Evolution / Natural Selection

Question 1

Evolution

Answer 1

This is when the frequency of alleles in a population change over time. This occurs by Natural Selection

Question 2

How does Natural Selection happen?

Answer 2

1) Individuals in a population vary due to different alleles. These differences occur by a gene mutation
2) Some individuals are therefore better adapted to their environment
3) Individuals with the advantageous allele will more likely survive and produce offspring with this advantageous allele.
4) Over time this will increase the frequency of this allele in the population or gene pool

Question 3

Species

Answer 3

A group of similar organisms that can reproduce and produce fertile offspring

Question 4

Speciation

Answer 4

The development of a new species

Question 5

How does speciation occur?

Answer 5

When a population becomes reproductively or geographically separated, the gene flow is reduced.
Natural selection then acts on the two populations creating new species over time.

Question 6

Geographical Isolation (Allopatric)

Answer 6

This is when a population is physically isolated due to a barrier. (Allopatric speciation)

• Each population will experience different selection pressures and will change their advantageous alleles to these changes.
• The gene pool of each population will, therefore, become too different and their phenotype will change
• They will become too genetically different and so 2 different species form.

Question 7

Reproductive Isolation

Answer 7

This occurs when mutations in alleles or phenotypes prevent breeding.

• Seasonal changes: Individuals develop different mating seasons
• Mechanical changes: Changes in genitalia prevent successful mating
• Behavioural changes: Different courtships or mating rituals develop that do not attract a mate

Question 8

Sympatric Speciation

Answer 8

This is when random mutations occur that prevent interbreeding and cause seasonal, mechanical and behavioural changes

Question 9

Evidence for Evolution

Answer 9

Molecular biology:

• Genomics: This determines the base sequence of an organism’s genome and the functions of its genes. Scientists can compare DNA and see how closely related organisms are.
• Closely related species have diverged more recently and will have more similar DNA
• Proteomics: This studies the proteins (size, shape, amino sequence) of an organism. Related organisms will have similar DNA and amino acid sequences in their proteins.

Question 10

How is evidence Validated?

Answer 10

The scientific community can:

• Publish articles or journals: They describe their findings here and other scientists can repeat studies.
• Peer Review: Other scientists of this area can validate and study other’s findings.
• Conferences: Scientists can meet and discuss evidence and ask questions to validate the information