Maintaining biodiversity

The Farne Islands are a group of small islands off the coast of Northern England.

The Farne Islands are a National Nature Reserve and Site of Special Scientific Interest. They are home to many species of bird, including arctic terns, guillemots, cormorants, shags, eider ducks, razorbills, and a variety of gulls. Particularly popular with the public are puffins. Considered by some to be a keystone species, puffins are small birds with large colourful beaks that fly very close to the surface of the sea. They come to the islands only to breed, nesting in underground burrows.

Local tour operators transport large numbers of visitors to the islands each year but no visitors are allowed on the islands during the winter to allow conservation work to be carried out. Such work includes repairing boardwalks and fences, tagging individual birds, and counting how many puffin burrows have been in use.

In 2023, an outbreak of bird flu caused a drop in the numbers of many species, including puffins, and visitors were banned from the islands. Local tour operators reported a drop in income.

Identify evidence from the information above that supports each of the following claims:

Puffins are important for aesthetic reasons........

Puffins are important for ecological reasons........

Puffins are important for economic reasons........

The Farne Islands can be seen as an environmental resource that is affected by human activities.

Identify one example of conservation that is necessary as a direct result of human activities.

There are no mammalian predators, such as rats and stoats, on the Farne Islands. Mammalian predators eat birds and their eggs.

Part of the conservation work involves ensuring that the islands remain free of these mammalian predators.

Suggest how human activity could be responsible for the arrival of these predators.

There are two types of conservation: in situ and ex situ.

State the type of conservation taking place on the Farne Islands and give a reason for your choice.

Puffins, like many species on the Farne Islands, eat small fish. Their main predators are large gulls. Puffins are on the IUCN Red List for threatened species.

The puffin population can be estimated from the number of burrows that are occupied.

After the bird flu outbreak in 2023 the number of occupied burrows declined.

It is important not to disturb the burrows and there is not enough money available to allow puffin burrows to be constantly monitored, either by humans or cameras.

Suggest one other type of evidence that could be used to infer that a burrow was being occupied by puffins.

Discuss the effect a decline in puffin population could have on other species in the area.

Explain why the existence of a predator can improve the long-term survival of a species such as the puffin.

* The sea around the Farne Islands contains a large population of grey seals, Halichoerus grypus and a small population of common seals, Phoca vitulina.

The table contains some information about these two species of seal.

Use the information in the table to describe the different types of variation between organisms and the underlying causes of this variation.

Extra answer space if required.

Grey wolves became extinct in an area of North America in the 1920s. In 1993 some grey wolves were reintroduced into the same area.

Grey wolves feed mainly on large herbivores, such as deer.

The graph shows the population of grey wolves and some other species since the reintroduction.

Describe the changes in the deer population since 1993.

Calculate the percentage increase in the wolf population between 1995 and 2003.

Between 2003 and 2010 there were no significant changes in the climate of this area of North America and no disease outbreaks.

Suggest and explain one reason for the changes in the grey wolf population since 2003.

Beavers are mammals that live in water. They form colonies nesting under big mounds of wood set as islands in areas of water.

In 1993 there was one colony of beavers living in the area to which the wolves were reintroduced.

Suggest why the population of beavers is measured in colonies rather than individual animals.

Scientists have claimed that the reintroduction of the wolves has caused the beaver population to increase.

Evaluate the support given by the evidence in the graph for the scientists’ claim.

Beavers build dams in the water using trees they have cut down. Deer damage trees while they are feeding. Wolves often hunt deer that are feeding near water.

The following explanation for the increase in beaver population has been suggested by scientists:

• The presence of wolves causes deer to avoid grazing close to water.

• This means that trees near water are not damaged.

• Beavers have a plentiful supply of trees with which to build dams.

Suggest one other piece of useful evidence that could be measured that would support the scientists’ claim.

Beavers are a species that was once native to Britain. The species became extinct in Britain about 400 years ago.

In 2009, a population of beavers was brought from Norway and released into the wild in Britain.

Explain why the reintroduction of beavers to Britain is an example of conservation.

Suggest a situation in which preservation of a habitat would be necessary.

The Convention on International Trade in Endangered Species (CITES) came into effect in 1975.

