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23 Flashcards

1
Q

microevolution

A

a change in allele frequencies in a population over generations

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2
Q

macroevolution

A

results in the formation of new species or large groups of living things

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3
Q

genotype

A

genetic makeup of any organism

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4
Q

phenotype

A

observable traits that an organism has (including physical characteristics and behavior)

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5
Q

genes come in varying forms called _____

A

alleles

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6
Q

the basis of evolution is ____

A

a change in the frequency of alleles in

a population

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7
Q

natural selection

A

The effects of the mutations on the survival and reproduction of organisms

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8
Q

population

A

a localized group of interbreeding individuals

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9
Q

gene pool

A

collection of alleles in the population

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10
Q

allele frequency

A

how common is that allele in the population

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11
Q

what are the conditions for the Hardy Weinberg equation?

A
  1. No mutations
  2. Random mating
  3. No Natural Selection
  4. Very large population size
  5. No gene flow
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12
Q

Mechanisms that cause evolution are

A
  1. mutation
  2. genetic drift
  3. gene flow
  4. natural selection
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13
Q

mutation

A

modifies allele frequencies by continually introducing new alleles. The alleles may be beneficial or detrimental or have no effects on fitness

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14
Q

genetic drift

A

causes allele frequencies to change randomly. In some cases, drift can cause alleles that decrease fitness to increase in frequency

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15
Q

gene flow

A

occurs when individuals leave one population, join another, and breed. Arriving individuals introduce new alleles and departing individuals remove alleles; resulting in change in allele frequencies

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16
Q

natural selection

A

increases the frequency of certain alleles—the ones that contribute to success in survival and reproduction

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17
Q

Genetic drift can have large effects on small populations through two common scenarios which are

A

– Founder effects

– Population bottlenecks

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18
Q

founder effect

A

a change in allele frequencies that occurs when a new population is established (i.e. a subpopulation migrates)

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19
Q

bottleneck effect

A

a sudden reduction in the number of alleles present in a population. By chance alone, certain alleles may be overrepresented among survivors, while others are underrepresented or absent.

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20
Q

genetic drift can

A
  1. …is significant in small populations
  2. …can cause allele frequencies to “drift”
    randomly
  3. …can lead to a loss of genetic variation within populations
  4. …can lead to the fixation of deleterious alleles
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21
Q

Gene flow can _____ the fitness of a population

A

increase

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22
Q

types of natural selection

A

directional, disruptive, stabilizing

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23
Q

directional

A

average phenotype of the population is changed in one direction. (favors one extreme)

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24
Q

disruptive

A

eliminates phenotypes near the average value. (favors extremes)

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25
Q

stabilizing

A

selection reduces both extremes in a population, so that there is no change in the average value of a trait over time and genetic variation is reduced. (favors average)

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26
Q

sexual selection

A

is a form of natural selection that can affect the frequency of alleles in a gene pool.
– It occurs when differences in reproductive success arise because of differential success in mating.

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27
Q

sexual dimorphism

A

a difference in secondary sexual characteristics between males and females

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28
Q

intrasexual selection

A

is direct competition among individuals of one sex (often males) for mates of the opposite sex

29
Q

Intersexual selection

A

often called mate choice, occurs when individuals of one sex (usually females) are choosy in selecting their mates
• Showiness of male appearance can increase a male’s chances of attracting a female while decreasing his chances of survival

30
Q

neutral variation

A

is genetic variation that does not confer a selective advantage or disadvantage

31
Q

preservation of genetic variation comes from

A

neutral variation, diploidy, balancing selection

32
Q

diploidy

A

in diploid eukaryotes,a considerable amount of genetic variation is
hidden from selection in the form of recessive alleles

33
Q

What is the smallest unit that can evolve?

A

populations

34
Q

natural selection acts on ____

A

individuals (inheritable traits)

35
Q

Describe the role of mutation in evolution.

A

New alleles can arise by mutation: a change in the nucleotide sequence of an organisms DNA

Some mutations can be harmful, others are not. Neutral variation- differences in DNA sequences that do not confer a selective advantage or disadvantage

36
Q

List 5 agents of change that can bring about evolution. What is it about natural selection that is unique compared to the other agents of change?

A
  1. Mutation
  2. gene flow
  3. nonrandom mating
  4. genetic drift
  5. natural selection

Natural Selection is the only mechanism acting alone can result in ADAPTATION.

37
Q

Most of the mechanisms lead to ____ of genetic diversity except for mutation

A

LOSS

38
Q

natural selection

identify whether they increase, decrease or have no effect on average fitness and genetic variation.

A

Natural selection: It favors certain beneficial alleles.
It can lead to maintenance, increase, or reduction of genetic variation.
Its effect on average fitness is that it can produce adaptation

39
Q

genetic drift

identify whether they increase, decrease or have no effect on average fitness and genetic variation.

A

It tends to reduce genetic variation, via loss or fixation of alleles.
Its effects on average fitness is that it reduces average fitness by the fixation of alleles or loss of alleles

40
Q

mutation

identify whether they increase, decrease or have no effect on average fitness and genetic variation.

