AQA AS Biology

Topic Questions

4.6 Biodiversity

1a1 mark

Define the term species diversity.

1b2 marks

The statement in Figure 1 below describes two different habitats; ancient woodland  and conifer plantation.

Figure 1

Woodlands that are classed as ancient woodland have been present since 1600 in England or Wales. There is more than one type of ancient woodland, but all contain a complex community of soil microorganisms, accumulations of deadwood, and a range of plant species.


The planting of conifer plantations began after the first world war, and was an attempt to increase forest cover in the UK at this time. They often consist of many coniferous trees of the same species, which drop their acidic needles onto the ground and cast deep shade.

State which of these habitats shows the greatest habitat diversity and explain your answer.

1c2 marks

Some forestry commissions across the UK are attempting to manage plantation woodland differently, taking measures such as felling areas of trees, planting deciduous trees, and installing bird and bat boxes. Suggest two reasons why these measures could increase biodiversity in plantation woodland.

1d1 mark

Suggest why the conifer plantation in Figure 1 is more vulnerable to a changing climate than an ancient woodland.

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2a1 mark

Table 1 below shows the results of pond sampling from two different ponds.

Table 1

Species

Pond A

Pond B

Stonefly nymph

12

1

Caddisfly larva

14

2

Bloodworm

0

25

Mosquito larva

0

53

Freshwater shrimp

15

19

Pond snail

17

3

Calculate the species richness for pond A and pond B in Figure 1.

2b2 marks

The index of diversity for pond B is 2.83. Calculate the index of diversity for pond A.

2c1 mark

Explain why pond B has a higher species richness but a lower index of diversity than pond A.

2d2 marks

The species measured in Table 1 can all be used as ‘indicator species’. This means that their presence or absence can provide information about the quality of the water they live in. Mosquito larvae and bloodworms are known for having a high tolerance for pollution, while mayfly and caddis fly larvae have a very low tolerance for pollution. 

Use the information provided and the results in Table 1 to suggest why there is a difference in diversity index between pond A and pond B. Explain how you reached your conclusion.

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3a3 marks

A group of researchers carried out bird surveys on the same farm over a period of nineteen years. Their results are shown in Table 1 below. 

Table 1

Species

2001

2020

Grey partridge

0

25

Skylark

35

81

Greenfinch

42

4

Goldfinch

0

24

Yellowhammer

2

206

Calculate the increase in the index of diversity between 2001 and 2020 for the results shown in Table 1

3b2 marks

One change in farm management that took place between 2001 and 2020 was that farm hedgerow cutting switched from a yearly cut to a staggered cut every 3 years (each hedgerow cut every 3 years, but not all cut in the same year). State how this could lead to the increase in bird diversity shown in Table 1.

3c1 mark

Suggest what might have caused the decrease in greenfinch numbers between 2001 and 2020 shown in Table 1Do not include the effects of humans illegally catching greenfinches to keep as pets. 

3d2 marks

The research shown in Table 1 above was funded by the RSPB (Royal Society for the Protection of Birds). Figure 2 below shows how the data from Table 1 compares to farm bird data from across England over the same time period.

Figure 2

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Use Figure 2 to suggest why it is so important that the RSPB funds studies such as the one that provided the data for Table 1

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4a1 mark

A scientist wanted to investigate the availability of nectar for pollinators in different types of farmland habitats. They began by sampling the abundance of plants in flower in each of four different habitat types; field margin, hedgerow, pasture and woodland.

State why scientists use sampling to measure abundance rather than measuring the entirety of a site or population.

4b2 marks

The scientist decided to use quadrats to measure the abundance of plants in flower at each sample site. The quadrats were placed at random before the abundance of plants was recorded, and this process was repeated multiple times for each site.

State why it was important that the quadrats were placed at random and that multiple samples were taken.

4c1 mark

Once the scientist had measured the abundance of plants in flower, they were able to convert this into a value for the amount of sugar available for pollinators in each habitat using a table like Table 1 below.

Table 1

Plant species

Mean number of flowers per plant

Nectar sugar content per flower (μg day-1)

Wild garlic

1

865

Lady’s bedstraw

1

1050

Teasel

117.6

4.5

Creeping yellowcress

1

98

State how the ‘mean number of flowers per plant’ would be calculated.

4d2 marks

The scientist's final results are shown in Figure 1 below. 

Figure 1

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The scientist concluded from Figure 1 that modern farming practices must have reduced the number of flowering plants in the field margins and hedgerows, reducing the availability of nectar, and therefore sugar. Give two examples of modern farming practices that might have caused this reduction in flowering plants. 

