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Biology Unit 2 > Evolution > Flashcards

Evolution 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.

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2
Q

During evolution how do the changes in allele frequency occur?

A
  • The non-random processes of natural selection and sexual selection
  • The random process of genetic drift
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3
Q

What effect can mutations have on an organism?

A

Most mutations are harmful or neutral, but in rare cases they may be beneficial to the fitness of an individual.

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4
Q

Describe natural selection

A
  • Population produces more offspring than environment can support.
  • Variation amongst offspring (as a result of mutations)
  • there are selection pressures (e.g. disease, changes in temperature)

-individuals with a selective advantage survive to reproduce and pass on favorable alleles to their offspring

  • those favorable alleles confer an advantage to the next generation and become more frequent.
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5
Q

How do variation in traits arise?

A

As a result of a mutation

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6
Q

Describe the process of Natural Selection

A
  • Population produces more offspring than the environment can support
  • Variation amongst offspring (as a result of Mutations)
  • Selection pressures are imposed e.g. Changes in Temperature, Disease
  • Individuals with a selective advantage survive to reproduce and pass on favourable alleles to their offspring .
  • Those favourable alleles confer an advantage to the next generation and become more frequent.
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7
Q

What does selection result in?

A

The non- random increase in the frequency of advantageous alleles and the non- random decrease in the frequency of deleterious alleles.

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8
Q

What are selection pressures?

A

Environmental factors that influence which individuals in a population pass on their alleles

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9
Q

What are biotic selection pressures?

A
  • Competition, predation, disease, parasitism
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10
Q

What are abiotic selection pressures?

A
  • Changes in temperature, light, humidity, pH, salinity.
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11
Q

What is sexual selection?

A

Involves the selection of alleles that increase the individuals chances of mating and producing offspring.

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12
Q

What determines the allele frequency in sexual selection?

A

The selection of mating partners.

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13
Q

What type of characteristics does sexual selection select?

A

Characteristic that have little survival benefit for the individual, but increase their chances of mating

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14
Q

What can sexual selection lead to?

A
  • sexual dimorphism ( physical differences between males and females of the same species, other than sex organs)
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15
Q

What can cause sexual selection?

A
  • Male- male rivalry
  • Female choice
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16
Q

What is male- male rivalry?

A
  • Large size or weaponry increases
  • access to females through conflict
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17
Q

What does female choice involve?

A

Females assessing the fitness of males

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18
Q
A
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19
Q

When does Genetic drift occur?

A

When chance events cause unpredictable fluctuations in allele frequencies from one generation to the next

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20
Q

When is genetic drift more important?

A

Smaller populations, as alleles are more likely to be lost from the gene pool

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21
Q

When do population bottlenecks occur?

A

When a population size is reduced for at least one generation.

22
Q

When does the founder effect occur?

A

Through the isolation of a few members of a population from a larger population.

23
Q

What can be said about the gene pool of a new population due to the founder effect?

A

The gene pool of the new population is not representative of that in the original gene pool

24
Q

How is a gene pool altered by Genetic Drift?

A

Certain alleles may be under- represented or over-represented and allele frequencies change

25
Q

What are the conditions needed for maintaining the hard Weinberg principle ?

A
  • No natural selection
    -Random mating
  • No mutating
  • Large population size
  • no gene flow ( through migration, in or out)
26
Q

What can the HW principle be used for?

A

To determine whether the change in allele frequency is occurring in a population over time

27
Q

What is fitness an indication of?

A

An indication of an individuals ability to be successful at surviving and reproducing

28
Q

What is fitness a measure of?

A

The tendency of some organisms to produce more surviving offspring than competing members of the same species

29
Q

How do you calculate absolute fitness?

A

Frequency of a particular genotype after selection/ Frequency of a particular genotype before selection

30
Q

How do you calculate relative fitness?

A

Number of surviving offspring/ number of surviving offspring per individual of the most successful genotype

31
Q

What is co - evolution?

A

The process by which two or more species evolve in response to selection pressures imposed by each other

32
Q

What is symbiosis?

A

co-evolved intimate relationships between members of two different species ?

33
Q

What are the type of symbiotic interactions?

A
  • Mutualism
  • commensalism
  • Parasitism
34
Q

What is Mutualism?

A

Both species in the interaction are independent on each other for resources or other services +/ +

35
Q

What is Commensalism?

A

Only one of the species benefits +/0

36
Q

What is Parasitism?

A

The parasite benefits in terms of energy and nutrients and the host is harmed as a result of the loss of resources +/-

37
Q

What does the red queen hypothesis state?

A

In a co-evolutionary relationship, change in the traits of one species can act as a selection pressure on the other species

38
Q

Which hosts have greater fitness?

A

Ones that are able to resist and tolerate parasitism

39
Q

What are the costs of sexual reproduction?

A
  • Males are unable to produce offspring
  • Only half of each parents genome passed onto offspring distributing successful parental genomes
40
Q

What is a benefit of sexual reproduction?

A

It increases genetic variation

41
Q

What is Genetic variation?

A

Provides the raw material for adaptation

42
Q

What will happen if a host reproduces sexually?

A

The genetic variability in their offspring reduces the chances that all will be susceptible to infection by parasites

43
Q

Why can asexual reproduction be a successful reproductive strategy?

A

Whole genomes are passed on from parent to offspring

44
Q

What are the benefits of asexual reproduction?

A

Maintaining the genome in very narrow or stable niches

when recolonising distributed habitats

Offspring can be produced more often and in larger numbers

45
Q
A
45
Q

What is Parthenogenesis?

A

Reproduction from a female gamete without fertilisation e.g. bees

46
Q
A
46
Q

Where is parthenogenesis more common?

A

In cooler climates which are disadvantageous to parasites

Regions of lov

47
Q
A
48
Q
A
48
Q
A

Biology Unit 2 (7 decks)

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