The kakapo, shown in Fig. 4.3, is an endangered species of flightless bird that lives in New Zealand. The population size of kakapos has experienced a large decrease over the past few hundred years. There are now fewer than 250 kakapos living in the wild.

State the term for a large decrease in population size that reduces the gene pool.

Adaptations can be categorised into three different types:

• anatomical

• behavioural

• physiological.

The table lists four traits that kakapos have evolved.

Complete the table by naming the type of adaptation represented by each of the four

The kakapo and two other species of bird, the kaka and the kea, evolved from a common ancestor approximately 70 million years ago.

The evolutionary timeline of the three species is shown in Fig. 4.4.

Fig. 4.4

Emergence of the Southern Alps mountain range

• The kakapo cannot fly. It forages for leaves and roots on the ground in forests and grasslands.

• The kaka can fly. It eats seeds, fruit, and occasionally the eggs of other birds in forest habitats.

• The kea can fly. It eats plants, larvae and other small animals. It lives in mountainous forest habitats.

• All three species live on the South Island of New Zealand and had overlapping ranges until the population size of kakapos started to decrease. Populations of kakas also live on the North Island of New Zealand.

A student studied the information and suggested that all three species evolved by sympatric speciation.

Evaluate the student’s conclusion.

New Zealand has a high species biodiversity compared to many countries.

Species biodiversity includes the concepts of species richness and species evenness.

Explain the difference between species richness and species evenness.

The Maasai Mara is a grassland ecosystem in east Africa with a large range of wildlife.

The human population in the area is increasing.

An increasing human population can affect the biodiversity of an area.

The wildlife present in the Maasai Mara includes several large mammals, such as gazelle, zebra and wildebeest.

Domestic animals, such as cattle, sheep and goats, are farmed by humans to provide food.

The graph below shows the population of some large mammals in the Maasai Mara between 1975 and 2007.

Wildebeest Gazelle Zebra Goat/Sheep Cattle

Calculate the rate of change in wildebeest population between 1975 and 2007.

Rate =........ animals per year

Maintaining biodiversity in the Maasai Mara is important.

The following are some statements about biodiversity in the Maasai Mara:

A People visit the Maasai Mara to see animals such as lions, giraffes and rhinoceros.

B Wild animals are sometimes killed for food by local people.

C Large herbivores such as wildebeest are the main source of food for large predators such as lions.

D Part of the area is used by farmers for grazing livestock.

E Soil erosion has occurred where trees have been removed by humans for fuel or to clear land for grazing.

F In and around the Maasai Mara there is accommodation for over 7000 tourists.

The reasons for maintaining biodiversity can be grouped into three categories: ecological, economic and aesthetic.

Fill in the table to show which of the statements, A to F, could be used as an example of the importance of each of the three categories.

You may use each letter once, more than once, or not at all.

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.

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.

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

Which of the following is most likely to increase biodiversity?

A captive breeding programmes

B climate change

C human population growth

D monoculture

Your answer

The Madidi National Park, in the South American rainforest, is home to a wide variety of species. The largest predator in the area is the jaguar. These large cats are well camouflaged and hunt mostly at night. A single individual can cover a very large area.

In 2007 the Wildlife Conservation Society (WCS) attempted to estimate the population of jaguars in the Madidi National Park.

• Digital camera traps were placed in areas that jaguars were likely to visit.

• If an infrared beam was broken by an animal, the camera was activated.

• The camera then took a photograph of the animal.

Suggest why it was not appropriate to estimate the number of jaguars using the capture-recapture technique.

Most studies estimate the population density of jaguars in the South American rainforest to be 5 individuals per 100 km².

In the 2007 study:

• 100 camera traps were set up covering an area of 271 km².

• 28 images of 9 different jaguars were recorded.

How well do these results support a population estimate of 5 individuals per 100 km²

Other evidence used to estimate the jaguar population includes footprints and reports of sightings by local humans.

Suggest one disadvantage of each of these methods for estimating the size of the jaguar population.

The Madidi National Park is also home to approximately 260 000 humans who support themselves by means of cattle-farming, and the production of timber and brazil nuts (a large nut harvested from a local native tree).

Conservationists have been working with:

• local people to promote sustainable use of these resources; and

• government agencies to maintain the quality of the national park.

Explain why the Madidi National Park is an example of conservation rather than preservation.