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Biology🧪🌱💦 > Lecture 19 > Flashcards

Lecture 19 Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

Does evolution occur in individuals or populations?

A

Evolution occurs in populations over successive generations, not within individual lifetimes (NOT individuals)

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2
Q

What are populations in the context of evolution?

A

Populations consist of all individuals of the same species living in a specific area at the same time, exhibiting variations in traits, some of which are inherited.

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3
Q

How does evolutionary change occur?

A

from one generation to the next, primarily through genetic variations

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4
Q

Why is genetics considered the basis of evolution?

A

Genetics determines how traits are passed from one generation to the next

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5
Q

What did Darwin not understand regarding the transmission of traits?

A

Darwin lacked an understanding of how traits were inherited from one generation to the next.

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6
Q

Between Darwin and Mendel, What did each talk about? (to explain evolution)

A

Darwin = NAtrual selection to explain evolution
Mendel = Principles of inheritance

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7
Q

What did both of these Theories come about?

A

Population Genetics

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8
Q

What is Population Genetics?

A

Science that studies the process of microevolution (Science that studies the process of microevolution)

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9
Q

What is Microevolution?

A

Is a change in the genetic makeup of a
population from generation to generation

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10
Q

Evolutionary change below what level?

A

below the species level

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11
Q

Can microevolution eventually lead to macroevolution?

A

YES

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12
Q

Why is this considered microevolution?

A

because although it doesn’t result in the formation of a new species, the genetic makeup of the population changes significantly

(no new species BUT genetics differ)

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13
Q

Describe the scenario of the abandoned mine.

A

The soil is rich in toxic heavy metals, allowing only grass seeds with alleles for heavy-metal tolerance to germinate, grow, and reproduce.

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14
Q

What happens to the offspring of plants with heavy-metal tolerance?

A

These plants tend to produce offspring with metal-tolerant traits.

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15
Q

What is the consequence of this selective pressure on the population? (over time)

A

the frequency of the allele for heavy-metal tolerance increases in the population

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16
Q

How has the genetic makeup of the population changed?

A

non-resistant alleles were dominant, but over time, heavy-metal-resistant alleles became dominant in that area.

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17
Q

What is Macroevolution? (in simple terms)

A

new species, new groups

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18
Q

What defines the gene pool of a population?

A

alleles for all the loci present in the population

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19
Q

How many alleles do diploid organisms typically have at each genetic locus?

A

two alleles at each genetic locus

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20
Q

Why do individuals within a population exhibit variations in traits?

A

due to genes coming in different allelic forms

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21
Q

How do individuals contribute to the gene pool of a population?

A

Each individual contributes only a small fraction of the alleles present in the population’s gene pool.

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22
Q

Provide an example of genetic variation in humans.

A

Humans exhibit genetic variation in traits such as hair color, eye color, etc., which result from different allelic forms of genes.

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23
Q
A
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24
Q

What is Genotype frequency?

A

The proportion of a particular genotype in the population

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25
Q

What is Allele frequency?

A

proportion of a specific allele in a population

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25
Q

What defines genetic equilibrium in a population? (when does it occur?)

A

occurs when the frequencies of alleles and genotypes do not change from one generation to the next.

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26
Q

How does the Hardy-Weinberg principle relate to genetic equilibrium?

A

The Hardy-Weinberg principle states that allele and genotype frequencies remain constant over generations in the absence of evolutionary influences, indicating genetic equilibrium.

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27
Q

What is the significance of genetic equilibrium?

A

population is not evolving for the gene locus being studied

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28
Q
A
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28
Q

Describe a population that is not at genetic equilibrium.

A

A population experiencing changes in allele frequencies over generations is not at genetic equilibrium and is undergoing evolution.

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29
Q

How does genetic equilibrium relate to the Hardy-Weinberg principle?

A

The Hardy-Weinberg principle serves as a mathematical model to determine whether a population is at genetic equilibrium or if evolution is occurring.

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30
Q

What conditions characterize a population in Hardy-Weinberg equilibrium?

A

all male-female matings occur randomly, leading to stable allele frequencies over generations.

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30
Q

How does the Hardy-Weinberg principle help understand population genetics?

A

The Hardy-Weinberg principle provides a BASELINE expectation for genotype and allele frequencies in a population that is not undergoing evolutionary changes, offering insight into population genetics.

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31
Q

Why do populations rarely stay in Hardy-Weinberg equilibrium in nature?

A

Due to various evolutionary pressures like natural selection, genetic drift, and gene flow, which alter allele frequencies.

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31
Q

What’s the significance of identifying populations in Hardy-Weinberg equilibrium?

