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BIOLOGY 108 TEST #4 > The Evolution of Populations > Flashcards

The Evolution of Populations Flashcards

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1
Q

Do individuals evolve?

A

NO, natural selection acts on individuals, however, populations are what evolve over time.

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2
Q

What is microevolution? What is the primary thing that contributes to microevolution?

A

A change in allele frequencies of a population over time.

Genetic variations in populations contribute to microevolution

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3
Q

What are the three main mechanisms that cause allelic frequencies to change? What is a fourth not so common cause? What must be present for the three main things to occur? How does natural selection differ from the other three?

A
  1. Natural selection
  2. Genetic Drift
  3. Gene flow

4th is mutation

Genetic variation must be present for the first 3.

  • natural selection is the only one that consistently improves the match between the organisms and their environment (adaptive evolution)
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4
Q

Does genetic variation occur in individuals in populations of all species?

A

YES

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5
Q

Are variations in phenotype always heritable? Example?

A

NO

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6
Q

What is the difference between discrete and quatitative characters? Examples?

A

Discrete - are either-or characteristics (purple or white flowers)

Quantitative - vary along a continuum within a population (skin color)

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7
Q

What are the two levels that geneticists measure genetic variationin a population?

A
  1. whole-gene level (gene variability)
  2. molecular level (nucleotide variability)
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8
Q

What is one way that gene variability is quantified? How do you calculate this?

A

Their average heterozygosity which is the average percent of loci that are heterozygous in a species.

take the number of heterzygotic genes and divide by total number of genes to get the percentage.

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9
Q

What must be present for selection to occur?

A

Multiple alleles for a given locus.

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10
Q

Can species exhibit geographical differences in variation between gene pools of separate populations or population subgroups?

What is an example of this geographic variation?

A

YES

there are several populations of mus musculus that have eveolved in isolation from one another on an island. They now have different karyotypes with different chromosomes fused together.

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11
Q

What is the example of geographic variation known as a cline?

A

This is a graded change in a trait along a geographic axis.

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12
Q

Did Darwin know about genes when he wrote his paper?

A

NO, but it set the stage for understanding the genetic differences upon which evolution is based

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13
Q

What are the two processes that produce variation in gene pool that contribute to differences among INDIVIDUALS?

A

mutation and sexual reproduction

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14
Q

What is a mutation?

A

Changes in nucleotide sequence of DNA that can cause new genes and alleles to arise.

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15
Q

What is a point mutation? Is this always harmful?

A

A change in one base in a gene.

These are usually only slightly harmful, but they can sometimes make the individual better suited for their environment, enhancing their reproductive success.

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16
Q

Are mutations that delete, disrupt, or rearrange loci typically more harmful than a simple point mutation? Are they ALWAYS harmful?

A

YES

They arent always harmful, some may even be beneficial.

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17
Q

Are mutation rates high in plants and animals? What is the mutation rate? Where are mutations found to be higher?

A

NO

1/100,000 genes per generation

Higher in microorganisms and viruses, especially RNA viruses.

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18
Q

What is moe important in producing genetic differences that make adaptation a possibility, mutation or sexual reproduction?

A

Sexual reproduction.

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19
Q

What are the 3 mechanisms of sexual reproduction that contribute to the shuffling of alleles?

A
  1. Crossing over
  2. Independent assortment
  3. Random fertilization
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20
Q

What is a population?

A

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

21
Q

What is a gene pool?

A

The total aggregate of genes in a population at any given time. Consists of all gene loci in all individuals.

22
Q

What must the sum of all allele frequencies for a loci in the population equal?

A

1

This holds true whether there are 2 or even more alleles

23
Q

What is the equation for ALLELE frequency?

A

p + q = 1

p = dominant allele

q = recessive allele

24
Q

What does the Hardy-Weinberg principle describe its population as?

A

as not evolving

Stating that the frequencies of alleles and genotypes in a populations gene pool remains constant from generation to generation.

25
Q

Why does mendelian segregation and recombination need to be present in harvey-weinberg equilibrium?

A

This ensures preservation in genetic variation of the population.

26
Q

Harvey Weinberg equilibrium?

A

Not evolving

Mendelian segregation and recombination of genes present.

27
Q

Do allele frequencies change in a population that is in HW equilibrium?

A

NO

28
Q

Understand p2 + 2pq + q2 = 1 in relation to this punnett square.

A

DO IT

See the allelic frequncy and how it relates to the homozygous and heterozygous outcomes and the math involved.

29
Q

How do you calculate the genotype frequencies of alleles of the same loci for a population?

A

p2 + 2pq + q2 = 1

p2 = homozygous dominant

pq = heterozygous (multiply by 2 becuase there are two ways a heterozygote occurs)

q2 = homozygous recessive

30
Q

Are real population in HW equilibrium?

A

NO, allele and genotype frequencies change over time.

