Module 6: Evolution

Question 1

Define the term evolution
Evolution occurs due to what?

Answer 1

the change in inherited characteristics of a group of organisms over time

changes in the frequency of different alleles within a population

Question 2

The sum total of all the genes in a population is known as the …

What factor is not linked to the frequency in which an allele occurs in a population?

Answer 2

gene pool

-whether the gene codes for a dominant/recessive characteristic

Question 3

What does the Hardy-Weinberg principle state?

The Hardy-Weinberg principle models what relationship?

Answer 3

that in a stable population with no disturbing factors , the allele frequencies will remain constant from one generation to the next and there will be no evolution

the mathematical relationship between the frequencies of alleles and genotypes in a theoretical population thats stable and not evolving

Question 4

In the Hardy-Weinberg principle , what do the following features represent?

p squared
2pq
q squared

Answer 4

p squared= frequency of homozygous dominant genotype in the population

2pq= frequency of heterozygous genotype in the population

q squared= frequency of homozygous recessive genotype in the population

Question 5

What does the Hardy-Weinberg principle assume about a theoretical breeding population?

5 things

Answer 5

-that the population is large
-that the population is isolated
-that random mating occurs
-no mutations occur
-there are no selection pressures of any type

Question 6

Describe the 5 main factors that can lead to changes in the frequency of alleles within a population and hence affect the rate of evolution

Answer 6

mutations-formation of new alleles leads to genetic variation within the population

sexual selection-leads to an increase in frequency of alleles which code for characteristics that improve mating success

gene flow-movement of alleles between populations

genetic drift-(occurs in small populations) the change in allele frequency due to the random nature of mutation
-appearance of a new allele will have a greater impact on a small population as there is a smaller number of alleles in the gene pool

natural selection-increases the number of individuals that have characteristics that improve chances of survival , reproduction rates of these individuals will increase as will the frequency of alleles coding for these characteristics

Question 7

Changes in environment , presence of new diseases , prey , competitors and human influences are all examples of what?

What can all these things lead to ?

Answer 7

selection pressures

evolution , as the population may adapt to these changing conditions

Question 8

What is meant by a limiting factor?
What are the two types of limiting factor?

Answer 8

a factor which can limit or decrease the size of a population

1)Density dependent limiting factors
2)Density independent limiting factors

Question 9

What are density dependent factors dependent on?
What are some examples? Give 4

Answer 9

the population size
examples include competition , predation , parasitism and communicable disease

Question 10

Do density independent factors affect populations of all sizes in the same way or in different ways?

What are some examples? Give 4

Answer 10

in the same way

examples include climate change , natural disasters , seasonal change and human activity such as deforestation