7B Populations and Evolution

Question 1

Species

Answer 1

A group of similar organisms that can reproduce to give fertile offspring

Question 2

Population

Answer 2

A group of organisms of the same species living in a particular area at a particular time so they have the potential to interbreed

Question 3

Gene Pool

Answer 3

The complete range of alleles present in a population

Question 4

What are the conditions where the Hardy Weinberg principle is true?

Answer 4

Large population with no immigration, emigration or mutations
Random mating

Question 5

What is the Hardy Weinberg equation for allele frequency?

Answer 5

p + q + 1

Question 6

What is the Hardy Weinberg equation for the genotype frequency?

Answer 6

p2 + 2pq + q2 = 1

Question 7

What are the uses of the Hardy Weinberg principle?

Answer 7

Predicting allele frequency, predicting genotype frequency, predicting the percentage of the population that has a certain genotype, showing if any external factors are affecting allele frequency

Question 8

Variation

Answer 8

The differences that exist between individuals

Question 9

Intraspecific variation

Answer 9

Variation within a species

Question 10

Selection pressures

Answer 10

Pressures that affect an organism’s chance of surviving, e.g weather, disease and competition

Question 11

Stabilising selection

Answer 11

Individuals with characteristics towards the middle of the range are more likely to survive and reproduce, e.g fur length

Question 12

Directional selection

Answer 12

Individuals with alleles for a single extreme phenotype are more likely to survive and reproduce, e.g how fast an animal can run

Question 13

Disruptive selection

Answer 13

Individuals with alleles for either extreme phenotype are more likely to survive and reproduce, e.g beak size- small beaks small seeds, large beaks large seeds

Question 14

Speciation

Answer 14

The development of a new species from an existing species, when populations of the same species become reproductively separated

Question 15

Allopatric speciation

Answer 15

Geographically separated so will experience slightly different conditions. Different alleles will be advantageous so natural selection occurs

Question 16

How do you know when you’ve made a new species?

Answer 16

They will be unable to produce fertile offspring

Question 17

Sympatric speciation

Answer 17

Random mutations within a population prevent individuals that carry the mutation from breeding with other members of the population that don’t carry the mutation

Question 18

How does reproductive isolation occur?

Answer 18

Seasonal changes (mating seasons change so they are sexually active at different times in the year)
Mechanical changes (Changes in size, shape or function of genitalia 
Behavioural changes (a group of individuals may develop different courtship rituals)

Question 19

Genetic drift

Answer 19

An allele becomes more common in a population due to chance

Question 20

How can genetic drift lead to evolution?

Answer 20

Individuals within a population show variation in their genotypes
By chance, a certain allele is passed on more to offspring than others, so the number of organisms with a certain allele increases
By chance the same allele is passed on again and again it becomes more common in the population

Question 21

What causes evolution?

Answer 21

Natural selection and genetic drift