3.4.6 - Biodiversity within a community

Question 1

What is biodiversity?

Answer 1

● Variety of living organisms (species, genetic and ecosystem diversity)
● Can relate to a range of habitats, from a small local habitat to the Earth

Question 2

What is a community?

Answer 2

All populations of different species that live in an area

Question 3

What is species richness?

Answer 3

A measure of the number of different species in a community

Question 4

What does an index of diversity do?

Answer 4

Describes the relationship between:
1. The number of species in a community (species richness)
2. The number of individuals in each species (population size)

Question 5

Suggest why index of diversity is more useful than species richness

Answer 5

● Also takes into account number of individuals in each species
● So takes into account that some species may be present in small or high numbers

Question 6

What is the formula for index of diversity?

Answer 6

d = N (N - 1) / Σ n (n -1)

• N = total number of organisms of all species
• n = total number of organisms of each species,
• Σ = the sum of

Question 7

List the steps involved in calculating an index of diversity

Answer 7

1. Calculate the total number of organisms (N), if not given
2. Multiply N by (N - 1)
3. For each species, multiply the number of organisms (n) by (n - 1)
4. Add up all the values of n(n - 1) to get Σn(n - 1)
5. Divide N(N - 1) by Σn ( n -1)

Question 8

Describe how index of diversity values can be interpreted

Answer 8

● High → many species present (high species richness) and species evenly represented
● Low → habitat dominated by one / a few species

Question 9

Explain how some farming techniques reduce biodiversity

Answer 9

> Removal of woodland and hedgerows
Monoculture (growing one type of crop)
Use of herbicides to kill weeds
● Reduces variety of plant species
● So fewer habitats and niches
● And less variety of food sources

> Use of pesticides to kill pests
● Predator population of pest decreases

Question 10

Explain the balance between conservation and farming

Answer 10

● Conservation required to increase biodiversity
● But when implemented on farms, yields can be reduced, reducing profit / income for farmers
○ Eg. by reducing land area for crop growth, increasing competition, increasing pest population
● To offset loss, financial incentives / grants are offered

Question 11

Give examples of how biodiversity can be increased in areas of agriculture

Answer 11

● Reintroduction of field margins and hedgerows (where farmers only grow one type of crop)
● Reduce use of pesticides
● Growing different crops in the same area (intercropping)
● Using crop rotation of nitrogen fixing crops instead of fertilisers

Question 12

Niche

Answer 12

• Role of an organism in its habitat (its interaction within the habitat and with other species in the community)
  > A species is adapted to its niche
  > niches are occupied by species

Question 13

Habitat

Answer 13

place in an ecosystem in which a community lives

Question 14

Ecosystem

Answer 14

Dynamic species in which abiotic and biotic factors interact