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Biology 221 > Chapter 23 > Flashcards

Chapter 23 Flashcards

The Evolution of Populations

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1
Q

What is microevolution?

A

A change in allele frequencies in a population over generations.

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2
Q

What are the 5 main mechanisms which cause allele frequency change?

A
  1. Mutations
  2. Genetic Drift
  3. Natural Selection
  4. Gene Flow
  5. Sexual Selection
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3
Q

What is a mutation?

A

A random change in the nucleotide sequence of DNA. only mutations in gametes can be passed on.

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4
Q

What is Genetic Drift?

A

Chance events that alter allele frequency.

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5
Q

What is Gene Flow?

A

The transfer of alleles between populations.

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6
Q

What is Natural Selection?

A

Adaption of organisms to best suit their enviornment.

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7
Q

What is Sexual Selection?

A

Natural selection chosen by traits desirable from the other sex leading to reproduction.

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8
Q

What is an example of a Mutation?

A

When on base pair is swapped causing genetic code telling ribosome to detach even though the whole nucleotide sequence is not read yet.

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9
Q

What is an example of Genetic Drift?

A

If there are mostly white rabbits where it snows a lot and just a few brown rabbits, there could be a lot less snow if non that year so the white rabbits no longer suit the environment. This means the frequency of brown rabbits would rise significantly and the white rabbits population would plummet.

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10
Q

What is an example of Gene Flow?

A

Polar bears migrate from ice cave where they to the forest where brown bears live and they interbreed.

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11
Q

What is an example of Natural Selection?

A

Same bird species adapting to environment across the different islands and continents.

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12
Q

What is an example of Sexual Selection?

A

Peacock tails that are really bright on males is more attractive to the females making the bright male tales more frequent throughout peacock population.

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13
Q

What is neutral variation in Mutations?

A

No positive or negative change made.

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14
Q

Explain “It is the population, not the individual that evolves.”

A

It takes many individuals with genetic differences mating and reproducing for a species to evolve, not just one individual or organism can evolve a species.

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15
Q

Why are the majority of point mutations harmless?

A

If only one base in a nucleotide sequence is changes it can be harmless because those nucleotide sequences can be read the same genetically because of how redundant genetic code is. It can also be in a noncoding section of the sequence, if it doesn’t code it can’t hurt the organism.

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16
Q

What are the 3 types of point mutations?

A
  1. Silent Mutations
  2. Missense Mutations
  3. Nonsense Mutations
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17
Q

What is a Nonsense Mutation?

A

When the nucleotide is prematurely prevented from being read because a stop codon has happened due to the mutation.

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18
Q

What is a Missense Mutation?

A

A mutation that leads to an amino acid being read or switched to another amino acid.

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19
Q

What is a Silent Mutation?

A

When the change in a gene doesn’t affect the corresponding amino acid.

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20
Q

What is the significance of Transposons in the generation of genetic variability?

A

If the genetic mutation in the transposons isn’t harmful then it’ll be passed on, doubling inherited genes.

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21
Q

How does sexual recombination generate gene variability?

A

Crossing Over, Random Fertilization, and Independent Assortment all contribute to genetic variability.

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22
Q

What is a population?

A

All members of a species in an area.

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23
Q

What is a species?

A

A group of organisms that can reproduce with one another in nature and produce fertile offspring for more than one generation.

24
Q

What is a gene pool?

A

All the genes in a population.

25
Q

What are the 5 conditions that must be met for a population to remain in Hardy-Weinberg equilibrium for a particular gene.

A
  1. No Mutations.
  2. Large Populations.
  3. No Gene Flow.
  4. Random mating.
  5. No Natural Selection.
26
Q

What does “Only natural selection leads to the adaptation of organisms to their environment.” mean?

A

A single organism simply cannot evolve by their self. Natural selection is partly random and partially not, so no individual can really control their role, much less evolve by themself.

27
Q

What is the role of role of population size in genetic drifts?

A

Genetic Drift is when a large change in population triggers reduced genetic variation. When there are less organisms to choose from the gene pool can change drastically very suddenly. In larger population losing 30 animals of a specific genotype wouldn’t be a big deal, but in smaller populations it would entirely change gene pool and genetic diversity.

28
Q

What is the bottleneck effect?