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5a1 mark

Define the term genetic diversity

5b2 marks

Before the existence of DNA sequencing technology, scientists had to use observable characteristics to estimate genetic diversity in a population. State why DNA sequencing is a more accurate way of measuring this type of diversity than using observable characteristics.

5c2 marks

Table 1 below contains DNA sequences from 4 different species.

Table 1

Species

DNA sequence

A

A C T T C G T C C A A T

B

A C T G G G T C A A T T

C

A C T T C C T C C A T T

D

A G T T G G T C A A T T



  State which of species B-D in Table 1 is most closely related to species A and explain your answer.

5d2 marks

In addition to DNA sequencing, the amino acid sequence of proteins can also be used to determine genetic diversity in groups of organisms. State one advantage and one disadvantage of using protein sequencing rather than DNA sequencing to measure genetic diversity.

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1a3 marks

The traditional practice of coppicing involves repeatedly felling certain species of tree at their base and allowing re-growth over a period of 15-25 years, in order to provide a regular supply of timber. Coppicing yields narrow, straight stems for use in fencing, tool making and construction. Explain one ecological advantage and state one disadvantage of this practice over the felling of mature trees for timber. 

1b4 marks

The numbers of various woodland invertebrates were estimated in two areas of woodland. Area A was an area of coppiced woodland, whereas Area B was an area of fast-growing coniferous woodland plantation managed by the logging industry. Both areas were in the same Northern European country with a temperate climate. Table 1 shows the numbers of each organism counted in the two woodland areas. 

Table 1


Species

Area A

Area B

Coppiced wood

Conifer plantation

Musk beetle

534

0

Shieldbug

89

0

Southern wood ant

674

312

Flat-backed millipede

40

34

Harvestman spider

18

0

Fine-streaked bugkin

12

9

Use the equation provided to calculate the index of diversity (d) in both Area A and Area B in Table 1 and comment on the difference. mq5d
     

1c3 marks

Calculate the species richness of woodland invertebrates from the data shown in Table 1 for Areas A and B. Suggest why this measure of species richness might have limited usefulness in analysing ecological relationships in these two areas. 

1d1 mark

Explain how use of the index of biodiversity adds clarity into the analysis of biodiversity in two contrasting areas like those described in part c), over species richness. 

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2a2 marks

The farming industry has been accused of prioritising productivity over sustainability. Recent initiatives have attempted to restore biodiversity to farms. Outline one such initiative in an arable (crop farming) setting and give the reasons for its expected success. 

2b1 mark

A group of students carried out a comparison between two areas of an agricultural field growing barley. Samples of soil were taken from two areas; (i) directly beneath the barley crop, and (ii) from beneath a 5 m wide field margin around the edge of the barley crop. The soil samples were hand sorted for 30 minutes each and all the animals from the soil were collected and counted. Figure 1 shows the findings. The error bars represent a range of ± 2 standard deviations.

Figure 1

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Explain why an index of diversity would not be able to be quantified from the data in Figure 1

2c4 marks

Using the data provided in Figure 1, assess the effectiveness of the practice of leaving field margins for promoting biodiversity. Outline other investigative work that could provide more information on the effect of field margins on biodiversity. 

2d1 mark

Suggest an explanation for the difference in the number of woodlice observed in Figure 1.

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3a5 marks

Species differences can be measured by using the approaches set out in Table 1

Table 1

The nucleotide sequence of DNA

 

The amino acid sequence of the proteins encoded by DNA and mRNA.

 

The frequency of measurable characteristics

 

The nucleotide sequence of mRNA

 

The frequency of observable characteristics

 

In the table, rank these approaches 1-5 in increasing order of effectiveness, with 1 being the most rudimentary approach and 5 being the most sophisticated. Explain your choice of the rank order. 

3b2 marks

Some students carried out an analysis on the effect of sunlight on the growth of privet leaves on a hedge in the school grounds. Prior to the hedge being cut, they sampled 108 leaves at random from the north-facing side of the hedge and measured the leaves’ lengths. Their data is shown as grouped data in Table 2.

Table 2

Leaf length L / cm

Midpoint / cm

Frequency

Midpoint x frequency

2.0 ≤ L < 2.5

2.25

2

 

2.5 ≤ L < 3.0

2.75

9

 

3.0 ≤ L < 3.5

3.25

14

 

3.5 ≤ L < 4.0

3.75

26

 

4.0 ≤ L < 4.5

4.25

20

 

4.5 ≤ L < 5.0

4.75

11

 

5.0 ≤ L < 5.5

5.25

12

 

5.5 ≤ L < 6.0

5.75

9

 

6.0 ≤ L < 6.5

6.25

5

 

Total

 

108

 

Use the midpoints of each group of leaf lengths to calculate the mean length of the leaves in this sample. Give your answer to 2 significant figures.

