adult
1. reduced hybrid viability
2. reduced hybrid fertility
3. hybrid breakdown

47
Q

reduced hybrid viability

A

genes of different parent species may interact and impair hybrid’s development and survival

48
Q

reduced hybrid fertility

A

even if hybrids are vigorous, they may be sterile

49
Q

hybrid breakdown

A

some first-get hybrids fertile, but when they mate w/ another hybrid or w/ either parent species, offspring of next gen are feeble/sterile

50
Q

limitations of biological species concept

A
  1. can’t be applied to fossils/asexual organisms/prokaryotes
  2. emphasizes absence of gene flow
51
Q

can gene flow occur between distinct species?

A

yes, like grizzly and polar bears

52
Q

morphological species concept

A

species defined by body shape and structural features
- applies to sexual/asexual species but relies on subjective criteria

53
Q

ecological species concept

A

views species in terms of its ecological niche
- applies to sexual/asexual, emphasizes role of disruptive selection

54
Q

phylogenetic species concept

A

defines species as smallest group of ind on phylogenetic tree
- applies to sexual/asexual, but difficult to determine degree of difference required for separate species

Biology (35 decks)

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