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Zoology > Chapter 19 > Flashcards

Chapter 19 Flashcards

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1
Q

what is a gene?

A

a segment of DNA that codes for a phenotype

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2
Q

what is an allele?

A

different versions of a particular gene

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3
Q

what is a genotype?

A

the 2 alleles that define a phenotype

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4
Q

what is a phenotype?

A

physical representation of a genotype

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5
Q

what does homozygous mean?

A

alleles for a genotype are the same

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6
Q

what does heterozygous mean?

A

alleles for a genotype are different

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7
Q

what is the hardy-weinberg principle?

A

the original proportions of the genotypes in a population will remain constant from generation to generation as long as five assumptions are met

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8
Q

what are the five assumptions that must be met for hardy-weinberg?

A
  1. no mutation: DNA not changing
  2. no gene flow: no population mixing
  3. random mating
  4. large population size
  5. no natural selection
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9
Q

what must the frequencies of alleles always equal, whether the population is in HW equilbrium or not?

A

1, so homozygous dominant + heterozygous + homozygous recessive = 1

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10
Q

a population NOT in HW equilibrium indicates that one or more of the 5 evolutionary agents are operating in a population. list those 5 agents

A
  1. DNA mutation
  2. gene flow occurring
  3. mates chosen
  4. small population
  5. natural selection
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11
Q

what is the ultimate source for variation?

A

mutation

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12
Q

why isn’t mutation a strong evolutionary driver?

A

it happens too rarely

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13
Q

what is one of the most potent agents of change?

A

gene flow

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14
Q

does gene flow occur because of seasonal migration?

A

no because

  1. movement of the entire population
  2. not during a reproductive period
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15
Q

what is nonrandom mating?

A

mating with specific genotypes

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16
Q

what are the 2 types of nonrandom mating?

A
  1. assortative mating

2. disassortative mating

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17
Q

what is assortative mating?

A

between phenotypically similar individuals, increasing homozygotes

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18
Q

what are the 2 kinds of assortative mating?

A
  1. inbreeding

2. self-fertilization

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19
Q

what is dissasortative mating?

A

between phenotypically different individuals, produces excess of heterozygotes

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20
Q

what is the only evolutionary agent that produces adaptive evolutionary changes?

Study These Flashcards
A

natural selection!

21
Q

what is natural selection?

Study These Flashcards
A

environmental conditions determine which individuals in a population produce the most offspring

22
Q

what are the 3 conditions for natural selection to occur? (basically Darwin’s 3 postulates)

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A
  1. variation must exist among individuals
  2. variation must result in differential survival of offspring
  3. variation must be genetically inherited
23
Q

is natural selection evolution?

24
Q

how is natural selection not evolution?

Study These Flashcards
A

it is a process by which change (evolution) MAY occur over time but it does NOT always have an evolutionary result

25
what is artificial selection?
a breeder selects for desired characteristics
26
will the offspring between different dog breeds be considered hybrids? why or why not?
no, because all dog breeds are the same species, capable of producing viable offspring = NOT hybrids
27
what is the problem with small populations?
genetic drift
28
what is genetic drift?
when frequencies of particular alleles may change by chance alone, very random
29
what are the 2 kinds of genetic drift?
1. founder effect | 2. bottleneck effect
30
what is the founder effect?
when a small group is isolated or displaced from the original population, form a new population with a small allelic pool; like the Amish
31
what is the bottleneck effect?
a sudden, drastic reduction in population and gene pool size, like from a natural disaster, disease, or decreased prey
32
what is fitness?
a phenotype with greater fitness usually increases in frequency; most fit is given a value of 1
33
what 3 things is fitness of combination of?
1. survival: how long an organism lives 2. mating success: how often the organism mates 3. number of offspring per mating that survive
34
what are the 3 types of selection acting on traits affected by multiple genes?
1. directional 2. stabilizing 3. disruptive
35
what is disruptive (diversifying) selection?
acts to eliminate intermediate types, left with extremes= bimodal distribution
36
give an example of disruptive selection
predation and food pressures on body size; smaller means less food required and can hide larger can gather more food and get away from predators
37
what is directional selection?
acts to eliminate one extreme from an array of phenotypes
38
give an example of directional selection
Darwin's finches' beaks changing with climate
39
what is stabilizing selection?
acts to eliminate both extreme phenotypes; favors intermediates; distribution gets narrower
40
give an example of stabilizing selection
birthweight in humans
41
what is oscillating selection? give an example
one phenotype favored at a time, another phenotype favored at another; moth colors in the UK before, during, and after the industrial revolution
42
what is frequency dependent selection?
favors phenotypes that are either common (positive frequency dependent selection) or rare (negative frequency dependent selection)
43
does positive or negative FD selection increase or decrease variation?
look in book to answer
44
what is sexual dimorphism?
high degree of differences in outward appearance of females and males
45
why do females tend to have a greater investment in producing offspring?
they evaluate male secondary sexual characteristics to choose which potential mate has "better" genes
46
can more than one evolutionary agent be present in a population? if so, what are the results of such interactions?
yes, and it means evolution is not a guarantee; it takes a long time
47
does evolution have a purpose?
no, it is not changing a population into a preconceived ideal
48
what is the only evolutionary agent that is adaptive and results in a more fit population?
NATURAL SELECTION
49
what can gene flow and genetic drift actually do to a population's fitness?
may actually decrease it

Zoology (7 decks)

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