3c2 marks

The Human Genome Project was the first piece of research to establish the entire DNA sequence of a human. Explain how DNA sequencing has led to a better understanding of biodiversity. 

3d2 marks

One gene that is often selected for DNA sequencing analysis for comparison of biodiversity is the gene that codes for pyruvate kinase (PKM), an important enzyme in the biochemical pathway glycolysis, which is the first stage of cellular respiration. Suggest why this gene is selected for this purpose. 

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4a1 mark

Read the following passage:

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Deduce a food chain for Yellowstone based on the information contained in the passage.

4b3 marks

Sketch a graph on the axes shown in Figure 1 of the biodiversity index of Yellowstone over time, based on the information in the passage. 

Figure 1

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4c3 marks

Use your knowledge of biodiversity to explain the term ‘unbalanced’ as used in line 10 of the passage provided in part a). Make reference to the changes to biodiversity that you have sketched in part b).

4d3 marks

Some years after the successful introduction of wolves to Yellowstone, biologists examined the genetic diversity of the elk population. They found that the elk population had a more advantageous range of alleles compared to those from the 1980s, prior to the reintroduction of wolves. 

Suggest and explain why this was the case. 

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5a3 marks

Explain why biological sampling of an ecosystem must be free of bias, and how this can be achieved. 

5b5 marks

Figure 1 shows a thistle plant growing in a field periodically grazed by sheep. 

 Figure 1

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A piece of UK upland that has been grazed by sheep has, in the last ten years, been left ungrazed. Design an investigation to estimate the population density of thistle plants that have colonised the area since grazing has been discontinued. Include how your investigation will give a result in thistle plants per hectare (1 hectare (Ha) = 10 000 m2).

5c4 marks

With around 72% of land in the UK being used for agriculture, the role of farming in promoting biodiversity is crucial. In an age when farming productivity has increased substantially, organic farming has emerged as a means of halting the loss of biodiversity. Two techniques, closed-loop farming and rotational silage have been used with some success. Silage is grass or other green plant material, allowed to decay partially and stored in an airtight tank or wrapped in airtight polythene, and used as animal feed during winter. 

Using this information and your knowledge of farming practices, suggest how these two systems might operate. 

5d2 marks

Mob grazing is another farming technique designed to increase biodiversity. In this technique, a whole herd of grazing animals is moved on every few days to another field, allowing the previous grazing area to remain undisturbed for a period of time. Suggest and explain two benefits that this technique could bring to biodiversity. 

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1a2 marks

Compare species diversity with species richness.

1b2 marks

Fertilizers are commonly used today by most farmers as they help to increase crop yield and profit. If it rains shortly after fertilizers are applied to a field then some of the fertilizer can enter nearby water sources as runoff. A conservationist investigated the effect that runoff fertilizer from a nearby farm had on the distribution of organisms living in a stream. At the point where fertilizer had entered the stream, she found a high density of specific organisms but a low index of diversity. 

Suggest how fertilizer contaminating the stream could explain their findings.

1c2 marks

Predict how the index of diversity will change as the conservationist moves further away from the farm to take her sample. Justify your answer.

1d2 marks

The conservationist wanted to use their findings to take action against the local farm. However, the farmer’s lawyer argued that the scientific methods of the conservationist were not rigorous enough to conclude that runoff fertilizer was affecting species richness in the nearby stream.  He demanded that more samples at random locations needed to be taken. 

Explain the importance of taking a large number of samples at random sites. 

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2a2 marks

A biology teacher investigated the different species of insects found in a grassy meadow and in a nearby farmed field. The insects were collected using traps at randomly chosen sites both in the grassy meadow and in the farmed field. Table 1 shows the data collected.

Table 1

Insect species

Number of individuals of each species

Farmed field

Grassy Meadow

Black aphid

230

0

Green aphid

0

569

Dingy Skipper butterfly

0

21

Green Lacewing

7

9

Brown Lacewing

0

37

Total number of organisms of all species

237

646

Use the formula below to calculate the index of diversity for the insects caught in the farmed field.

 bold d equals fraction numerator bold N open parentheses bold N minus 1 close parentheses over denominator stack sum straight n with blank below open parentheses straight n minus 1 close parentheses end fraction

d = index of diversity N = total number of organisms of all species

n = total number of organisms of each species

Show your calculations.

 

Use the formula below to calculate the index of diversity for the insects caught in the farmed field.

2b2 marks

Without doing any further calculations, predict whether the index of diversity for the grassy meadow will be higher or lower than the index of diversity for the farmed field. Explain your answer.

