• Species diversity is the total number of species in a community.
• Humans have has a negative impact on species diversity with intensive farming and deforestation.

• The following forms of intensive farming and decreased species numbers:
  • monoculture
  • hedgerows
  • fertilisers
  • pesticides
• Monoculture involves only one crop being grown which reduces genetic diversity.
• The removal of hedgerows has destroyed the habitat and food source of many species.
• Inorganic fertilisers leach out causing eutrophication.
• Artificial pesticides contain dangerous chemicals that stay in the soil and can build up in food chains.
• Deforestation is where huge areas of forest are destroyed, mainly for agricultural reasons.
• Deforestation has led to species of tree becoming extinct and had a dramatic effect on food webs.
• The index of diversity:

d = N (N – 1)

? n (n – 1)

Complete the test below to help your a level biology revision:

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TEST IT!

1.

A farmer grows corn. He decides to look into intensive farming
a) Name two ways intensive farming methods he could use and a benefit to him for using it?
i. Method ______________________________________
ii. Benefit_______________________________________
iii. Method ______________________________________
iv. Benefit _______________________________________
b) Provide two ways in which intensive farming has a negative impact on biodiversity.
i. _____________________________________________
ii. _____________________________________________

2.

Large parts of the Amazon rainforest are being cut down to make room to grow crops such a soya beans. This is having a large negative impact on different species which live in the rainforest and the whole region is being polluted by chemicals and metals. Provide a way in which deforestation has a negative effect on the following species:
a) hard wood trees
b) jaguars
c) Amazon River dolphins
d) humans

A group of biologists decide to look at four species in two different ecosystems to compare the diversity in each region. The results they collected are in the table below.

Calculate the diversity index for each ecosystem. Which ecosystem has the most diversity?

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ANSWERS

1.

a) Answers include:

i. Monoculture: save money, less work, concentrate on one crop only
ii. Fertilisers: grow crops faster, less work
iii. Pesticides: grow crops faster, less work

b) Answers include

i. Reduces genetic diversity
ii. Cause eutrophication
iii. Reduce the land available for species to live on and find food and shelter
iv. Poisonous chemicals are dangerous to wildlife
v. Chemicals build up in the food chain (bioaccumulation)

2.

Answers include:
a) Leads to extinction
b) Gets rid of their habitat, affects prey numbers
c) Chemicals leach into the water
d) Useful species become extinct

Use the equation: d = N (N – 1)
? n (n – 1)

Ecosystem 1: 102 x (102 – 1)
[24 x (24 – 1)] + [28 x (28 – 1)] + [32 x (32 – 1)] + [18 x (18 – 1)]

= 10302 = 3.95 (2dp)
2606

Ecosystem 2: 99 x (99 – 1)
[15 x (15 – 1)] + [24 x (24 – 1)] + [17 x (17 – 1)] + [43 x (43 – 1)]

9702 = 3.42 (2dp)
2840

Conclusion: Ecosystem 1 has more diversity