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Biology > Chapter 23 Microevolution > Flashcards

Chapter 23 Microevolution Flashcards

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1
Q

What is microevolution?

A

Change of life in allele frequencies in a population over generations

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2
Q

What are the 3 mechanical causes of allele frequency change?

A
  • natural selection
  • genetic drift
  • gene flow
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3
Q

What can only cause adaptive evolution?

A

Natural selection

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4
Q

What is a prerequisite for evolution?

A

Genetic variation in heritable traits

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5
Q

What is genetic variation?

A

Among individuals it’s caused by differences in genes or other DNA segments

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6
Q

What is a phenotype?

A

Physical appearance of genes

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7
Q

What is a genotype?

A

Genetic makeup code

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8
Q

What are some phenotypic differences determined by?

A

Determined by a single gene

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9
Q

What are other phenotypic differences determined by?

A

The influence of two or more genes, and varies along a continuum within a population

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10
Q

What is measured as gene variability or nucleotide variability?

A

Genetic variation

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11
Q

What also can cause a change in phenotypic variation?

A

Environmental influences

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12
Q

What kind of variation can only have evolutionary consequences?

A

Only genetically determined variation

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13
Q

When does the recombination of existing alleles happen?

A

Happens during the process of meiosis

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14
Q

What is a mutation?

A

Random change in nucleotide sequence of DNA

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15
Q

What is a point mutation?

A

Change in one base in a gene

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16
Q

What are the effects of a point mutation?

A
  • Varies in mutation can be harmful, beneficial, or neutral
  • Usually are hidden in recessive alleles
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17
Q

What is neutral variation?

A

Conferring no selective advantage or disadvantage in mutation

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17
Q
A
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18
Q

Where can neutral variation happen?

A

It can happen in point mutations in the noncoding region

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19
Q

Chromosomal Mutation

A

Mutations that delete, disrupt, or rearrange many loci that are typically harmful

20
Q

Duplication Mutation

A

Increases genome size and is usually less harmful
- can take on new function by further mutation

21
Q

Why are mutations rates higher in viruses compared to prokaryotes?

A

Due to rapid reproduction

22
Q

What is a population?

A

Localized group of individuals that’s capable of interbreeding and producing fertile offspring

23
Q

What is a gene pool?

A

Consists of all the alleles for all loci in a population

24
Q

What is a diploid organism?

A

The total number of alleles at locus is the total number of individuals times 2

25
Q

What is the Hardy-Weinberg formula?

A
  • p + q = 1
  • p^2 + 2pq + q^2 = 1
26
Q

What does the Hardy-Weinberg equation describe?

A

Describes the genetic makeup we expect for a population that’s not evolving at a particular locus.

27
Q

How do we know if a population may be evolving?

A

If the observed genotype of population differs from expectations under Hardy-Weinberg

28
Q

What is the Hardy-Weinberg Equilibrium?

A

Alleles and genotype frequencies remain constant from generation to generation

29
Q

What are the 5 conditions for a nonevolving population that are rarely met?

A
  1. no mutations
  2. random mating
  3. no natural selection
  4. extremely large population size
  5. no gene flow
30
Q

What is genetic drift?

A

Describes how allele frequencies fluctuate unpredictably from one generation to the next

  • tends to reduce genetic variation thru loss of alleles
31
Q

What is the founder effect?

A

Occurs when a few individuals become isolated from a larger population

32
Q

What is the bottleneck effect?

A

Sudden reduction in population size due to change in the environment

(such as changes due to natural disasters)

33
Q

What is relative fitness?

A

Contribution of an individual makes to the gene pool of the next generation

  • relative to the contributions of other individuals
34
Q

What is gene flow?

A

Consists of the movement of alleles among populations

35
Q

What are some effects of genetic drift?

A
  • significant in small populations
  • can cause allele frequencies to change at random
  • can lead to a loss of genetic variation within populations
  • can cause harmful alleles to become fixed
36
Q

What are some effects of gene flow?

A
  • can increase or decrease the relative fitness of a population
  • reduces genetic variation over time
37
Q

What are the 3 modes of selection?

A
  • directional selection
  • disruptive selection
  • stabilizing selection
38
Q

Directonal Selection

A

favors individuals at one extreme end of the phenotypic range

39
Q

Disruptive Selection

A

Favors individuals at both extreme ends of the phenotypic range

40
Q

Stabilizing Selection

A

Favors immediate variants and acts against extreme phenotypes

41
Q

Sexual selection?

A

natural selection for mating success that results in sexual dimorphism

42
Q

sexual dimorphism

A

Marked differences b/w the sexes in secondary sexual characteristics

43
Q

intrasexual selection

A

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

44
Q

intersexual selection

A

often called mate choice, occurs when individuals of one sex (usually females) are choosy in selecting their mates

45
Q

Balancing Selection

A

Occurs when natural selection maintains stable frequencies of two or more phenotypic forms in a population

  • includes: heterozygous advantage and frequency dependent selection
46
Q

Heterozygote Advantage

A

Occurs when heterozygotes have a higher fitness than do both homozygotes

  • results from stabilizing or directional selection
47
Q

Frequency-Dependent Selection

A

Fitness of a phenotype declines if it becomes too common in the population

48
Q

Why natural selection cannot fashion perfect organisms? (4 things)

A
  1. selection can act only on existing variations
  2. evolution is limited by historical constraints
  3. Adaptations are often compromises
  4. Chance, natural selection, and the environment interact

Biology (34 decks)

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