2c2 marks

A student stated that the experiment suggested farming caused a reduction in species diversity. Evaluate this statement.

2d2 marks

Farmers were offered money by an environmental agency to grow more than one plant species in their fields. Very few farmers agreed to this. Suggest why.

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3a1 mark

Describe what is meant by a community.

3b3 marks

Researchers calculated the percentage of reptile species that had gone extinct on five islands in the last 150 years. The islands are made up of sandy beach and forest habitats. The forests have been declining in size over recent years. The researchers calculated the percentage of original forest floor area that remained on each island after 150 years. Figure 1 below shows their results.

Figure 1

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Describe and explain the relationship between the percentage of original forest floor remaining and the percentage of reptile species that have gone extinct.

3c2 marks

What two measurements would the researchers need to obtain in order to calculate the index of diversity of reptiles on each island?

3d2 marks

It was later discovered that some of the reptile species living on the islands with less forest floor remaining had changed scale colour, from green/brown to brown/yellow. Explain how this is an adaptation to their environment.

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4a3 marks

There are ecological, ethical and economic arguments to be made for maintaining biodiversity. Suggest one of each.

4b2 marks

Farmers can plant their crops at different times throughout the year. Traditionally crops were planted in April and harvested in September. However, in modern times farmers have switched to planting their crops in September and harvesting in June/July.

Scientists decided to investigate the effect that the change in planting time had on the number of farmland birds over 10 years. The scientists counted the number of farmland birds found within a 1km radius of farm X that plants its crops in April, and within a 1km radius of farm Y that plants its crops in September.

Figure 1 below shows the data they collected.

Figure 1

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Describe the results seen in Figure 1.

4c3 marks

In recent years, farmers have merged grazing fields together by removing hedgerows.This has resulted in a decline in the diversity of farmland birds. Explain why.

4d2 marks

Organic farms do not use any chemical insecticides. Suggest what effect organic farming would have on the number of farmland birds. Explain your answer.

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5a2 marks

Conservationists investigated the effect of different types of animal grazing on the diversity and number of beetles. Traps were laid and used to measure both the number of different beetle species and the total number of beetles in cow grazed (field type 1), donkey grazed (field type 2) and sheep grazed (field type 3) fields.

Their results are shown in Figure 1 and Figure 2 below.

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State which field is the most species rich. Explain your answer.

5b2 marks

Explain what the standard deviations in Figure 2 suggest about the difference in total number of beetles between the differently grazed fields.

5c3 marks

Suggest three considerations that should have been taken into account when planning the investigation to ensure reliable and fair testing.

5d2 marks

Additional information on the total number of beetle individuals and the number of each beetle species for a cow grazed field (field type 1) is provided in Table 1 below. Calculate the index of diversity for this field using the equation shown.

Table 1

Beetle species

Number of individuals

A

29

B

508

C

47

D

30

E

782

F

11

G

322

H

699

I

38

J

411

K

7

L

86

M

3

N

228

Total

3201

 

straight d equals fraction numerator straight N open parentheses straight N minus 1 close parentheses over denominator sum for blank of straight n open parentheses straight n minus 1 close parentheses end fraction

d = index of diversity N = total number of organisms of all species

n = total number of organisms of each species

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6a2 marks

Corn is a crop plant that produces seeds that are harvested for food. Some students investigated whether corn could be grown successfully using freshwater mixed with seawater. This would reduce the use of freshwater, which can be in short supply in certain countries. Seawater contains dissolved sodium chloride (salt). The students grew corn in plots of equal size in the same area of land. Each plot received one of four watering treatments:

Watering treatment E:

No water

Watering treatment F: 

Freshwater during growth and seed production

Watering treatment G: 

1:1 mix of fresh water and seawater during growth and seed production

Watering treatment H: 

Freshwater during growth and 1:1 mix of fresh water and seawater during seed production 

The students measured the concentration of salt in the soil in each plot and the yield of corn seed harvested from each plot. Their results are shown in Table 1 below:
 

Table 1

 

Treatment

Mean concentration of salt in soil / arbitrary units

Mean yield of corn seed / g

 

E

10.2

345

 

F

9.6

805

 

G

13.6

537

 

H

11.5

696

 

The same variety of corn was used in the four plots. Explain the importance of this.

6b2 marks

Consider the data in Table 1. What was the effect of watering corn with a mixture of freshwater and seawater?


6c3 marks

The students conclude that watering corn with diluted seawater might not be sustainable if this is repeated every year. Considering the data in Table 1, do these data support this conclusion?

6d2 marks

For the investigation carried out by the students, state a dependent variable and explain what is meant by the dependent variable.

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