Unit 2: KA2 - Evolution

Question 1

Define the term: evolution.

Answer 1

Evolution is the change over time in the proportion of individuals in a population differing in one or more inherited traits.

Question 2

What happens during evolution?

Answer 2

Changes in allele frequency occur through the non-random processes of natural selection and sexual selection and the random process of genetic drift.

Question 3

How does variation in traits occur?

Answer 3

Mutations

Question 4

What is the source of new/novel sequences of DNA?

Answer 4

Mutation

Question 5

What are the three types of mutation?

Answer 5

• Neutral
• Harmful
• Beneficial

Question 6

Define natural selection.

Answer 6

Natural selection is the non-random increase in frequency of favourable alleles and the decrease of deleterious alleles.

Question 7

Describe the process of natural selection.

Answer 7

• Populations produce more offspring than the environment can support, resulting in selelction pressures.
• Individuals with variations that are better suited to their environment tend to survive longer, so produce more offspring, passing on their advantageous alleles.

Question 8

Define sexual selection

Answer 8

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

Question 9

What is the cause of dimorphism?

Answer 9

Sexual selection.

Question 10

Define dimorphism.

Answer 10

Dimorphism is the difference in characteristics inherited due to sexual selection of alleles.

Question 11

What is the reason for sexual selection?

Answer 11

male-male rivalry or female-choice.

Question 12

Explain the difference between sexual selection and natural selection.

Answer 12

Sexual selection enhances mating success, while natural selection tends to produce well adapted individuals to their environment.

Question 13

When does genetic drift occur?

Answer 13

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

Question 14

Why is genetic drift more important in small populations?

Answer 14

As alleles are more likely to be lost from the gene pool.

Question 15

Name two examples of genetic drift.

Answer 15

• Bottleneck effect

- founder effect

Question 16

Explain the founder effect.

Answer 16

• Isolation of a few member of a population

- gene pool is not representative of original population.

Question 17

How is the gene pool altered by genetic drift?

Answer 17

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

Question 18

Define the term: selection pressures.

Answer 18

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

Question 19

Give examples of biotic selection pressures.

Answer 19

• Competition
• predation
• parasitism
• Disease

Question 20

Give examples of Abiotic selection pressures.

Answer 20

• Temperature
• Light intensity
• Humidity
• pH
• Salinity

Question 21

How do selection pressures’ strength affect evolution rate?

Answer 21

Evolution can be rapid when selection pressures are strong.

Question 22

State the Hardy-Weinberg principle.

Answer 22

In the absence of evolutionary influences, allele and genotype frequencies will remain constant over the generations.

Question 23

What can the H-W principle be used for?

Answer 23

It is used to determine whether a change in allele frequency is occurring in a population over time.

Question 24

What are the five conditions for maintaining the H-W equilibrium.

Answer 24

• No natural selection
• No mutation.
• No gene flow
• Large population size
• Random mating

Question 25

What do changes in allele frequency suggest?

Answer 25

That evolution is occurring.

Question 26

State the H-W equation and the meaning of each variable.

Answer 26

p² + 2pq + q² = 1

• p = Frequency of dominant allele
• q = Frequency of recessive allele
• p² = Frequency of homozygous dominant genotype
• q² = Frequency of homozygous recessive genotype
• 2pq = frequency of heterozygous genotype

Question 27

Define the term: fitness.

Answer 27

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

Question 28

How is fitness measured?

Answer 28

By the tendency of some organisms to produce more surviving offspring than competitors of the same species.

Question 29

Define the two types of fitness.

Answer 29

• Absolute: Ratio between the frequency of individuals of a particular genotype before and after selection.
• Relative: ratio between the number of surviving offspring of a particular genotype and the number of surviving offspring of the most successful genotype.

Question 30

Describe co-evolution.

Answer 30

Co-evolution is the process by which 2 or more species evolve in response to selection pressures imposed by each other.

Question 31

What is the selection pressure in co-evolution?

Answer 31

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

Question 32

What type of relationship is often seen from co-evolved species?

Answer 32

Symbiosis

Question 33

What are the possible effects on organisms in symbiosis?

Answer 33

• Positive (+)
• Negative (-)
• Neutral (0)

Question 34

Name the three types of symbiotic relationships and give their effects on the organisms involved.

Answer 34

• Mutualism: (+/+)
• Commensalism: (+/0)
• Parasitism: (+/-)

Question 35

State the ‘Red Queen Hypothesis’.

Answer 35

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

Question 36

What does the ‘Red Queen Hypothesis’ mean for the species involved?

Answer 36

Species in co-evolutionary relationships must adapt to avoid extinction.