Biodiversity (OCR A Level Biology): Exam Questions

Individuals within populations vary. Much of this variation is under genetic control.

Two groups of scientists were studying genetic polymorphism in fruit flies.

They extracted DNA from two different species of fruit fly, A and B.

The first group of scientists studied 26 gene loci from species A. They calculated the genetic polymorphism of species A to be 0.35.

The second group of scientists studied 32 gene loci from species B. They found that 13 of the gene loci were polymorphic.

(i) Calculate the proportion of genetic polymorphic gene loci of species B.

[2]

(ii) Evaluate the conclusion that species B shows greater genetic polymorphism than species A.

 [3]

Ecologists were studying an area that contained three different habitats. The area is shown in the diagram below.

The ecologists sampled the area to estimate insect biodiversity.

Describe how the ecologists should choose the number and locations of their samples to ensure that the sampling is representative.

Use a calculation to support your answer.

Two of the insect species that were sampled were the large heath butterfly and the bog hoverfly.

The ecologists used the capture‐mark‐recapture technique and estimated population sizes using two different calculations: the Lincoln estimate and the Chapman estimate.

(i) Calculate the population sizes of the two insect species using each of the formulae below.

Write your answers in the table.

Lincoln estimate formula:    population size =  Chapman estimate formula:      population size = 

n = number of individuals in a particular sample
m = number of marked individuals in the second sample

[2]

(ii) The Lincoln and Chapman formulae give different estimates for population size.

Give two further conclusions about the difference in population estimates given by the Lincoln and Chapman formulae.

[2]

The peat bog habitat had been damaged by peat extraction and by management of the neighbouring farmland. Ecologists decided to treat the peat bog in the following way:

• A buffer region was created between the peat bog and the neighbouring farmland.

• No visitors were allowed on the land.

• Ditches were blocked to raise water levels.

• Peat extraction, tree planting and the use of fertilisers were banned.

A student suggested that this was an example of preservation.

Evaluate the student’s conclusion.

Conservation agreements can be national (within a particular country) or international.

Three conservation agreements are listed in the table below.

Place ticks (✓) in the correct boxes to indicate which features are true for each of the three conservation agreements.

A group of ecologists wanted to assess the impact of different types of grazing on the diversity of ground-living beetles.

They collected samples of beetles from from fields with three different types of grazing:

1. Sheep grazing

2. Cow grazing

3. Horse grazing

The results of the sampling can be seen in Fig. 1 and Fig. 2 below:

Identify the field that shows the highest level of species richness. Explain your answer.

(i) Describe a sampling method that the ecologists could have used to collect their data for the study described in part (a).

[2]

(ii) State three considerations that the ecologists should have taken into account when planning and carrying out the investigation described in part (a).

[3]

A student reading the results of the ecology study shown in part (a) concluded that cow grazing was the best way to manage land for beetle diversity, and that sheep grazing was the worst for beetle diversity.

Evaluate the student's conclusion.

Table 1 contains additional information collected from field 1.

Table 1

Calculate Simpson's index of diversity (D) for field 1.

The formula for Simpson's index of diversity is provided below.

The same data was collected for field 3. This data is shown in Table 2 below.

Table 2

(i) Suggest how the index of diversity for field 3 would compare to that for field 1. 

Do not carry out any further calculations.

[1]

(ii) Suggest the cause of the difference in beetle diversity between the different fields in the investigation.

[2]

Biodiversity can be measured at different levels.

For each of the scenarios described below, identify the type of diversity being measured.

(i) Sweep net sampling in long grass reveals 23 species of invertebrate.

[1]

(ii) Researchers discover that variation exists between the call length of individuals in a bird population.

[1]

(iii) A marine ecosystem is found to contain seagrass meadows, silty mud, a coral reef and a mangrove forest.

[1]

(iv) More species are identified in a chalk grassland habitat than in an ancient woodland habitat.

[1]

Describe how agriculture can reduce biodiversity.

Agriculture is not the only human activity that affects biodiversity around the world, and many now agree that the conservation of biodiversity is essential.

Name two reasons for conserving biodiversity, and give an example for each.

Discuss the role of ex-situ conservation in maintaining biodiversity.

The Eurasian beaver, Castor fiber, was hunted to extinction in Finland during the 1800s, but was reintroduced into the country in the mid-1900s.

The graph below shows the changes in the Eurasian beaver population in Finland from the mid-1900s until 2020.

Calculate the percentage increase in the Finnish population of the Eurasion beaver between 1985 and 2020.

The beaver reintroductions carried out in Finland in the mid-1900s involved the release of a small number of individuals from Norway.

A group of scientists compared the genetic diversity of the beaver populations in Finland with populations in countries that did not experience complete beaver extinction.

Some of their data is shown in the table below.

(i) Calculate the proportion of polymorphic gene loci in the Finnish beaver population.

[2]

(ii) Explain the potential impact of this result on the future of the Finnish beaver population.

[2]

(iii) Suggest an explanation for the differences in genetic polymorphism levels between Finland and Germany/Russia.

[2]

Measuring genetic polymorphism levels is one way of assessing genetic diversity.