A

It helps understand evolutionary processes and factors influencing genetic variation.

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32
Q

How can you calculate the value of one allele frequency if you know the other?
(what is the equation?)

A

p + q = 1

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33
Q

In this equation: p + q = 1
What is p and what is q?

A

p = one allele frequency
q = represents the other

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34
Q

If p equals 0.7, what is the value of q?

A

q = 0.3

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35
Q

Explain the significance of squaring both sides of the equation p + q = 1.

A

It helps describe the relationship between genotype frequencies, comparing the frequencies of homozygous dominant (p²), heterozygous (2pq), and homozygous recessive (q²) genotypes.

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35
Q

How is the equation p² + 2pq + q² = 1 used in population genetics?

A

It represents the distribution of genotype frequencies in a population, ensuring that the sum of all genotype frequencies equals 1.

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36
Q

What does each term in the equation
p² + 2pq + q² represent?

A

p² = the frequency of homozygous dominant genotypes (AA)
2pq = the frequency of heterozygous genotypes (Aa)
q² = the frequency of homozygous recessive genotypes (aa).

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37
Q

How can you simplify this answer?

A

p² = homozygous DOMINANT (AA)
2pq = heterozygous genotypes (Aa)
q² = homozygous RECESSIVE (aa).

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38
Q

Which equation is used fro genotype frquencies?

A

p² + 2pq + q² = 1

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39
Q

Which equation is used for allele frequencies?

A

p + q =1

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40
Q

What is the particularity about the allele frequencies?

A

For locus with only 2 ALLELES

41
Q

When is a population considered to be at genetic equilibrium?

A

when the distribution of alleles conforms to the equation p² + 2pq + q² = 1.

42
Q

What does the Hardy-Weinberg principle of genetic equilibrium tell us?

A

It predicts the expectations when a sexually reproducing population is not evolving.

43
Q

What are the conditions required for genetic equilibrium to occur? (5)

A

Random mating
No mutation
No natural selection
Extremely large population size
No migration (no gene flow)

44
Q

Do real populations often meet the conditions for genetic equilibrium?

A

NO

45
Q

What does the degree of departure between observed and expected allele frequencies by the Hardy-Weinberg principle indicate?

A

It indicates the amount of evolutionary change.

46
Q

Name 5 factors causing microevolution:

A
  • mutations
  • sexual recombination
  • natural selection
  • Genetic Drift
  • Gene flow
47
Q

What is evolution?

A

Changes in allele or genotype frequencies within a population over generations.

48
Q

What do we call a change in the nucleotide sequence of an organism’s DNA?

A

Mutation!

49
Q

How do new genes and alleles originate?

A

New genes and alleles originate only by mutation.

50
Q

Where do most mutations occur?

A

most in somatic cells (not gametes)

51
Q

Can mutations in somatic cells be passed on to offspring?

A

NO

52
Q

Which mutations can be passed on to offspring?

A

only mutations in GAMETES

53
Q

What is the typical mutation rate in animals and plants? (one in every ______ genes)

A

The mutation rate tends to be low in animals and plants, averaging about one in every 100,000 genes per generation.

54
Q

In which organisms are mutations more rapid?

A

in microorganisms

55
Q

Name an important microorganism

A

Bacteria

56
Q

What is sexual recombination?

A

process by which genetic material from two parents is combined to produce offspring

57
Q

With unique or identical combinations of alleles?

A

With UNIQUE combinations

58
Q

Sexual recombination contributes to WHAT?

A

genetic variation

59
Q

Is sexual recombination more important than mutation in producing genetic differences?

A

YES

60
Q

What is the significance of genetic variation in evolution?

A

the raw material for natural selection to act upon

61
Q

What does genetic variation lead to?

A

to adaptation and evolutionary change

62
Q

Does the presence of genetic variation guarantee evolution?

A

no, not necessarily

63
Q

Evolution also depends on what other factors? (3)

A

natural selection, genetic drift and gene flow

64
Q

What is differential success in reproduction?

A

the phenomenon where certain alleles are passed to the next generation in greater proportions due to the reproductive success of individuals carrying those alleles.

65
Q

How does differential success in reproduction affect allele frequencies?

A

Alleles linked to advantageous traits increase in frequency, while those tied to less favorable traits decrease.

66
Q

Can you give an example of natural selection?

A

Sure, like predators favoring prey with certain traits, causing those traits to become more common in the population over time.

67
Q

What are random evolutionary changes in a population?

A

They describe unpredictable fluctuations in allele frequencies from one generation to the next.

68
Q

How do random evolutionary changes affect genetic variation?

A

They can DECREASE genetic variation within a population
They can INCREASE genetic differences among different populations.