A

It produces new alleles.
It increases genetic variation by introducing new alleles
It is random with respect to fitness. Mutations may be beneficial, detrimental, or may have no effect on fitness

41
Q

Gene flow

identify whether they increase, decrease or have no effect on average fitness and genetic variation.

A

Gene Flow may increase genetic variation by introducing new alleles or it may decrease variation by removing alleles.
Gene Flow may increase average fitness by introducing high-fitness alleles or decrease it by introducing low-fitness alleles

42
Q

biological fitness

A

the ability to survive to reproductive age, find a mate, and produce offspring.

43
Q

True or False—“Survival of the Fittest” is an accurate description of evolution by natural selection. Why or why not?

A

False.
Natural selection is not so much about which traits are beneficial and which traits are not as useful for a specific species. Rather, natural selection is much more about the number of offspring an organism leaves behind that reach a reproductive age or fitness. Natural selection is more about reproductive success than ruling out certain traits of certain species.

44
Q

Describe the general model for the evolution of resistance (among bacteria, or insects, or fungi etc)

A

Once the antibiotic is introduced before selection, all non-resistant organisms die off, than after selection the population consists of organisms that are able to resist the antibiotic, therefore the final population will consist of all resistant organisms

45
Q

Define gene flow, give an example.

A

the transfer of alleles into or out of a population due to movement of fertile individuals or their gametes

Human migration is transferring alleles between populations that were once isolated

46
Q

Is genetic drift more likely to happen in small or large populations?

A

Small populations

Since the population is small it has a more of possibility of losing alleles entirely. When this happens, the remaining alleles eventually become fixed.

47
Q

“The common phenotype is not necessarily the most adaptive”. Explain this statement.

A

Whether or not a trait is common has to do with how many copies of that gene version (or allele) are in the population. It has little or nothing to do with whether the trait is dominant or recessive

48
Q

what mechanism preserve genetic variation?

A
  1. Diploidy
  2. Heterozygote advantage
  3. Frequency-dependent selection
49
Q

diploidy

A

in diploid eukaryotes, a considerable amount of genetic variation is hidden from selection in the form of recessive alleles; heterozygotes can carry recessive alleles that are hidden from the effects of selection

50
Q

Heterozygote advantage

A

natural selection tends to maintain two or more alleles at that locus

51
Q

Frequency-dependent selection

A

fitness of a phenotype depends on how common it is in the population

52
Q

Natural selection changes allele frequencies because some _______ survive and reproduce more successfully than others.

A

individuals

53
Q

No two people are genetically identical, except for identical twins. The main source of genetic variation among human individuals is

A

the reshuffling of alleles in sexual reproduction.

54
Q

If the nucleotide variability of a locus equals 0%, what is the gene variability and number of alleles at that locus?

A

gene variability = 0%; number of alleles = 1

55
Q

There are 25 individuals in population 1, all with genotype AA, and there are 40 individuals in population 2, all with genotype aa. Assume that these populations are located far from each other and that their environmental conditions are very similar. Based on the information given here, the observed genetic variation is most likely an example of

A

genetic drift

56
Q

A fruit fly population has a gene with two alleles, A1 and A2. Tests show that 70% of the gametes produced in the population contain the A1 allele. If the population is in Hardy-Weinberg equilibrium, what proportion of the flies carry both A1 and A2?

A

0.42

p = 0.7
q = 0.3

2 (0.7 x 0.3) = 0.42

57
Q

Hardy Weinberg describes the gene pool of a population that is _____

A

NOT evolving

58
Q

Is the soapberry bug/golden rain tree example an illustration of microevolution or macroevolution?

A

Microevolution – population

59
Q

allele

A

Genes come in varying forms which are called alleles

60
Q

genetic variation

A

phenotypic variations are differences among individuals in the composition of their genes

61
Q

what are sources of genetic variation?

A
  1. mutation - formation of new alleles
  2. sexual reproduction
  3. altering gene number or position
62
Q

genetic variants can be produced rapidly in organisms with a _____

A

short generation time

63
Q

natural selection is the only mechanism that causes ____

A

adaptive evolution

64
Q

what are effects of genetic drift?

A
  1. significant in small populations
  2. causes allele frequencies to change randomly
  3. can lead to a loss of genetic variations
  4. can cause harmful alleles to become fixed
65
Q

what is biological fitness and how is it measured?

A

Ability of an individual to produce surviving, fertile offspring relative to that ability in other individuals in the population, measurable quantity

Count the number of healthy fertile offspring produced by different individuals in a population

Measures the reproductive success of an organism relative to others in a population

66
Q

relative fitness

A

the contribution an individual makes on the gene pool of the next generation relative to the contributions of other individuals.

selection acts more directly on the phenotype, than the genotype

67
Q

Most reproductive output =

A

highest fitness

68
Q

sexual selection

A

a process in which individuals with certain inherited characteristics are more likely than other individuals of the same sex to obtain mates

69
Q

reasons why natural selection can’t fashion perfect organism

A
  1. selection can act only on existing variations
  2. evolution is limited by historical constraints
  3. adaptations are often compromises

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