4.3.1 Classification and Evolution – Natural selection and Evolution

Question 1

What is an allele?

Answer 1

An alternative version of a gene.

Question 2

Natural selection is comprised of several detailed steps; describe the process of natural selection.

Answer 2

1. Mutation creates alternative versions of a gene (alleles).
2. This creates genetic variation between the individuals of a species (intraspecific variation).
3. Once variety exists, then the environment can select.
4. If resources are scarce, the environment will select those alleles that give an advantage.
5. This is called a selection pressure.
6. Individuals with an advantageous allele will survive and reproduce.
7. Therefore, they pass on their advantageous allele (inheritance).
8. The next generation will have a higher proportion of individuals with the favourable allele.
9. Over time, the group of organism becomes well adapted to its environment (adaptation).

Question 3

During natural selection what happens to the frequency of disadvantageous alleles?

Answer 3

The proportion of disadvantageous alleles decreases as they are selected against (not as well adapted).

Question 4

What is a good example of natural selection that can be seen in a reduced time frame?

Answer 4

The development of resistance to antibiotics by bacteria.

Question 5

How does penicillin kill bacteria?

Answer 5

Penicillin prevents cell wall formation in bacteria.

Question 6

In a bacteria population of staphylococcus, some may be naturally resistant. What makes these individuals resistant to penicillin?

Answer 6

They produce an enzyme penicillinase which inactivates penicillin.

Question 7

What is one of the major concerns with an increasing population of antibiotic resistant bacteria?

Answer 7

The potential for an epidemic/pandemic.

Question 8

What is the difference between an epidemic and a pandemic?

Answer 8

An epidemic is a disease that affects many people within a community, population, or region. Whereas a pandemic is an epidemic that’s spread over multiple countries or continents.

Question 9

What does MRSA stand for?

Answer 9

Methicillin-resistant staphylococcus aureus

Question 10

What is the issue with developing new antibiotics?

Answer 10

Developing new antibiotics is expensive and takes a long time.

Question 11

Why is the over-use of antibiotics an issue?

Answer 11

By using antibiotics, we change the environment for bacteria. This change the selection pressure by increasing the pressure on bacteria to evolve resistance to them. Resistance can then be transferred between species (via plasmids).