genetic diversity/ biodiversity

Question 1

Scientists can use protein structure to investigate the evolutionary relationships between different species. Explain why.
___________________________________________________________________

Answer 1

1. Closer the (amino acid) sequence the closer the relationship;
2. (Protein structure) related to (DNA) base / triplet sequence;
   Amino acid sequence is related to (DNA) base / triplet sequence = two marks;

Question 2

Comparing the base sequence of genes provides more evolutionary information than comparing the structure of proteins. Explain why

Answer 2

1. Reference to base triplets / triplet code / more bases than amino acids / longer base sequence than amino acid sequence;
   Different (base) triplets code for same amino acids = 2 marks;
   Degeneracy of triplet code = 2 marks
2. Introns / non-coding DNA / degeneracy of code / more than one code for each amino acid;
   Ignore reference

Question 3

A hedgerow is a line of shrubs and trees bordering a field, together with the herbaceous plants at their base. In the last 50 years farmers have removed many hedgerows.
(a) Explain two advantages for a farmer of removing hedgerows.

Answer 3

source of pests / animals, and effect on crop;
source of weeds / no longer taking nutrients, hence competition /
reduced yield; creation of larger fields / leaving room,
hence more efficient use of machinery / grow more crops;
hedgerows have to be maintained, so removal saves time / money;

Question 4

In recent years some hedgerows have been replanted. Ground beetles, which are unable to fly, are predators of crop pests. The beetles overwinter in the shelter of grasses at the base of the hedgerow. In some large fields, a permanent strip of grass is left as shown in the diagram.

Suggest and explain the advantage of leaving the strip of grass in the middle of the field.

Answer 4

allows beetles to remain / survive / over winter in the middle of the
field / strip of grass;
effect on distribution, e.g. do not normally reach the centre of the field
/ can reach all parts;

Question 5

Apart from providing a habitat for predators of crop pests, give two biological benefits of replanting hedgerows.

Answer 5

increases biodiversity;
source of food for animals;
habitat / nest for animals;
reduce need for insecticides / attracts insects away from crop;
windbreaks / prevent erosion / run-off / leaching;
migratory corridors

Question 6

Outline a method the ecologists could have used to determine the plant species richness at one site.

Answer 6

A method of selecting sampling sites at random;
2. Use of quadrat;
3. Identify (plant) species (at site / in each quadrat)
OR
Count number of (different plant) species (at site / in each quadrat);
1. E.g. grid with coordinates selected using random

Question 7

.
A student investigated the effect of three types of disinfectant on the growth of Lactobacillus bacteria.
During the investigation, the student:
•   boiled the agar before pouring the agar plates
•   transferred 0.5 cm3 of a diluted liquid culture of Lactobacillus onto each agar plate
•   left some agar plates as controls
•   added to other agar plates different concentrations of the disinfectants as shown in the table in part (a).
After 2 days, she counted the number of colonies of bacteria on each agar plate.
(a) Explain the purpose of:
boiling the agar

b)Transferring the same volume of liquid culture onto each agar plate

Answer 7

1. So no contamination / other bacteria;

2. So same number of bacteria transferred to allow comparison

Question 8

An order is a taxonomic group. All seals belong to the same order. Name one other taxonomic group to which all seals belong.

Answer 8

) Kingdom / phylum / class;

Question 9

what is genetic diversity?

Answer 9

) Difference in DNA / base sequence / alleles / genes;

Question 10

what’s the difference between species richness and index of diversity?

Answer 10

) Species richness measures only number of (different) species / does not measure number of individuals

Question 11

) The traps in the canopy were set at 16–27 m above ground level. Suggest why there was such great variation in the height of the traps.

Answer 11

Trees vary in height.

Question 12

The UK government pays farmers to leave grassy strips around the edges of fields of crops. These grassy strips contain a variety of plant species. Leaving the strips is an attempt to encourage biodiversity of animals.
(a) Give two reasons why the grassy strips increase the biodiversity of animals

Answer 12

1. Increase in plant diversity leads to more types of food for animals;
2. Increase in variety of animals leads to increase in predator species;
3. Increase in niche / habitat