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Biology > 10.3 > Flashcards

10.3 Flashcards

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1
Q

What is a gene pool

A

consists of all the genes and they different alleles present in an interbreeding population

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2
Q

What is the allele frequency

A

measures how common an allele is in a population

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3
Q

How is the depth or richness of the gene pool measured

A

by the number of alleles and their relative frequencies

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4
Q

What is a species

A

a group of organisms that are genetically similar and can interbreed with one another and produce fertile offspring

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5
Q

What is a population

A

the individuals of the same species that livie in the same place at the same time

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6
Q

What does evolution require

A

the allele frequency to change with time in populations

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7
Q

What leads to evolution of a population

A

selective pressures

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8
Q

What happens when populations are isolated form one another

A

genetic drift and different selective pressures can cause the populations to evolve differently. Over time, when enough differences cumulate, the populations may speciate

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9
Q

What are selective pressures

A

environmental factors that can affect the rate of survival and reproduction of certain phenotypes

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10
Q

What are selective pressures caused by

A

both biotic and abiotic factors that change the rate of survival and reproduction of a segment of a population

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11
Q

What are three types of effects cause by selective pressures

A

Stabilising selection

Directional selection

Disruptive selection

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12
Q

What is stabilizing selection

A

ti is widespread and occurs when the existing variations that are beneficial are already common. Stabilizing selection acts against extremes of a trait, for example, the color of a sand crab. Seagulls prey on the crabs, and the more they deviate from the background color, the less likely it is to survive. New course may be reintroduced due to mutations but stabilizing selection exerted by seagulls will maintain the match between the color of crabs and the sand.

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13
Q

What is directional selection

A

occurs when one extreme of a trait offers a survival or reproductive advantage. The sand crabs living on the beach would experience directional selection if the background sand color changes, for example, if flooding covered the beach with darker colored silt, then darker colored cabs would have an advantage in avoiding predators and would survive longer and have more successful offspring. Dark color alleles would then become more common and light color alleles less common. Directional selection increases allele frequency’s at one phenotypic extreme and reduced them at the other

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14
Q

What is disruptive selection

A

the most frequent phenotype becomes a disadvantage and individuals at both extremes have bette rates of sruvvasl and reproduction. In the sand crab example., perhaps the female crabs inherit a genetic preference for males that stand out agains the sandy back-up. This type of preference is fairly common.

Choosing a mate that can survive even when it stands out suggest a very strong assortment of the alleles. In this case, crabs lighter and darker than the background would have the most success in passing their alleles to the next generation.

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15
Q

What selective pressures allow the population to remain in a single group

A

stabilising and directional

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16
Q

What is a genotype frequency

A

the number of individuals with a given genotype as proportion of the entire population

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17
Q

How to calculate allele frequency

A

P + q = 1

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18
Q

how to calculate genotype frequency

A

p^2 + 2pq + q^2 = 1

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19
Q

What is evolution

A

a cumulative change in heritable genetics chacrateristsics of a species which requires changing all frequencies.

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20
Q

How are new alleles formed

A

by mutations

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21
Q

When can sufficient genetic change cause

A

new species to emerge

22
Q

how can speciation due to divergence of isolated populations occur

A

abruptly (instantaneously in the case of polyploidy

gradually model known as gradualism

punctuated equilibrium - short periods of rapid evolution during long periods of little change

23
Q

What is gradualism

A

occurs when major changes are the cumulative product of slow but continuous minor changes. In this model, mutation or immigration occasionally introduces new alleles to the gene pool, which are then acted on by natural selection becoming more common or disappearing.

24
Q

What happens in each generation during gradualism

A

allelic shifts are subtle but tend to increase the frequencies of any advantageous alleles

individuals with the helpful trait survive and reproduce to pass on these alleles both to the next generation

25
Q

What happens over long periods of time in gradualism

A

the cumulative changes in alleles become increasingly visible in the form of phenotypic changes in the population.

26
Q

What is evolution by gradualism like?

