Unit 2: Key Area 2 - Evolution Flashcards

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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

Describe the process of evolution

A

During evolution, changes in allele frequency occur through the non-random processes of natural selection and sexual selection, and the random process of genetic drift

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3
Q

What does natural selection act on and how does it arise

A

Natural selection acts on genetic variation in populations. Variation in traits arises as a result of mutation.

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4
Q

Describe how mutations give rise to genetic variation

A

Mutation is the original source of new sequences of DNA. These new sequences can be novel alleles. Most mutations are harmful or neutral, but in rare cases they may be beneficial to the fitness of an individual.

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5
Q

What happens during natural selection

A

During natural selection, the populations produce more offspring than the environment can support

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6
Q

Describe the process of natural selection

A

Individuals with variations that are better suited to their environment tend to survive longer and produce more offspring, breeding to pass on those alleles that conferred an advantage to the next generation

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7
Q

What does selection result in

A

Selection results in 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

Describe sexual selection

A

Sexual selection is the non-random process involving the selection of alleles that increase the individual’s chances of mating and producing offspring

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9
Q

What may sexual selection lead to

A

Sexual selection may lead to sexual dimorphism

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10
Q

What can sexual selection be a result of

A

Sexual selection can be due to male-male rivalry and female choice

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11
Q

Describe male to male rivalry

A

Male-male rivalry involves large size or weaponry. Increases access to females through conflict.

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12
Q

What is sexual dimorphism

A

Sexual dimorphism is when the male and female of a species look different

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13
Q

Describe female choice

A

Female choice involves females assessing the fitness of males.

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14
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

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15
Q

Why is genetic drift more important in small populations

A

Genetic drift is more important in small populations, as alleles are more likely to be lost from the gene pool

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16
Q

When does population bottleneck occur

A

Population bottlenecks occur when a population size is reduced for at least one generation.

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17
Q

Describe the founder effects

A

Founder effects occur through the isolation of a few members of a population from a larger population. The gene pool of the new population is not representative of that in the original gene pool.

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18
Q

Why is the gene pool altered by genetic drift

A

A gene pool is altered by genetic drift because certain alleles may be underrepresented or over-represented and allele frequencies change

19
Q

What happens when selection pressures are strong

A

Where selection pressures are strong, the rate of evolution can be rapid

20
Q

What are selection pressures

A

Selection pressures are the environmental factors that influence which individuals in a population pass on their alleles.

21
Q

Name the two types of selection pressures and give examples for each type

A

Biotic:

  • competition
  • predation
  • disease
  • parasitism
Abiotic:
Changes in
- temperature
- light
- humidity
- pH
- salinity
22
Q

What does the Hardy - Weinberg (HW) principle state

A

The Hardy-Weinberg (HW) principle states that, in the absence of evolutionary influences, allele and genotype frequencies in a population will remain constant over the generations

23
Q

What are the conditions for maintaining the HW equilibrium

A

The conditions for maintaining the HW equilibrium are: no natural selection, no random mating, no mutation, large population size and no gene flow (through migration, in or out).

24
Q

What is the HW principle used to determine

A

The HW principle can be used to determine whether a change in allele frequency is occurring in a population over time

25
Q

What is the HW principle used to calculate

A

Use the HW principle to calculate allele, genotype and phenotype frequencies in populations.

26
Q

What does it mean if there is a change in allele frequency

A

If there is a change in allele frequency it suggests evolution is occurring

27
Q

What is the formula for the calculation of the HW principle

A

p2 + 2pq + q2 = 1

28
Q

What does p, q, p2, 2pq and q2 stand for

A
p = frequency of dominant allele
q = frequency of recessive allele
p2 = frequency of homozygous dominant genotype
2pq = frequency of heterozygous genotype
q2 = frequency of homozygous recessive genotype
29
Q

What is fitness an indication of

A

Fitness is an indication of an individual’s ability to be successful at surviving and reproducing

30
Q

What is fitness a measure of

A

Fitness is a measure of the tendency of some organisms to produce more surviving offspring than competing members of the same species.

31
Q

What does fitness refer to

A

It refers to the contribution made to the gene pool of the next generation by individual genotypes

32
Q

What can fitness be defined as

A

Fitness can be defined in absolute or relative terms

33
Q

Describe absolute fitness

A

Absolute fitness is the ratio between the frequency of individuals of a particular genotype after selection, to those before selection

34
Q

How to calculate absolute fitness

A

frequency of a particular genotype after selection

/ frequency of a particular genotype before selection

35
Q

What does the value of absolute fitness mean if

a) it is 1
b) it is greater than 1
c) it is less than 1

A

a) If the absolute fitness is 1, then the frequency of that genotype is stable.
b) A value greater than 1 conveys an increase in the genotype
c) and a value less than 1 conveys a decrease in the genotype

36
Q

Describe relative fitness

A

Relative fitness is the ratio of the number of surviving offspring per individual of a particular genotype to the number of surviving offspring per individual of the most successful genotype

37
Q

How to calculate relative fitness

A

number of surviving offspring per individual of a particular genotype
/ number of surviving offspring per individual of the most successful genotype

38
Q

What is Co-evolution

A

Co-evolution is the process by which two or more species evolve in response to selection pressures imposed by each other

39
Q

What does the change in the trait of one species act like on other species

A

A change in the traits of one species acts as a selection pressure on the other species

40
Q

Where is co evolution usually seen and what impacts do they usually have

A

Co-evolution is frequently seen in pairs of species that have symbiotic interactions
The impacts of these relationships can be positive (+), negative (-) or neutral (0) for the individuals involved

41
Q

Describe Mutualism

A

Mutualism: both organisms in the interaction
are interdependent on each other for
resources or other services. As both
organisms gain from the relationship, the
interaction is (+/+)

42
Q

Describe Commensalism

A

Commensalism: only one of the organisms benefits (+/0)

43
Q

Describe Parasitism

A

Parasitism: the parasite benefits in terms of energy or nutrients and the host is harmed as the result of the loss of these resources (+/-).

44
Q

What does the Red Queen hypothesis state and what does this mean

A

The Red Queen hypothesis states that, in a co-evolutionary relationship, change in the traits of one species can act as a selection pressure on the other species
This means that species in these relationships must adapt to avoid extinction