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Advanced Higher Biology > Organisms and Evolution - Evolution > Flashcards

Organisms and Evolution - Evolution Flashcards

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1
Q

Define evolution?

A

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

What occurs during evolution?

A

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

Variations in traits arise as a result of what?

A

Mutation

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4
Q

What is mutation the original source of?

A

New sequences of DNA

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5
Q

What are the impact of mutations on organisms?

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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6
Q

What does natural selection act on?

A

Genetic variation in populations

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7
Q

Why does natural selection occur?

A

Populations produce more offspring than the

environment can support

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8
Q

What happens in 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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9
Q

Define sexual selection?

A

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

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10
Q

What does sexual 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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11
Q

What might sexual selection lead to?

A

Sexual dimorphism

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12
Q

What can be the cause of sexual selection?

A

Male-male rivalry and female choice

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13
Q

Define male-male rivalry?

A

Large size or weaponry increases access to females through conflict

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14
Q

Define female choice?

A

Females assessing the fitness of males

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15
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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16
Q

Where is genetic drift more important?

A

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

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17
Q

When do population bottle necks occur?

A

When a population size is reduced for at least one

generation

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18
Q

When do founder effects occur?

A

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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19
Q

What is a gene pool altered by?

A

Genetic drift because certain alleles may be underrepresented or over-represented and allele frequencies change

20
Q

When can the rate of evolution be rapid?

A

Where selection pressures are strong

21
Q

Define selection pressures?

A

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

22
Q

Selection pressures can be biotic or abiotic. Give examples?

A

Biotic:
competition, predation, disease and parasitism

Abiotic:
changes in temperature, light, humidity, pH, salinity

23
Q

What does the Hardy-Weinberg principle state?

A

That in the absence of evolutionary influences, allele and genotype frequencies in a population will remain constant over the generations

24
Q

What are the conditions for maintaining the Hardy-Weinberg equilibrium?

A

No natural selection, random mating, no mutation, large population size and no gene flow (through migration, in or out)

25
Q

What can the Hardy-Weingberg principle be used to determine?

A

Whether a change in allele frequency is occurring in a population over time

26
Q

What is the Hardy-Weinberg formula?

A

p2 + 2pq + q2 = 1

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
27
Q

What is fitness?

A

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

28
Q

Define fitness?

A

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

29
Q

What does fitness refer to?

A

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

30
Q

What are the two types of fitness?

A

Absolute and Relative

31
Q

What is absolute fitness?

A

The ratio between the frequency of individuals of a particular genotype after selection, to those before
selection

32
Q

What is the formula for absolute fitness?

A

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

33
Q

What do the results of the absolute fitness formula show?

A

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

34
Q

What is relative fitness?

A

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

35
Q

What is the formula for relative fitness?

A

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

36
Q

What is co-evolution?

A

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

37
Q

In co-evolution, a change in traits of one species acts as what on the other species?

A

A selection pressure

38
Q

Where is co-evolution frequently seen?

A

In pairs of species that have symbiotic interactions

39
Q

What is symbiosis?

A

Co-evolved intimate relationships between members of two different species

40
Q

What can the impacts of symbiotic relationships be?

A

Positive (+), negative (-) or neutral (0) for the individuals involved

41
Q

What are the three types of symbiotic interactions?

A

Mutualism, commensalism, and parasitism

42
Q

Define mutualism?

A

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 (+/+)

43
Q

Define commensalism?

A

Only one of the organisms benefits (+/0)

44
Q

Define parasitism?

A

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

45
Q

What is the Red Queen Hypothesis?

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

Advanced Higher Biology (10 decks)

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