2.4: Variation and evolution

Question 1

What is variation?

Answer 1

The differences between organisms of the same species

Question 2

What are the two types of variation?

Answer 2

Discontinuous and continuous.

Question 3

What’s discontinuous variation?

Answer 3

The differences between individuals of a species where the differences are qualitative (categoric).
It is not impacted by the environment

Question 4

What are examples of discontinuous variation?

Answer 4

Eye colour and blood type.

Question 5

What’s continuous variation?

Answer 5

The differences between individuals of a species where the differences are quantitative (measurable).
Can be impacted by the environment

Question 6

What are examples of continuous variation?

Answer 6

Height and weight.

Question 7

What would you call a characteristic controlled by single genes?

Answer 7

Monogenic.

Question 8

What would you call characteristics controlled by many genes?

Answer 8

Polygenic.

Question 9

What are the two types of competition?

Answer 9

Inter-specific and intra-specific.

Question 10

What is inter-specific competition?

Answer 10

Competition that occurs between individuals of different species competing for the same resources.

Question 11

What is intra-specific competition?

Answer 11

Competition that occurs between individuals of the same species

Question 12

What is selection pressure?

Answer 12

It is an environmental factor that can alter the frequency of alleles in a population, when it is limiting.

Question 13

What is natural selection?

Answer 13

The increased chance of survival and reproduction of organisms with phenotypes suited to their environment.

Question 14

How do advantageous alleles get passed on?

Answer 14

Offsprings that receive the advantageous allele is more likely to survive which means it can breed and pass down it’s genes.

Question 15

What is a gene pool?

Answer 15

The total of all the alleles of all the genes in a population at a given time.

Question 16

What is an allele frequency?

Answer 16

The measure of how often a particular allele (a variant form of a gene) appears in a population

Question 17

What is genetic drift?

Answer 17

The change in frequency of an existing gene variant in the population due to random chance.

Question 18

What is the Hardy-Weinberg principle?

Answer 18

The Hardy-Weinberg principle states that in ideal conditions, allele and genotype frequencies in a population are constant from generation to generation.

Question 19

What are the 9 conditions under which the Hardy-Weinberg principle operates?

Answer 19

• Organisms are diploid
• The allele frequencies are equal in both sexes
• They reproduce sexually
• Mating is random
• Generations don’t overlap
• The population size is very large
• There is no immigration or emigration
• There is no mutation
• There is no selection

Question 20

What are the Hardy-Weinberg equations?

Answer 20

p + q = 1
p² + 2pq + q² = 1

Question 21

What does the p represent in the Hardy-Weinberg equation?

Answer 21

The frequency of the dominant allele within a population. f(A) = p.

Question 22

What does the q represent in the Hardy-Weinberg equation?

Answer 22

The frequency of the recessive allele within a population. f(a) = p.

Question 23

What is the definition of evolution?

Answer 23

A change in the average phenotype of a population.

Question 24

What is the definition of speciation?

Answer 24

The formation of a new species.

Question 25

What is the founder effect?

Answer 25

the loss of genetic variation when a small group of individuals establishes a new population.

Question 26

What are the three types of natural selection?

Answer 26

Stabilising selection, directional selection and disruptive selection.

Question 27

What is stabilising selection?

Answer 27

It is when the average or intermediate phenotype in a population is favoured, and extreme phenotypes are selected against.

Question 28

What is directional selection?

Answer 28

It is when one extreme phenotype is favoured over both the other extreme and the average phenotype, leading to a gradual shift in the population's genetic makeup.

Question 29

What is disruptive selection?

Answer 29

It is when individuals at both extremes of a trait are favoured while selecting against the intermediate phenotype.

Question 30

What is a species?

Answer 30

A group of phenotypically similar organisms that can interbreed to produce fertile offspring.

Question 31

What is reproductive isolation?

Answer 31

The prevention of reproduction and, therefore, gene flow between breeding groups within a species.

Question 32

What are the two types of reproductive isolation?

Answer 32

Pre-zygotic and post-zygotic

Question 33

What is pre-zygotic isolation?

Answer 33

It is when gametes are prevented from fusing and so a zygote is never formed.

Question 34

What is post-zygotic isolation?

Answer 34

It is when gametes fuse and a zygote forms, resulting in hybrid offspring that are either not viable or infertile.

Question 35

What is a deme?

Answer 35

A small, locally interbreeding group of organisms within a larger population.

Question 36

What is allopatric speciation?

Answer 36

The evolution of new species from demes isolated in different geographical locations.

Question 37

What is sympatric speciation?

Answer 37

The evolution of new species from demes sharing a geographical location.

Question 38

What are examples of sympatric speciation?

Answer 38

Morphological isolation, gametic isolation and seasonal isolation.

Question 39

What is morphological isolation?

Answer 39

A type of reproductive isolation where physical differences between species prevent successful mating and fertilisation.

Question 40

What is gametic isolation?

Answer 40

A pre-zygotic reproductive barrier that prevents different species from interbreeding because their gametes (sperm and eggs) are incompatible.

Question 41

What is seasonal isolation?

Answer 41

It is when species are reproductively isolated due to differences in their breeding or flowering seasons.

Question 42

What’s a hybrid?

Answer 42

The offspring of a cross between members of different species.