A

When a sudden reduction of population size occurs, due to environmental factors. Gene pool is affected.

29
Q

What is the founder effect?

A

The founder effect is when a few individuals of a large population become isolated. Due to this isolation the allele frequency is different from the rest of the large population.

30
Q

What is an example of the founder effect?

A

The Marine Iguana of the Galapagos Islands looks to have diverged from Mainland Iguanas. The marine Iguanas dive down for the algae and have adapted physically to better fit their environment.

31
Q

What is an example of the bottleneck effect?

A

When hunted animals go extinct or close to it and the smaller pool has less diversity and the gene pool becomes almost randomized.

32
Q

What is the difference between the bottleneck effect and the founder effect?

A

The bottleneck is when the population size gets reduced to such a point that the genotype pool is drastically changed. The founder is when smaller isolated animals start a new population, that gene pool and even their genetics are vastly different than that initial population that these new animals branched off from.

33
Q

How can gene flow work to reduce genetic differences between adjacent populations?

A

Gene flow reduces genetic diversity in between adjacent species because the more movement of genes between separate population (breeding), the more similar those populations become over time.

34
Q

What is relative fitness?

A

The contribution a single organism makes to the gene pool in terms of the next generations genes relative to the other organisms in the same generation.

35
Q

What is directional selection?

A

When natural selection favors individuals with one extreme phenotypic trait. Shifting the population towards that desired phenotypic trait.

36
Q

What is an example of directional selection?

A

If there is a change in environment from mild to cold temperatures, and there is a specific individual with a thicker fur, over time that one desired trait would multiply until it becomes a common allele.

37
Q

What is disruptive selection?

A

Is when the individuals on both ends of the extreme phenotype are more suited to the environment. The medium portion in the gene pool becomes smaller.

38
Q

What is an example of disruptive selection?

A

If there is a mice population that live amongst rocks, the spotted or splotchy mice don’t survive well, leading to the solid colored light and dark mice percentages rising.

39
Q

What is stabilizing selection?

A

Stabilizing selection is when the individuals at the extreme ends of the spectrum are wiped out or unsuitable for the environment.

40
Q

What is an example of stabilizing selection?

A

An example would be babies, if the baby is either to big or too small, mortality rates rise, leading to the gene pool mostly being a more average weight.

41
Q

What is intersexual selection?

A

Often called “mate choice” (usually female) when the individual of one sex chooses their mate.

42
Q

What is intrasexual selection?

A

Direct competition between individuals, usually males, to win the other sex.

43
Q

What is the difference between intrasexual and intersexual selection?

A

Intra is the competition between the mates, and Inter is when one individual picks their mate.

44
Q

What is sexual dimorphism?

A

Sexual dimorphism is when their are physical traits that are different depending on sex of the individual.

45
Q

What is an example of sexual dimorphism?

A

Male peacocks have very bold and bright feather to attract females, the women have duller feathers for discretion while nesting.

46
Q

How does female preferences for showy male traits may benefit the female?

A

They are attracted to that mate, and they can have more extravagant offspring.

47
Q

What is the cost of being a showy male?

A

Males that are showy have lower chances of survival due to factors like competition, and metabolic cost.

48
Q

What is the Heterozygote advantage?

A

That natural selection favors the heterozygote allele (Rr). Can occur from stabilizing or directional selection.

49
Q

What is the Frequency dependent selection?

A

When the more “fit” phenotype becomes too common, it declines due to natural selection.

50
Q

What is the genotype of sickle cell disease?

A
51
Q

What is the phenotype of sickle cell?

A
52
Q

What are the 4 main reasons that natural selection can not produce perfect organisms?

A
  1. Selection can only act on existing variations.
  2. Evolution is limited historically.
  3. Adaptations are often compromises.
  4. Chance, natural selection, and the enviorment interact.
53
Q

What are the main 3 events of Meiosis?

A
  1. Independent Assortment
  2. Crossing Over
  3. Random Fertilization
54
Q

What does natural selection act on?

A

Natural selection acts on individuals, but only populations can evolve.

55
Q

What is the good gene hypothesis?

A

The good gene hypothesis is that if a trait is related to quality of health, that that trait will become more frequent with each generation.

Biology 221 (10 decks)

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