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)

Question 7

what does N stand for in an index of diversity

Answer 7

N = total number of organisms of all species

Question 8

what does n stand for in an index of diversity

Answer 8

n = total number of organisms of each species

Question 9

what does Σ stand for in an index of diversity

Answer 9

-the sum of

Question 10

list the steps involved in calculating an index of diversity

Answer 10

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 11

describe how index of diversity values can be interpreted

Answer 11

-high → many species present (high species richness) and species evenly represented
-low → habitat dominated by one / a few species

Question 12

name some farming techniques that reduce biodiversity

Answer 12

-removal of woodland and hedgerows
-monoculture (growing one type of crop)
-use of herbicides to kill weeds
-use of pesticides to kill pests

Question 13

describe how removal of woodland and hedgerows,
monoculture, use of herbicides to kill weeds reduce biodiversity

Answer 13

-reduces variety of plant species
-so fewer habitats and niches
-and less variety of food sources

Question 14

describe how the use of pesticides reduce biodiversity

Answer 14

-predator population of pest decreases

Question 15

explain the balance between conservation and farming

Answer 15

-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 16

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

Answer 16

-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