(i) Suggest why the proportion of genetic polymorphism is not a perfect measure of genetic diversity.

[2]

(ii) Name three factors, other than any that might have been covered in part (b), that can influence genetic diversity.

[3]

Beavers are known as a keystone species, meaning that their presence in an ecosystem is essential for the maintenance of the ecosystem.

Reintroduction of beavers in Finland has led to many ecosystem changes in the areas where they are present. Observed changes include:

• Beavers use their teeth to gnaw through tree trunks, resulting in tree felling

• Dead wood may be left behind in the forest after trees are felled

• Beavers use some logs from tree felling to build dams across waterways, slowing the flow of water

• Large bodies of standing water can result from the slowed water flow

Explain how biodiversity will be positively affected by the reintroduction of beavers to an ecosystem. Include at least one example in your answer.

Genetic biodiversity within populations can be assessed through DNA analysis.

Genetic polymorphism was investigated in captive male and female Asian elephants (Elephas maximus).

The results are shown in the table below:

(i) Calculate the proportion of genetic polymorphic gene loci of each group of elephants. 

[3] 

(ii) Evaluate the conclusion that female Asian elephants show greater genetic polymorphism than male Asian elephants. 

[3] 

African elephants (Loxodonta africana) have been found to have low genetic diversity. Suggest and explain the reasons for this.

There are some limitations to using the proportion of polymorphic genetic loci to assess genetic diversity.

Explain why genetic polymorphism alone does not give an accurate indication of genetic diversity.

(i) Explain why sampling is important when measuring the biodiversity of a habitat. 

[2]

(ii) Species richness and species evenness must both be measured in order to calculate Simpson’s Index of Diversity.

Explain the difference between these two measurements. [2]

Biodiversity can be measured using Simpson’s Index. An investigation was carried out to assess the biodiversity of plant species in two gardens.

The results of the investigation and calculated Simpson’s Index for one of the gardens are shown below.

(i) Calculate the Simpson’s Index of Diversity (D) for Garden B.  Use the formula: 

[3]

(ii) Analyse what the data show about the two gardens.

[1]

(iii) Explain why garden A is likely to represent a more stable ecosystem.

[2]

Suggest two possible sources of error in this investigation. 

The strangler fig is the common name for plants in the Ficus genus. They are found in some forest communities in tropical America and bear fruit several times a year, often when other plants do not.

(i) Explain the role that the strangler fig plays within the ecosystem in which it is found.

[3]

(ii) Strangler figs begin life as a sticky seed on a tree branch and often smother and outcompete their hosts, however, there is some evidence that trees encased in strangler figs are more likely to survive storms. Explain why this is an example of a mutualistic relationship. [2]

The silvery gibbon, Hylobates moloch, lives in the rainforests of the Indonesian island of Java. It was the first species to be protected by law in Indonesia in 1925 and is now on the IUCN Red List of Threatened Species.

Two recent estimates of the population of silvery gibbons in the Dieng Mountains are shown in the table below.

(i) Calculate the percentage increase in silvery gibbons in the Dieng Mountains between 2010 and 2021. 

[2]

(ii) The fixed point count in 2021 was completed by setting up listening posts at each sampling site to identify the calls of the gibbons.

The researchers identified two potential explanations for the data gathered. The first explanation was that the population size of gibbons had increased between 2010 and 2021.

Suggest another explanation for the apparent increase in population size.

[2]

The graph below shows the total number of species assessed by the IUCN over a 10 year period and the number of those species assessed that are considered to be threatened with extinction.

(i) Use the graph to calculate how many times greater the total number of species threatened was in 2008 compared to 2002. Give the answer to three significant figures.

[2]

(ii) Suggest explanations for the shape of the two curves between 2002 and 2004. 

[3]

The Bornean orangutan, Pongo pygmaeus, is a critically endangered member of the family Hominidae. Its population has declined by more than 50% over the past 60 years.

(i) Suggest two reasons why this population is critically endangered in the wild. 

[2]

(ii) Northwest Bornean orangutans are the most threatened subspecies; many of the habitat patches in the Northwest of Borneo. The image below shows how they are distributed.

Suggest why this may speed up the extinction of the orangutans.

[2]

The majority of wild orangutan populations are located outside of protected areas. Several initiatives have been put in place to conserve the habitats of Bornean orangutans including planning the use of land to ensure that agricultural areas are developed at an appropriate distance from their habitats.

Explain other methods of in situ conservation that could be used to further protect the Bornean orangutans in this area and the benefits of these over ex situ methods.

The values for Simpson’s index of diversity of three different habitats found on farmland were calculated and are shown in the graph below.

(i) Calculate the percentage difference between the Simpson’s index of diversity values in the centre of the field and in the hedge between the fields.

[2]

(ii) The standard deviations for the data are shown in the table below.

Explain what the standard deviations indicate about the data.

[2]

(iii) Explain how the data should be gathered to ensure that the values were representative of each of the different habitats.

[2]

The farmer who owns the land that was studied has the option of signing up to the Environmental Stewardship Scheme (ESS) which replaced the Countryside Stewardship Scheme (CSS) in 2005.

Explain the benefits to the farmer and the environment of joining this scheme.