B13 Variation And Evolution

Question 1

Natural Selection Step 1 - Variation

Answer 1

There is always variation in a population due to mutation - lots of different alleles.
This leads to a range of different phenotypes.
These differences may be very slight.

Question 2

Natural Selection Step 2 - Competition

Answer 2

Individuals within a pollution complete for a range of things: food, mates, shelter, water, escape from predators.

Question 3

Natural Selection Step 3 - Survival of the fittest

Answer 3

Individuals whose genes give them the ‘best’ characteristics are more likely to be the best competitors.

Question 4

Natural Selection Step 4 - Reproduction/inheritance

Answer 4

Individuals who reproduce are likely to pass on these specific beneficial genes.

Question 5

Geneic engineering

Answer 5

This is a technique where a gene can be taken from one organism and placed into another to give a desired characteristic. The organism is now said to be transgenic.

Question 6

Genetically modified crops

Answer 6

• Genetically modified crops include plants that are resistant to attack by insects because they have been modified to make their own pesticide. This means that more of the crops survive to provide food for people.
• GM plants that are more resistant than usual to herbicides mean farmers can spray and kill weeds more effectively without damaging their crops. Again, this increases the crop yield.
• Rice plants have been modified to withstand being completely covered in water for up to three weeks and still produce a good crop. This can save lives as 3.3 billion people rely on rice for their main food, and severe flooding in many rice growing countries is becoming more common.

Question 7

Transferring genes to animal and plant cells:

Answer 7

• Genes from jellyfish have been transferred to crops so that they glow in the dark when lacking water. This is useful because it shows where irrigation is most needed. This can help reduce water wastage.
• Mice have been modified to model human diseases including Alzheimer’s, cancer, and diabetes. This helps scientists learn more about the diseases and test treatments.

Question 8

Key steps in genetic engineering

Answer 8

Step 1- A cell is removed from the pancreas of a human (this is where insulin is produced so the gene will be actively producing insulin).

Step 2- The gene responsible for producing insulin is identified and cut out using enzymes.

Step 3- The human gene is transferred to the plasmid (the vector) taken from a bacterial cell.

Step 4- The bacterial DNA (which now contains the human gene for making insulin) is put back into the bacteria cell.

Step 5- The bacteria is encouraged to divide.
As it does this, it produces the human insulin which can then be collected. It us usually transferred at an early stage of development so it develops with the desired characteristics.