Section 11: Biodiversity

Question 1

What does biodiversity mean?

Answer 1

The term ‘biodiversity’ refers to the variety of living organisms in an area. It can be considered at three different levels:
Habitat diversity
Species diversity
Genetic diversity

Question 2

What is habitat diversity?

Answer 2

A habitat is an area inhabited by a species. It includes the physical factors, like the soil and temperature range, and the living (biotic) factors, like availability of food or the presence of predators. Habitat diversity is the number of different habitats in an area.

Question 3

Give two examples of habitat diversity.

Answer 3

A coastal area could contain many different habitats - beaches, sand dunes, mudflats, salt marshes, etc.
A river valley could contain meadows, agricultural fields, streams, woodland, etc.

Question 4

What is species diversity?

Answer 4

A species is a group of similar organisms able to reproduce to give fertile offspring. Species diversity is the number of different species (species richness) and the abundance of each species (species evenness) in an area.

Question 5

Give an example of species diversity

Answer 5

A woodland could contain many different species of plants, insects, birds and mammals.

Question 6

What is generic diversity?

Answer 6

Genetic diversity is the variation of alleles (versions of a gene) within a species or a population of a species.

Question 7

Give examples of genetic diversity?

Answer 7

Human blood type is determined by a gene with three different alleles.
The variation in alleles within the dog species gives rise to different breeds, such as labrador or poodle.

Question 8

What does it mean to collect data on biodiversity?

Answer 8

Collecting data on biodiversity usually means finding out the number of different species in a habitat or the number of individuals in each species. In most cases though, it’d be too time consuming to count every individual organism in a habitat. Instead, a sample of the population is taken. Estimates about the whole habitat are based on the sample.

Question 9

Describe random sampling.

Answer 9

To make sure that a sample isn’t biased, it should be random. For example, if you were looking at plant species in a field you could pick random sample sites by dividing the field into a grid using measuring tapes and use a random number generator to select coordinates. Doing this makes sure that each sample site has the same probability of being chosen.
To ensure any variation observed in the sample isn’t just due to chance, it’s important to analyse the results statistically. This allows you to be more confident that the results are true and therefore will reflect what’s going on in the whole population.

Question 10

When is a non-random sample necessary?

Answer 10

Sometimes it’s necessary to take a non-random sample. For example, when there’s a lot of variety in the distribution of species in the habitat and you want to make sure that all the different areas are sampled or that all the different species are sampled. There are three types of non-random sampling
Systematic sampling
Opportunistic sampling
Stratified sampling

Question 11

Describe systematic sampling and give and example

Answer 11

This is when samples are taken at fixed intervals, often along a line.
If you were looking at plant species in a field, quadrats (square frames that you place on the ground) could be placed along a line (called a transect) from an area of shade in the corner to the middle of the field. Each quadrat would then be a sample site.

Question 12

What is opportunistic sampling?

Answer 12

This is when samples are chosen by the investigator, it’s used because it is simple to carry out, but the data will be biased.

Question 13

What is stratified sampling and give an example

Answer 13

This is when different areas in a habitat are identified and sampled separately in proportion to their part of the habitat as a whole.
For example, a heathland may have patches of gorse on it - the heath and gorse areas would br sampled separately according to how much of each there was in the habitat.

Question 14

What are the factors affecting biodiversity?

Answer 14

Habitat loss, over-exploitation, urbanisation and pollution.

Question 15

Describe habitat loss is caused due to human population growth and give an example.

Answer 15

As the human population grows, we need to develop more land for housing and to produce food. This development is destroying habitats.
For example, there is deforestation in the Amazon to make way for grazing and agriculture. This decreases habitat diversity. With fewer habitats for organisms to live in, species diversity also decreases.

Question 16

Describe over-exploitation Is caused due to human population growth and give an example.

Answer 16

A greater demand for resources (such as food, water and energy) means a lot of resources are being used up faster than they can be replenished. This can destroy habitats or it can affect species directly.
For example, industrial fishing can deplete the populations of certain fish species and may even cause extinction (a species to die out). This decreases genetic diversity within populations, as well as decreasing species diversity (as a result of extinction).