A

smooth and continuous process

27
Q

Example of gradualism

A

two populations of the same species may be in two different environments, perhaps only one area contains a particular predator or food source, alleles available that help will avoid the predator and become more common in the population. At some point, the gene pools of the two populations will be so different that, even if reunited, members of the two populations will be so different that, even if reunited, members of the two species will be unable to produce fertile offspring.

28
Q

What does the theory of gradualism explain

A

explains some but not al evolutionary transitions documented in the fossil record

29
Q

What is punctuated equilibrium

A

implies long periods without appreciable change and short periods of rapid evolution

30
Q

What does the fossil record sometimes show

A

long periods of stability with little phenotypic change, at other times, major phenotypic shifts appear rapidly

31
Q

what usually occurs punctuated equilibrium

A

species are generally stable during long periods while stabilizing selection works to maintain the existing phenotype of the species. However,the periods of stability are punctuated by rapid bursts of phenotypic change.

32
Q

What are rapid phenotypic changes are often the result of

A

major upheavals such as long-term climate shifts or the arrival, through immigration or evolution, of new species with a strong ecological impact. During these times of change, natural selection may favor phenotypes that were previously at a disadvantage. Thus stabilizing selection would shift to directional or disruptive selection

33
Q

What is punctuates equilibrium supported by

A

the fossil record, by the gaps that occur between them, eliminated the need for missing links

34
Q

In the punctuated equilibrium models, the ‘sudden’ appearance of a new species in the fossil record implies that:

A

Speciation occurred rapidly in geological time

35
Q

What is polyploidy

A

refers to the presence of more than two complete sets fo chromosomes in a cell. Common policy levels are haploid (n) and diploid (2n), while common polypoid levels are triploid (3n) and tetraploid (4n) but can rarely be as high as hexadecaploid (16n) or more.

36
Q

What can polyploidy cause

A

instantaneous speciation, involves increasing the number of chromosome sets, and usually occurs in plants, which have a much higher tolerance for alternate chromosome numbers than animal

37
Q

What can polypoid be caused by

A

the total non-disjunction of chromosomes during mitosis or most commonly meiosis I.

37
Q

What can polypoid be caused by

A

the total non-disjunction of chromosomes during mitosis or most commonly meiosis I.

38
Q

What happens if a tetraploid individual reproduces with a diploid

A

their offspring will be triploid, they are usually sterile as not all chromosomes have a homologous partner

as a result of this, they can sometimes be considered separate species immediatly

39
Q

When is triploidy useful

A

when seedless quit is denied because since sexual reproduction fails, the embryo-containing seeds no not develop.

For example, commercial bananas and seedless watermelon ae triploid varieties that ae cultivated asexually through cloning.

40
Q

What is polyploidy most frequent in

A

plants but may also occur in animas forexample in frogs

41
Q

What will the chromosome number of polyploid individuals be

A

the multiple of the haploid number

fore example if n = 5, the chromosomes present would be 15, 20, 25…

42
Q

What may result in gene flow

A

Emigration

43
Q

What may result in allopatric speciation?

A

geographical barrier isolates two populations

44
Q

why is polyploidy much more common in plant species?

A

Plants ae capable of self-pollination

45
Q

The proliferation of black or white moths instead of grey moths in regions is an example of:

A

Disruptive selection

46
Q

Males of different species of the fruit fly Bactrocera that live in the same parts of the Fijian Islands have different elaborate courtship rituals. These rituals involve fighting other males. What does this represent

A

Behavioural isolation

47
Q

What suggests that the gaps in the fossil record might be due to mass extinction events?

A

punctuated equilibrium

48
Q

What is the best explanation for the sudden appearance of a new species in the fossil record, according to the concept of punctuated equilibrium?

A

speciation occurred rapidly in geologic time

49
Q

Leopard frogs and wood frogs reach sexual maturity at different times in the spring and hence cannot interbreed. This is an example of:

A

Temporal isolation

Biology (51 decks)

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