69
Q

What influences the likelihood of random evolutionary changes?

A

The size of the population sample, with smaller samples having a greater chance of deviation from predicted results.

70
Q

What are the two situations that may result in genetic drift in small population sizes?

A

a) Bottleneck effect
b) Founder effect

71
Q

What is the bottleneck effect?

A

Reduction in population size due to a disaster or other event.

72
Q

How does the bottleneck effect occur?

A

When a large population is drastically reduced, leading to random fluctuations in allele frequencies.

73
Q

What happens to alleles during the bottleneck effect? (3)

A

overrepresented, underrepresented or lost entirely.

74
Q

How does genetic drift continue to change the gene pool after a bottleneck event?

A

Genetic drift persists until the population size is large enough to counteract chance fluctuations.

75
Q

When does the bottleneck effect cease to influence the population’s genetic makeup?

A

When the population size becomes large enough to stabilize allele frequencies through genetic drift.

76
Q

What is the founder effect?

A

When a small group establishes a new population with limited genetic variation.

77
Q

How does the founder effect occur?

A

When a small number of individuals migrate or become isolated, establish a new colony.

78
Q

What happens to genetic variability during the founder effect?

A

The new population exhibits allele frequencies different from the original population due to the limited genetic diversity brought by the founding individuals.

79
Q

Can you provide an example of the founder effect?

A

The descent of 8000 individuals from only three couples of Old Order Amish, resulted in a high frequency of a rare recessive trait like dwarfism.

80
Q

What is gene flow?

A

The movement of fertile individuals between populations, results in the transfer of alleles.

81
Q

How does gene flow affect genetic variability?

A

It can lead to the loss of alleles in one population and the gain of alleles in another, thereby altering genetic variability.

82
Q

What is the impact of gene flow on population differences?

A

It tends to reduce differences b/w populations

83
Q

How does it reduce differences? (by what?)

A

by mixing individuals and their alleles

84
Q

What does gene flow counteract other evolutionary forces? (2)

A

It can counteract genetic drift and natural selection

85
Q

How does gene flow counteract other evolutionary forces?

A

by introducing new alleles and reducing genetic differentiation between populations.

86
Q

What is one outcome of gene flow? (+ due to what?)

A

The increased genetic variability within populations is due to the influx of new alleles.

87
Q

What is natural selection?

A

It’s the process where organisms with certain traits survive and reproduce better than others.

88
Q

How does natural selection lead to adaptation?

A

By favoring advantageous traits in a population over time.

89
Q

What are the factors causing microevolution? (5)

A

Mutations, sexual recombination, natural selection, genetic drift, and gene flow.

90
Q

How does natural selection differ from other mechanisms of evolution?

A

It’s non-random and adaptive, selecting traits beneficial for survival and reproduction.

91
Q

What is the ultimate outcome of natural selection?

A

GRADUAL adaptation of a population to its environment.

92
Q

Natural Selection can alter frequencies, what are the 3 different subcategories of Natural selection?

A
  • Directional selection
  • Disruptive selection
  • Stabilizing selection
93
Q

Which one Favors intermediate variants (acts against extreme phenotypes)

A
  • Stabilizing selection
94
Q

Which one favors individuals at one end of the
phenotypic range

A
  • Directional selection
95
Q

What is Disruptive selection then? (what does it favor?)

A

Favors individuals at BOTH extremes of the
phenotypic range

96
Q

How does sexual reproduction contribute to genetic variation?

A

unique combination of alleles inherited from two parents.

97
Q

What are the 3 mechanisms involved in generating genetic diversity through sexual reproduction?

A
  • crossing over
  • independent assortment
  • random fertilization
98
Q

Why does sexual reproduction typically result in fewer offspring compared to asexual reproduction?

A

B/c it requires the union of two gametes, which can limit the number of offspring produced.

99
Q

If sexual reproduction is a handicap, why has it persisted?

A

it produces genetic variation that may aid in
disease resistance

100
Q

Is this long or short-term?

A

SHORT-term

101
Q

What is sexual selection?

A

natural selection for mating success

102
Q

What can sexual selection result in?

A

sexual dimorphism

103
Q

What is sexual dimorphism?

A

marked differences between the sexes in secondary sexual characteristics

104
Q

What are the 2 types of sexual selection?

A
  • INTRAsexual selection
  • INTERsexual selection
105
Q

What is intrasexual selection?

A

Direct competition among individuals of one sex for mates of the opposite sex.

106
Q

Can you explain intersexual selection?

A

It occurs when individuals of one sex, often females, are selective in choosing their mates from individuals of the other sex.

Biology🧪🌱💦 (21 decks)

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