Genetic Information and Variation - Biodiversity within a Community

Question 1

What is biodiversity?

Answer 1

Biodiversity is the general term used to describe variety in the living world. It refers to the number and variety of living organisms in a particular area.

Question 2

What are the three components of biodiversity?

Answer 2

• species diversity: number of different species and the number of individuals of each species within any one community
• genetic diversity: variety of alleles in a gene pool possessed by the individuals that make up a population of a species
• ecosystem diversity: number of different habitats

Question 3

How do you calculate species diversity? What is index of diversity?

Answer 3

N(N-1) / ∑n(n-1)

can be measured by simply counting the number of species preset via methods such as random sampling

Question 4

What is species richness?

Answer 4

One measure of species diversity is species richness. This is the number of different species in a particular area at a given time (community). It takes no account of the number of individuals or abundance.

Two communities may have the same number of species but the proportions of the community made up of each species may differ markedly.

Question 5

What is the benefit of having a high species diversity?

Answer 5

Biodiversity reflects how well an ecosystem is likely to function. The higher the species diversity index, the more stable an ecosystem usually is and the less it is affected by change. This is because there are at least some members that are likely to survive the change and maintain a community.

Question 6

Why has there been a reduction in biodiversity?

Answer 6

to provide enough food for the human population at a low cost, mankind has had a considerable impact on the natural world

• effects of farming
• effects of deforestation
• consumer demand
• technology demand

Question 7

What are natural ecosystems?

Answer 7

As natural ecosystems develop over time, they become complex communities with many individuals of a large number of different species. They have a high index of diversity.

Question 8

What are agricultural ecosystems?

Answer 8

Agricultural ecosystems are controlled by humans. Farmers often select species for particular qualities that make them more productive. As a result, the number of species and the genetic variety of alleles they possess is reduced to the few that exhibit the desired features.

Question 9

Why does the number of individuals of desirable species need to be large? What is the effect of this on biodiversity?

Answer 9

To be economic, the number of individuals of these desirable species needs to be large.

Any particular area can only support a certain amount of biomass. If most of the area it taken up by the one species that the farmer considers desirable, there is a smaller area available for the other species.

These many other species have to compete for what little space and resources are available. Many will not survive this competition. Even if species evolved to adapt to the changes, the population of the species would be considerably reduced.

Question 10

What is the effect of using pesticides and herbicides?

Answer 10

Pesticides are used to exclude other species because they compete for the light, mineral ions, water and food required by the farmed species. The overall effect is a reduction in species diversity. The index of species diversity is therefore low in agricultural ecosystems.

Question 11

How has food production increased?

Answer 11

By the use of improved genetic varieties of plant and animal species, greater use of chemical fertilisers and pesticides, greater use of biotechnology and changes in farm practices, leading to larger farms and the conversion of land supporting natural communities into farmland.

Question 12

What is the overriding ecological impact of intensive food production?

Answer 12

it has diminished the variety of habitats within ecosystems and consequently reduced species diversity

Question 13

What practices have directly removed habitats and reduced species diversity?

Answer 13

• removal of hedgerows and grubbing out woodland
• creating monocultures (e.g. replacing natural meadows with cereal crops or grass for silage)
• filling in ponds and draining marsh and other wetland
• over-grazing of land (e.g. upland areas by sheep, thereby preventing regeneration of woodland)

Question 14

What practices have indirectly removed habitats and reduced species diversity?

Answer 14

• use of pesticides, herbicides and inorganic fertilisers
• escape of effluent from silage stores and slurry tanks into water courses
• absence of crop rotation and lack of intercropping or undersowing

Question 15

What conservation techniques can be applied to increase species and habitat diversity, without unduly raising food costs or lowering yields?

Answer 15

• maintain existing hedgerows at the most beneficial height and shape
• plant hedges rather than erect fences as field boundaries
• maintain existing ponds and where possible create new ones
• leave wet corners of fields rather than draining them
• plant native trees on land with a low species diversity rather than in species-rich areas
• reduce the use of pesticides (use biological control where possible or genetically modified organisms that are resistant to pests)
• use organic fertilisers
• use crop rotation that includes a nitrogen-fixing crop to improve soil fertility
• use intercropping rather than herbicides to control weeds and other pests
• create natural meadows and use hay rather than grasses for silage

Question 16

Why are there financial incentives?

Answer 16

It is recognised that these practices will make food slightly more expensive to produce, and so to encourage farmers there are a number of financial incentives from the Department for Environment, Food and Rural Affairs and the European Union.

Question 17

What happens if biodiversity is reduced?

Answer 17

The global living system becomes increasingly unstable and we all rely on the global system for food and other resources.

Question 18

Why have hedgerows been removed in recent years?

Answer 18

Hedgerows were originally created to mark the boundaries of fields and to contain livestock. Since then, there has been a farming revolution with an increase in the use of large farm machinery and larger farm sizes. Small fields are not suited to the new machinery and so hedgerows are removed to make it easier to manoeuvre large equipment. Hedgerows also take up land that could produce crops and so farmers removed them, often with grants that were once available to increase productive land area.

Question 19

What are the uses of hedgerows?

Answer 19

They increase species diversity and act as corridors along which many species move to disperse themselves. They also produce food for both animals that live in hedgerows as well as those that do not.

Question 20

What is monoculture?

Answer 20

repeatedly growing the same crop on the same piece of land

Question 21

What are the key features of modern farming?

Answer 21

• large fields growing one type of crop
• more land being used as farm land
• high yield (more profit)
• hedgerow cut down to make larger fields
• larger farm machinery makes farming more efficient
• use of inorganic fertilisers, pesticides and herbicides
• intensive rearing of animals, more animals per unit area

Question 22

Monoculture has resulted in the removal of hedgerows to make larger fields. What are the advantages?

Answer 22

• more space for crops, no shading by tall hedges
• more room for larger machinery
• no cost in maintaining hedges
• removes habitat for crop pests

Question 23

What are the reasons for deforestation?

Answer 23

• clearing land for farming crops and cattle

- clearing land for housing, building, reservoirs

Question 24

What is conservation?

Answer 24

Conservation is the active maintenance of ecosystems and their biodiversity. But we need to balance conservation with the need to grow food for our growing human population.

Question 25

Why do we conserve?

Answer 25

1. ethical reasons: we have a responsibility not to destroy other species
2. economic reasons: we will need these ecosystems in the future (undiscovered medicine?)
3. aesthetic reasons

Question 26

What does an index of diversity describe?

Answer 26

the relationship between the number of species in a community and the number of individuals in each species