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Flashcards in Chapter 23 Deck (67):
1

What determines phenotypic differences?

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

2

Where do new genes come from?

Mutation; gene duplication; genetic variation from sexual reproduction

3

Is mutation always harmful?

Not always, but in the case of point mutation usually

4

Reproduce quickly and have very short generation times

Prokaryotes

5

What are 3 mechanisms that cause allele frequency change?

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

6

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

Genetic drift

7

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

Genetic flow

8

What are the 3 modes of selection?

1) directional
2) disruptive
3) stabilizing

9

Favors individuals at extremes of phenotypic range

Directional selection

10

Favors individuals at both extreme ends

Disruptive selection

11

Favors intermediate variants within the phenotypic range

Stabilizing selection

12

What is a common misconception about organisms and evolution?

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

13

What cause genetic variation among individuals?

Differences in genes or other DNA segments

14

How can sexual reproduction result in genetic variation?

By recombining existing alleles

15

Can all mutations be passed on to offspring?

No, only mutations in cells that produce gametes

16

Mutation rates are often lower in ___ and higher in ___

Prokaryotes; viruses

17

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

Population

18

What does a gene pool consist of?

All of the alleles for all loci in a population

19

What makes a locus fixed?

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

20

Consists of changes in allele frequency in a population over time

Microevolution

21

Refers to broad patterns of evolutionary change above the species level

Macroevolution

22

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

Species

23

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

Reproductive isolation

24

How do prezygotic barriers block fertilization from occurring?

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

25

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

Habitat isolation

26

What do postzygotic barriers prevent?

The hybrid zygote from developing into a viable, fertile adult

27

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

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

28

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

Sexual and asexual species

29

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

Phylogenetic species concept

30

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

Polyploidy

31

What is the cause of genetic variation among individuals?

Caused by differences in genes or other DNA segments

32

When does the founder effect occur?

When a few individuals become isolated from a larger population

33

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

Increases; less

34

Genetic drift tends to ___ genetic variation through ___ of alleles

Reduce; loss

35

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

Adaptive

36

When one base changes in a gene

Point mutation

37

Can mutations that cause change in protein production be harmful?

Yes

38

All the alleles for all loci in a certain population

Gene pool

39

What is the formula for Hardy-Weinberg equilibrium?

p2+2pq+q2=1

40

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

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

41

Drastic reduction in population size because of changes in the environment

Bottleneck effect

42

Movement of alleles in populations

Gene flow

43

An improvement in the match between organisms and their environment

Adaptive evolution

44

Marked differences between the sexes in secondary sexual characteristics

Sexual dimorphism

45

When does heterozygotes advantage occur?

When heterozygotes have a higher fitness than both homozygotes

46

A change in allele frequencies in a population over generations

Microevolution

47

What are some reasons natural selection cannot fashion perfect organisms?

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

48

What causes genetic variation?

Differences in genes or other DNA segments

49

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

Homozygous or heterozygous

50

Genetic drift is significant in ___ populations

Small

51

Gene flow can ___ the fitness of a population

Decrease

52

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

Sickle-cell disease and malaria

53

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

Intersexual selection

54

Favors intermediate variants and acts against extreme phenotypes

Stabilizing selection

55

Favors individuals at one extreme end of the phenotypic range

Directional selection

56

Favors individuals at both extremes of the phenotypic range

Disruptive selection

57

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

Relative fitness

58

What are two examples of genetic drift?

Bottleneck effect and the founder effect

59

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

Intrasexual selection

60

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

Intersexual selection

61

Name some effects of genetic drift

-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

The product of inherited genotype and environmental influences

Phenotype

63

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 ___

Hardy-Weinberg equilibrium

64

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

Sexual selection

65

Recombination from crossing over in meiosis is the source of ___

Genetic variation

66

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

Cline

67

All geographic variation results from ___

Clines