Question 17

Describe urbanisation is caused due to human population growth and give an example.

Answer 17

Sprawling cities and major road developments can isolate species, meaning populations are unable to interbreed and genetic diversity is decreased.
For example populations of some animals, for example snakes, living in areas isolated by roads show a lower genetic diversity than populations living in areas of continuous habitat. This is thought to be because the isolated animals are unable to migrate and breed as they usually would.

Question 18

Describe how pollution is caused due to human population growth and give examples.

Answer 18

As the human population grows, we’re producing more waste and more pollution. High levels of pollutants can kill species or destroy habitats.
For example, high levels of fertiliser flowing into a river from nearby fields can lead to a decrease in fish species in that river. This decreases biodiversity.
Some of the gases that are released from factories and cars cause acid rain, which can lower the pH of rivers, lakes and soil. Many aquatic organisms can’t survive below a certain pH.

Question 19

What is monoculture and give an example.

Answer 19

In order to feed an ever growing number of people, large areas of land are devoted to monoculture - the growing of a single variety of a single crop.
For example, in Africa, large areas of land are used for palm oil plantations.
This leads to a decline in biodiversity because of the following factors; habitat loss, loss of local plants and animals and loss of heritage varieties.

Question 20

Describe how habitat loss is caused due to monoculture and give an example.

Answer 20

Habitats are lost as land is cleared to make way for the large fields, reducing habitat diversity. This is not just the case on land. Marine fish farms are often built in locations that are ideal for wild fish and other marine life.
For example, mangrove forests are areas of trees that grow in tropical and sub-tropical coastal regions. They are rich in biodiversity and provide a habitat for a wide variety of plant and animal species. One of the biggest threats to mangrove forests comes from clearance to make space for shrimp farms.

Question 21

Describe how loss of local plants and animals is caused due to monoculture and give an example.

Answer 21

Local and naturally occurring plants and animals are seen as weeds and pests, and so are destroyed with pesticides and herbicides, reducing species diversity.
For example, the use of herbicides on corn farms in the USA kills the local milkweed plant, which is the main source of food for the stomach butterfly. Monarch butterfly numbers are decreasing, which may partly be as a result of this.

Question 22

Describe how loss of heritage varieties is caused due to monoculture.

Answer 22

Heritage (traditional) varieties of crops are lost because they don’t make enough money and so are not planted anymore, which reduces species diversity.

Question 23

Describe climate change and global diversity?

Answer 23

Climate change is a significant long-term change in an area’s climate, e.g. its average temperature or rainfall patterns. It occurs naturally, but the scientific consensus is that the climate change we’re experiencing at the moment is caused by humans increasing emissions of greenhouse gases (such as carbon dioxide). Greenhouse gases cause global warming (increasing global average temperature), which causes other types of climate change, e.g. changing rainfall patterns. Climate change can affect diversity by changing environmental conditions

Question 24

How can climate change affect biodiversity?

Answer 24

Climate change will affect the environmental conditions in different areas of the world in different ways - some places will get warmer, some colder, some wetter and others drier. All of these changes are likely to affect global biodiversity.
One reason for this is that most species need a particular climate to survive, so a change in climate may mean that an area that was previously inhabitable becomes uninhabitable (and vice versa). This may cause an increase or decrease in the range of some species (the area in which they live). This could increase or decrease biodiversity.
For example, the southern range limit of the Scooty Copper Butterfly has moved 60 miles north in recent decades.
Changing environmental conditions may force some species to migrate to a more suitable area, causing a change in species distribution. Migrations usually decrease biodiversity in the areas the species migrate from, and increase biodiversity in the same areas they migrate to. If there isn’t a suitable habitat to migrate to, the species is a plant and can’t migrate, or if they change is too fast, the species may become extinct. This will decrease biodiversity.
For example, corals die if water temperature changes by just one or two degrees. In 1998 a coral near Panama was badly damaged because the water temperature had increased - at least one species of coral became extinct as a result.