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AH biology > U2) KA2) EVOLUTION - by drift and selection > Flashcards

U2) KA2) EVOLUTION - by drift and selection Flashcards

1
Q

what is Evolution

A
  • evolution is the change over time in the proportion of individuals in a population differing in one or more inherited traits
  • the individuals in the population show genetic variation as they carry different versions of inherited traits
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2
Q

variation of traits arises as a result of _____

- what is this ?

A
  • mutation
  • mutation is a change in the DNA sequence
  • different versions of inherited traits have different DNA base sequences as a result of genetic mutation
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3
Q

what is a novel allele

A

if a mutation results in a base sequence which codes for a different amino acid in a polypeptide , then the mutation has produced a novel allele

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4
Q

what are the three possible effects of mutations on evolutionary fitness of an individual

A
  • a large number of mutations are neutral because there is no effect on the evolutionary fitness of an individual
  • some mutations are harmful , because they reduce the individuals fitness
  • very rarely some mutations are beneficial to the fitness of the individual
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5
Q

most mutations are ______ or ______, but in rare cases they may be ________ to the fitness of an individual

A
  • deleterious , neutral

- advantageous

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6
Q

what can cause evolution

how ?

A

evolution can occur through

  • the random process of genetic drift
  • the non random process of natural selection and sexual selection
  • they can cause evolution as all of these mechanisms cause changes to the frequency of inherited traits in a population (allele frequency)
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7
Q

what is genetic drift

A
  • genetic drift is the random increase or decrease in frequency of inherited traits over a number of generations
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8
Q

when does genetic drift occur

A

genetic drift occurs when chance events cause unpredictable fluctuations in allele frequencies from one generation to the next
- certain alleles may be under represented or over represented following drift because the new population only carries a random sample of the original populations alleles

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9
Q

what are two common occurring examples of the effects of genetic drift

A
  • population bottlenecks

- founder effect

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10
Q

population bottleneck

A
  • occurs when a population size is randomly reduced for at least a generation , so lowering range of alleles upon which any selection pressure may then act on
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11
Q

founder effect

A
  • a few members of the population are isolated from the larger population , the gene pool of the new population is not representative of the original one
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12
Q

why does genetic drift have greater effect in small populations

A
  • alleles are more likely to be completely lost by chance from a small gene pool
  • any change in allele frequency is likely to be more significant to the population as a whole
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13
Q

gene pool

A

the stock of different genes in an interbreeding population

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14
Q

a gene pool is altered by genetic drift . explain

A

a gene pool is altered by genetic drift because certain alleles may be under represented or over represented

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15
Q

genetic variation

A

Genetic variation is the difference in DNA among individuals or the differences between populations.

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16
Q

variation in traits rises as a result of _____

A

mutation

17
Q

natural selection acts on _____ ______ in populations

A

genetic variation

18
Q

what is natural selection

A
  • a non random process which selects individuals based on their survival chances and thus increases their chances of passing on their inherited genes
19
Q

what does selection result in

A
  • results in the non random increase in the frequency of advantageous alleles and the non random decrease in the frequency of deleterious alleles(alleles which reduce fitness)
20
Q

summary of process of natural selection

A
  • population produces more offspring than the environment can support
  • individuals with variations that are best suited to the environment are more likely to survive longer and produce more offspring
  • the alleles for the favoured traits are inherited so they are more likely to become more frequent in subsequent generations
21
Q

what is sexual selection

differentiate this from natural selection

A

sexual selection is the non random increase in the frequency of alleles that make mating and reproduction more likely
- sounds similar to natural selection, however , the selected alleles do not increase survival chances

22
Q

sexual selection is thought to be more important in habitats where food is abundant and predation is low. why?

A

the selected alleles don’t necessarily help in the general survival of the individual in terms of obtaining food or avoiding predators.

23
Q

sexual selection may lead to sexual ______

A

sexual dimorphism

24
Q

what is sexual dimorphism

A
  • sexual dimorphism means there are differences in characteristics between two sexes of the same species (other than their sex organs)
  • both genders have distinct differences
  • so that the fenale will select the male with the most desirable charatersitucs
25
Q

sexual dimorphism - what do differences in gender include

A
  • differences in terms of size and colour

- in most cases of sd , the male is larger / heavier armoured/ has more conspicuous markings /structures / behaviours

26
Q

what is reversed sexual dimorphism - give an example

A
  • some species of bird have reversed sexual dimorphism , where the female is larger / more bright coloured
  • in many species of bird the female is larger- the male is better adapted for hunting small prey that are suitable for feeding his young nestlings during the breeding season
27
Q

sexual selection can occur through…

A

male-male rivalry

female choice

28
Q

what is male-male rivalry

A
  • in male-male rivalry ,large size or weaponry -such as antlers , tusks, jaws, teeth and horns increase an individuals access to female through successful conflict with competing males
29
Q

what is female choice

A
  • female choice involves the female assessing the fitness of males through observing them : observing honest signals related to display, colour , plumes , calls and songs
  • ‘honest signals’ are characteristics that allow potential mates to asses the genetic quality or fitness of the males
30
Q

what is a selection pressure

- where selection pressures are strong , the rate of evolution can be _____

A
  • selection pressures are the environmental factors that influence which individuals in a population pass on their alleles
  • selection pressures can increase the heritability of beneficial traits and reduces the heritability of harmful traits
  • selection pressures can be biotic(competition, predation, disease, parasitism) or abiotic (temperature, light. humidity, pH, salinity)
  • rapid

AH biology (23 decks)

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