Drift And Selection

Question 1

What is the definition of 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

During evolution what do changes in allele frequency occur through?

Answer 2

The non random process of natural selection and sexual selection, and the random process of genetic drift

Question 3

What does natural selection act on?

Answer 3

Genetic variation in population

Question 4

When does variation in traits arise?

Answer 4

As a result of mutation.

Question 5

What is mutation the original source of?

Answer 5

New sequences of DNA

Question 6

What can new sequences of DNA be?

Answer 6

Novel alleles

Question 7

How can mutations affect the fitness of an individual?

Answer 7

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

Question 8

What is an example of a neutral mutation?

Answer 8

Widows peak

Question 9

What is an example of a harmful mutation?

Answer 9

Sickle cell anaemia

Question 10

What is an example of a beneficial mutation?

Answer 10

Antibiotic resistance in bacteria

Question 11

What do populations that produce more offspring than the environment can support result in?

Answer 11

Selection pressures

Question 12

What do individuals with variations that are better suited to their environment tend to do?

Answer 12

They tend to survive longer and produce more offspring, breeding to pass on those alleles that conferred an advantage to the next generation

Question 13

What does selection result in?

Answer 13

The non-random selection increases in the frequency of advantageous alleles and the non random decrease in the frequency of deleterious alleles

Question 14

What is sexual selection?

Answer 14

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

Question 15

What may sexual selection lead to?

Answer 15

Sexual dimorphism

Question 16

What is sexual dimorphism?

Answer 16

Where two sexes of the same species exibit different characteristics e.g. Lions, peacocks ect.

Question 17

What can sexual selection be due to?

Answer 17

Male-male rivalry and female choice

Question 18

What is male-male rivalry?

Answer 18

Large size or weaponry increases access to females through conflict e.g. male deer use antlers to compete for females

Question 19

What is female choice?

Answer 19

involves females assessing the fitness of males. This may result in males attempting to “attract” elaborate displays

Question 20

When does genetic drift occur?

Answer 20

It occurs when chance events cause unpredictable fluctuations in allele frequencies from one generation to the next

Question 21

In what type of population is genetic drift more important and why?

Answer 21

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

Question 22

What can genetic drift occur because of?

Answer 22

The bottleneck and founder effects

Question 23

What is the bottle neck effect?

Answer 23

The population bottleneck effect occurs when a population size is reduced for at least one generation

Question 24

What is the founder effect?

Answer 24

The founder effect occurs through the isolation of a few member of a population from a larger population. The gene pool of the new population is not representative of that in the original gene pool

Question 25

What is a gene pool altered by?

Answer 25

A genetic drift because certain alleles may be under-represented or over-represented and allele frequencies change

Question 26

What happens where selection pressures are strong?

Answer 26

The rate of evolution can be rapid. These selection pressures are the environmental factors that influence which individuals in a population pass on their alleles and they can be biotic or abiotic

Question 27

What are examples of biotic factors?

Answer 27

-competition
-predation
-disease
-parasitism

Question 28

What are examples of abiotic factors?

Answer 28

-changes in temperature
-changes in light
-changes in humidity
-changes in pH
-changes in salinity

Question 29

What does the Hardy-Wineberg (HW) principle state?

Answer 29

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

Question 30

What are the conditions for maintaining the HW equilibrium?

Answer 30

-no natural selection
-random mating
-no mutation
-large population size
-no gene flow (through imigration, in or out)

Question 31

What can the HW principle be used to determine?

Answer 31

Whether a change in allele frequency is occurring in a population over time. Changes suggest evolution occurring

Question 32

What are the HW formulas?

Answer 32

p^2 + 2pq + q^2 = 1 (use when given Q about genotype)

p + q = 1 (use in Q of frequency of alleles)

-p=frequency of dominant alleles- f(A)
-q=frequency of recessive alleles- f(a)
-p^2=frequency of homozygous dominant genotype (individuals)- f(AA)
-2pq=frequency of heterozygous genotype- f(Aa)
-q^2=frequency of homozygous recessive genotype (individuals)- f(aa)