HW is a hypothetical population

31
Q

What are the 5 conditions that must be met for the harvey weinberg theorem to be valid?

A
  1. population is large (decreases effect of chance changing allelic frequency)
  2. Matings are random (no preference for a particular phenotype)
  3. No net changes in gene pool due to mutation (mutation from A to a = mutations from a to A)
  4. No migration of individuals in and out of the population, NO GENE FLOW (trasfer of alleles between populations)
  5. No natural selection, all genotypes are equal in reproductive success.
32
Q

Can you use HW equation to estimate the percentage of human population carrying an allele for an inherited disease? Example?

A

YES

If 1/10,000 babies in US is born with PKU, which is a recessive disease, how many individuals in US are carriers of PKU?

  • This means the occurence is = q2 = 1/10,000 = 0.0001
  • SO find the square root of 0.0001 = 0.01
  • This means that p = 1 - q which = 1 - 0.01 = 0.99
  • A carrier is heterozygous, which is 2pq, so, p2 + 2pq + q2 = 1
  • 2(0.99 x 0.01) = 0.0198 OR about 2% are carriers.
33
Q

What are the three major factors that can alter allele frequencies and bring about evolutionary change?

A
  1. Natural selection - differential success results in certain alleles being passed on to next generation in greater proportions, ADAPTIVE EVOLUTION.
  2. Genetic drift - A chance event cause allele frequencies to fluctuate from one generation to another, generally reduces variation. through loss of alleles (bottleneck and founder effects).
  3. Gene flow - Genetic additions or subtractions from a population (immigration and emigration), can cause a population to gain or lose alleles.
34
Q

What is the form of genetic drift known as the bottleneck effect?

A

This is a sudden reduction in population size due to a change in the environment.

This may make the gene pool differ from the original populations gene pool.

35
Q

Look at this picture of the bottleneck effect in Illinois of the prairie chicken.

A

lkjg

36
Q

Understand this picture of genetic drift between multiple generations.

A

kiug

37
Q

Describe the form of genetic drift known as the founder effect.

A

This occurs when a few individuals become isolated from the larger population. The allele frequencies in the smaller founder population can differ from that of the larger population.

38
Q

What are the 4 major effects that genetic drift will have?

A
  1. Effect is more significant the smaller the population.
  2. Causes allele frequencies to change at random.
  3. Can lead to a loss of genetic variation within populations.
  4. Can cause harmful alleles to become fixed.
39
Q

What is the effect of gene flow?

A

Causes a population to gain or lose alleles, with a tendency to reduce differences between populations over time.

40
Q

What accumulates and maintains favorable genotypes in the population?

A

Natural selection

41
Q

IS natural selection based on survival of the fittest or struggle for survival? Or is it more subtle than this?

A

NO, it IS more subtle.

42
Q

What is relative fitness?

A

This is the contribution an individual makes to the gene pool of the next generation relative to the contribution of other individuals.

43
Q

Natural selection chooses genotypes based on the phenotypes they produce, what are the 3 modes of selection the natural selection has?

A
  1. Directional - favors individuals at one end of the phenotypic range
  2. Disruptive - favors individuals at both extremes of the phenotypic range
  3. Stabilizing - favors intermediate variants and acts against extreme phenotypes
44
Q

What is sexual selection? What can it result in? What are the two types of sexual selection
?

A
  • THis is the natural selection for mating success

This can result in sexual dimorphism which is a marked difference between the sexes in secondary sex characteristics.

  1. Intrasexual selection - competition among individuals of one sex for mates of the opposite sex.
  2. Intersexual selection - When individuals of one sex (females) are choosy in selecting their mates from individuals of the opposite sex. Usually depends on the showiness of the males appearance.
45
Q

How does diploidy help to preserve genetic variation?

A

Hidden recessive alleles are preserved.

46
Q

What is balancing fever? An example?

A

This is when natural selection maintains stable frequencuies of two or more phenotypic forms in a population.

For example the sickle-cell allele causes mutated hemoglobin but also given resistance to malaria, so if someone is a carrier (heterozygote) then they will have the advantage the allele offers without having the disease.

47
Q

What is frequency dependent selection? Example?

A

The fitness of the morph declines if it becomes more common in the population.

A morph that increases the blue jays ability to hunt a specific moth population becomes less effective as more and more get the morph and the population declines making the morph less fit.

48
Q

What is neutral variation? Example?

A

Genetic variation that has no apparent selective advantage

DNA base differences that occur in untranslated parts.

49
Q

What are 4 reasons that natural selection cant fashion the perfect organism?

A
  1. Selection can only edit existing variations.
  2. Evolution is limited by historical contraints.
  3. Adaptations are often compromises.
  4. Chance, natural selection, and the environment all interact.

Natural selection is all based on a better than basis, evidence for evolution is seen with the many imperfections of the organisms it produces.

BIOLOGY 108 TEST #4 (5 decks)

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