Topic 4B: Diversity of Life

Question 1

Suggest why antibiotic resistance often evolves in hospitals. [2]

Answer 1

1. More antibiotics used in hospitals;
2. Patients often have weaker immune system, so bacteria divide faster

Question 2

Describe how farming cattle as a source of milk could have led to an increase in the percentage of humans with the LP gene which gives them the ability to continue producing lactase. [4]

Answer 2

1. LP due to mutation;
2. Milk provides glucose;
3. Individuals with LP more likely to survive and reproduce;
4. Directional selection;
5. Frequency of allele increases (in offspring/next generation)

Question 3

What aseptic techniques should be used when investigating the effect of anti microbial substances on microbial growth and why? [3]

Answer 3

1. Wash hands with soap to kill microbes
2. Wear apron to prevent contamination;
3. Burning Bunsen close by to create upward current of air;
4. Disinfect bench to kill microbes;
5. Flame neck of bottle to kill microbes;
6. Sterilise pipette/spreader to kill microbes;
7. Put used pipette tips in disinfectant to kill microbes;
8. Lift lid of plate slightly to prevent entry of microbes

Question 4

A student used a dilution series to investigate the number of cells present in a liquid culture of bacteria.

Describe how he made a 1 in 10 dilution and then used this to make a 1 in 1000 dilution of the original liquid culture of bacteria. [3]

Answer 4

1. Add 1 part (bacteria) culture to 9 parts (sterile) liquid (to make 0.1 dilution);
2. Mix (well);
3. Add 1 part 0.1 (suspension) to 99 parts (sterile) liquid (to make 0.001 dilution)

Question 5

Suggest and explain why farm animals have a higher percentage of bacteria resistant to tetracycline than streptomycin. [2]

Answer 5

1. Tetracycline used more often;
2. Resistant bacteria more likely to (survive and reproduce and) pass on allele for resistance

Question 6

Suggest and explain why the number of bacterium in a culture might be lower if aseptic techniques aren’t used. [2]

Answer 6

1. New microbe (introduced);
2. (these bacteria) use food source

Question 7

In taxonomy, an organism is identified by referring to the species name and the genus name.

What term is used to describe this method of naming organisms? [1]

Answer 7

1. Binomial

Question 8

Describe how organisms are grouped in a phylogenetic classification system. [2]

Answer 8

1. Hierarchy (of groups) with no overlaps;
2. (Grouped) according to evolutionary origins

Question 9

Explain why it is more useful to calculate an index of diversity than to record species richness. [2]

Answer 9

1. (Index of diversity also) measures abundance of each species;
2. (So useful because) may be many of some species

Question 10

Suggest one reason why scientists used biomass instead of the number of individuals of each plant species when collecting data to measure diversity. [1]

Answer 10

1. Too numerous to count individuals
   OR
   Too time consuming
   OR
   Individual organisms could not be identified

Question 11

How could planting hedgerows increase biodiversity? [3]

Answer 11

1. More plant species;
2. (So a) wider variety of food sources available for animals;
3. More habitats are available in the hedgerows

Question 12

Suggest two reasons for conserving rainforests. [2]

Answer 12

1. For biodiversity;
2. Conserve habitats;
3. Reduces climate change;
4. Source of medicines/drugs/wood;
5. Reduces erosion;
6. (For) tourism

Question 13

Farmers are now being encouraged to replant hedges in their land.

Suggest and explain one advantage and one disadvantage to a farmer replanting hedges on his farmland. [2]

Answer 13

Advantage:
1. Greater biodiversity so increase in predators of pests
OR
Increase in predators of pests so more yield
OR
Increase in pollinators so more yield;

Disadvantage:
2. Reduced land area for crop growth
OR
Greater biodiversity so increase pest population
OR
Increase pest population so less yield

Question 14

The index of diversity of insects was higher in a hedge than in a barley field.

Suggest why. [3]

Answer 14

1. Mor plant species;
2. More variety of food;
3. More habitats

Question 15

Define the term genome. [1]

Answer 15

1. The complete set of genes in a cell/organism
   OR
   (All) the DNA in a cell/organism

Question 16

A scientist was given a large number of seeds from a population of trees in the centre of a city and also a large number of seeds from a population of trees in the countryside.

Describe how he should collect and process data from these seeds to investigate whether there is a difference in seed size between these two populations of trees. [5]

Answer 16

1. Use random sample of seeds (from each population);
2. Use large sample to be representative of whole population;
3. Weigh the sample;
4. Calculate a mean and standard deviation (for each population);
5. Use the (Student’s) t-test;
6. Analyse whether there is a significant difference between (the means of) the two populations

Question 17

What data is needed to calculate the index of diversity in a habitat? [1]

Answer 17

1. (Number of species and) number of individuals in each species

Question 18

Give two ways to ensure that the index of diversity is representative of a habitat. [2]

Answer 18

1. Random samples;
2. Large number (of samples)

Question 19

State three comparisons of genetic diversity that scientists use in order to create phylogenic trees. [3]

Answer 19

1. The (base) sequence of DNA;
2. The (base) sequence of mRNA;
3. The amino acid sequence (of proteins)

Question 20

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

Explain why. [2]

Answer 20

1. Closer the (amino acid) sequence the closer the relationship;
2. (Protein structure) related to (DNA) base sequence

Question 21

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

Explain why. [2]

Answer 21

1. More bases than amino acids;
2. Code is degenerate

Question 22

The genetic diversity of species is measured be comparing differences in the base sequence of DNA or differences in the base sequence of mRNA.

Give two other ways in which genetic diversity between species is measured. [2]

Answer 22

1. Comparing (measurable/observable) features/characteristics;
2. Comparing amino sequences/primary structures (of a protein)

Question 23

What is meant by species richness?

Answer 23

1. (A measure of) the number of (different) species in a community

Question 24

Define the term species. [1]

Answer 24

1. (A group of) organisms that are able to produce fertile offspring

Question 25

All the species of field mice in Europe have names starting with Apodemus.

What information does this give about field mice? [2]

Answer 25

1. Same genus;
2. Same evolutionary origin

Question 26

Scientists obtained DNA from otters that were alive before hunting started.

Suggest one source of the DNA. [1]

Answer 26

1. Bone / skin / preserved remains / museums

Question 27

Other than hunting, suggest two reasons why populations might show very low levels of genetic diversity. [2]

Answer 27

1. Population might have started with small number of individuals;
2. Inbreeding

Question 28

Differences in the primary structure of haemoglobin molecules can provide evidence of phylogenetic (evolutionary) relationships between species.

Explain how. [5]

Answer 28

1. Mutations change base sequence;
2. (Causing) change in amino acid sequence;
3. Mutations build up over time;
4. More differences (in amino acid sequence) between distantly related species;
5. Distantly related species have earlier common ancestor

Question 29

What is the difference between between species richness and an index of diversity? [1]

Answer 29

1. Species richness only measure the number of (different) species / does not measure number of individuals if each species

Question 30

The UK government pays farmers to leave grassy strips around the edges of fields. These grassy strips contain a variety of plant species. Leaving the strips is an attempt to encourage biodiversity of animals.

Give two reasons why the grassy strips increase the biodiversity of animals. [2]

Answer 30

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 habitats