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Bio152 > Chapter 23 > Flashcards

Chapter 23 Flashcards

1
Q

What determines phenotypic differences?

A

Changes in a single gene or influences from multiple genes along a continuum

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2
Q

Where do new genes come from?

A

Mutation; gene duplication; genetic variation from sexual reproduction

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3
Q

Is mutation always harmful?

A

Not always, but in the case of point mutation usually

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4
Q

Reproduce quickly and have very short generation times

A

Prokaryotes

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5
Q

What are 3 mechanisms that cause allele frequency change?

A

1) natural selection
2) genetic drift
3) gene flow

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6
Q

How allele frequencies often fluctuate unpredictably from one generation to the next, especially in smaller samples. This reduces genetic variation

A

Genetic drift

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7
Q

Movement of alleles among populations through the movement of fertile individuals/gametes. Reduces genetic variation over time.

A

Genetic flow

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8
Q

What are the 3 modes of selection?

A

1) directional
2) disruptive
3) stabilizing

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9
Q

Favors individuals at extremes of phenotypic range

A

Directional selection

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10
Q

Favors individuals at both extreme ends

A

Disruptive selection

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11
Q

Favors intermediate variants within the phenotypic range

A

Stabilizing selection

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12
Q

What is a common misconception about organisms and evolution?

A

That organisms evolve during their lifetimes. Only populations evolve, and that takes time

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13
Q

What cause genetic variation among individuals?

A

Differences in genes or other DNA segments

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14
Q

How can sexual reproduction result in genetic variation?

A

By recombining existing alleles

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15
Q

Can all mutations be passed on to offspring?

A

No, only mutations in cells that produce gametes

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16
Q

Mutation rates are often lower in ___ and higher in ___

A

Prokaryotes; viruses

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17
Q

A localized group of individuals capable of interbreeding and producing fertile offspring

A

Population

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18
Q

What does a gene pool consist of?

A

All of the alleles for all loci in a population

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19
Q

What makes a locus fixed?

A

If all individuals in a population are homozygous for the same allele

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20
Q

Consists of changes in allele frequency in a population over time

A

Microevolution

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21
Q

Refers to broad patterns of evolutionary change above the species level

A

Macroevolution

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22
Q

A group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring

A

Species

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23
Q

The existence of biological factors (barriers) that impede two species from producing viable, fertile offspring

A

Reproductive isolation

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24
Q

How do prezygotic barriers block fertilization from occurring?

A

1) impeding different species from attempting to mate
2) preventing successful completion of mating
3) hindering fertilization if mating is successful

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25
Q

When two species encounter each other rarely, or not at all, because they occupy different habitats, even though not isolated by physical barriers

A

Habitat isolation

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26
Q

What do postzygotic barriers prevent?

A

The hybrid zygote from developing into a viable, fertile adult

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27
Q

Give an example of how gene flow can occur between distinct species

A

The mating of a polar bear and a grizzly bear to make a grolar bear

28
Q

What types of species does the morphological species concept apply to?

A

Sexual and asexual species

29
Q

Defines a species as the smallest group of individuals on a phylogenetic tree

A

Phylogenetic species concept

30
Q

The presence of extra sets of chromosomes due to accidents during cell division

A

Polyploidy

31
Q

What is the cause of genetic variation among individuals?

A

Caused by differences in genes or other DNA segments

32
Q

When does the founder effect occur?

A

When a few individuals become isolated from a larger population

33
Q

Duplication of small pieces of DNA ___ genome size and is ___ harmful.

A

Increases; less

34
Q

Genetic drift tends to ___ genetic variation through ___ of alleles

A

Reduce; loss

35
Q

Natural selection can cause ___ evolution, an improvement in the match between organisms and their environment

A

Adaptive

36
Q

When one base changes in a gene

A

Point mutation

37
Q

Can mutations that cause change in protein production be harmful?

A

Yes

38
Q

All the alleles for all loci in a certain population

A

Gene pool

39
Q

What is the formula for Hardy-Weinberg equilibrium?

A

p2+2pq+q2=1

40
Q

What are the 5 conditions for non-evolving populations? (Conditions for Hardy-Weinberg equilibrium)

A

1) no mutations
2) random mating
3) no natural selection
4) very large population
5) no gene flow

41
Q

Drastic reduction in population size because of changes in the environment

A

Bottleneck effect

42
Q

Movement of alleles in populations

A

Gene flow

43
Q

An improvement in the match between organisms and their environment

A

Adaptive evolution

44
Q

Marked differences between the sexes in secondary sexual characteristics

A

Sexual dimorphism

45
Q

When does heterozygotes advantage occur?

A

When heterozygotes have a higher fitness than both homozygotes

46
Q

A change in allele frequencies in a population over generations

A

Microevolution

47
Q

What are some reasons natural selection cannot fashion perfect organisms?

A
  • can only work on existing variations
  • evolution is limited by historical constraints
  • adaptations are often compromises
  • chance, natural selection, and environment interact
48
Q

What causes genetic variation?

A

Differences in genes or other DNA segments

49
Q

If there are 2 or more alleles for a locus, diploid individuals can be what?

A

Homozygous or heterozygous

50
Q

Genetic drift is significant in ___ populations

A

Small

51
Q

Gene flow can ___ the fitness of a population

A

Decrease

52
Q

What can be caused by a mutation in the hemoglobin protein?

A

Sickle-cell disease and malaria

53
Q

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

A

Intersexual selection

54
Q

Favors intermediate variants and acts against extreme phenotypes

A

Stabilizing selection

55
Q

Favors individuals at one extreme end of the phenotypic range

A

Directional selection

56
Q

Favors individuals at both extremes of the phenotypic range

A

Disruptive selection

57
Q

Contribution an individual makes to the gene pool of the next generation, relative to the contributions of other individuals

A

Relative fitness

58
Q

What are two examples of genetic drift?

A

Bottleneck effect and the founder effect

59
Q

Organisms of one sex directly compete for mates of the opposite sex

A

Intrasexual selection

60
Q

Organisms of one sex are choosy in their selection of the opposite sex

A

Intersexual selection

61
Q

Name some effects of genetic drift

A
  • occurs in small populations
  • causes allele frequencies to change at random
  • loss of genetic variation in a population
  • causes harmful alleles to be fixed
62
Q

The product of inherited genotype and environmental influences

A

Phenotype

63
Q

In a population where gametes contribute to the next generation randomly and Mendelian inheritance occurs, allele and genotype frequencies remain constant from generation to generation. Such a population is in ___

A

Hardy-Weinberg equilibrium

64
Q

Natural selection for mating success. Can result in sexual dimorphism, marked differences between the sexes in secondary sexual characteristics

A

Sexual selection

65
Q

Recombination from crossing over in meiosis is the source of ___

A

Genetic variation

66
Q

A trend toward the decrease in size of plants on slopes of a mountain as altitude increases is an example of ___

A

Cline

67
Q

All geographic variation results from ___

A

Clines

Bio152 (12 decks)

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