The Theory of Natural Selectionvvv

Question 1

Genetic variation exists within populations due to the presence of different alleles

There is differential reproductive success between the organisms with different alleles of the same gene

Under certain environmental conditions, individuals with certain alleles will have an increased chance of survival and reproduction

New alleles can arise in populations through

Answer 1

random mutation

Question 2

Natural selection can cause the …………of alleles in a population to change over time

Answer 2

frequency

Question 3

Random mutation can produce new alleles of a gene
Many mutations are harmful or neutral but, under certain environmental conditions, the new alleles may benefit their possessor, leading to an increased chance of survival and increased reproductive success

The advantageous allele is passed onto the next generation

As a result, over several generations, the new allele will ……….. over population

Answer 3

increase in frequency in the population

Question 4

Example of Natural selection in Rabbits
Variation in fur colour exists within rabbit populations

At a single gene locus, normal brown fur is produced by a dominant allele whereas white fur is produced by a recessive allele in a homozygous individual

Rabbits have natural predators like foxes which act as a selection pressure

Rabbits with a white coat do not camouflage as well as rabbits with brown fur, meaning predators are more likely to see white rabbits when hunting

As a result, rabbits with white fur are less likely to survive than rabbits with brown fur

Therefore, the rabbits with brown fur have a selection advantage, so they are more likely to survive to reproductive age and be able to pass on their alleles to their offspring

Over many generations, the frequency of alleles for brown fur will increase and the frequency of alleles for white fur will decrease

Question 5

Natural selection causes a change in allele frequencies over time

Selection pressures (caused by the environment an organism is in) increase the likelihood that certain individuals with specific alleles will

Answer 5

survive to reproductive age, enabling them to pass on their alleles to their offspring

Question 6

There are other factors or processes that can affect allele frequencies in a population

Answer 6

The founder effect
Genetic drift
The bottleneck effect