Populations and evolution - Yr 2

Question 1

Hardy Weinberg Principle

Answer 1

The principle predicts that the proportion of dominant and recessive alleles of any gene in a population remains the same from one generation to next provided five conditions: No mutations, population is isolated, no natural selection (alleles are equally likely to be passed on), large population, mating is random

Question 2

Gene Pool

Answer 2

all the different alleles of all the genes of all the individuals in a population at any one time

Question 3

Allelic frequency

Answer 3

the number of times an allele occurs within the gene pool in a population, relative to all others at same locus

Question 4

Discontinuous variation

Answer 4

Distinct forms with no intermediate types.

Question 5

Continuous variation

Answer 5

No distinct categories – likely to obtain a bell-shaped curve known as a normal distribution curve.

Question 6

Natural selection

Answer 6

Darwin’s theory to explain the mechanism of evolution. The process by which organisms better adapted to their environment survive and reproduce and pass on their advantageous alleles to the their offspring, whilst those less well adapted fail to do so.

Question 7

Directional selection

Answer 7

Favours one extreme of the range of characteristics and the other extreme is selected against – shift in population curve

Question 8

Stabilising selection

Answer 8

Favours the mean of the distribution because the extremes are at a selective disadvantage – frequency of mean phenotype increases

Question 9

Disruptive selection

Answer 9

Favours both extremes of a distribution, selection occurs against the mean – results in bimodal distribution.

Question 10

Genetic Drift

Answer 10

Causes random changes in allele frequencies in a population due solely to chance factors.

Question 11

Genetic bottleneck

Answer 11

Severe reduction in population size

Question 12

Founder effect

Answer 12

Isolation of a small group of individuals by migration or a physical barrier.

Question 13

Speciation

Answer 13

Evolution of new species from existing ones. Process by which reproductive isolation occurs between two populations so that they evolve along their own separate paths into 2 separate species with different allele frequencies.

Question 14

Species

Answer 14

A group of organisms that have a common ancestry and so share the same genes and are capable of breeding together to produce fertile offspring - are reproductively separated from other species.

Question 15

Allopatric speciation

Answer 15

occurs when populations occupy different environments – they are geographically separated.

Question 16

Sympatric speciation

Answer 16

occurs when populations are reproductively isolated within the same environment.