Biology

1. IGCSE
BIOLOGY
21
Human and the
environment

2. Population increase in the last 300 years has had
three main effects on the environment:
1. intensification of agriculture: destroying
wildlife and their habitats and effecting climate
as well as deteriorating the soul and polluting
the rivers due to chemical fertilizers
2. urbanization: less land available for wildlife,
problems of waste disposal (sewage), spread
of disease and pollution
3. industrialization: increase in manufacturing
industries leading to production of waste

3. Food Supply
21.1

4. Learning Objective
• State how modern technology has resulted in
increased food production in terms of:
– agricultural machinery to use larger areas of
land and improve efficiency
– chemical fertilisers to improve yields
– insecticides to improve quality and yield
– herbicides to reduce competition with weeds
– selective breeding to improve production by
crop plants and livestock, e.g. cattle, fish &
poultry

5. Section 5
Use of Biological Resources
• a) Food production
• b) Selective breeding
• c) Genetic modification (genetic engineering)
• d) Cloning

6. Food production
CROP PLANTS
Greenhouses and polythene tunnels raise the temperature, which increases
the rate of photosynthesis, which increases crop yield.
(Yield - The total mass of the edible part of crop.)
1) If the level of CO2 in the greenhouse is increased  the yield will further
increase .
2) Heating units increase temperature and CO2. (combustion)
(remember, CO2 is a limiting factor in photosynethsis)
3) In winter months using artificial lights gives a ‘longer day’ for growing
4) Transparent glass and plastic allow short wave energy in (light) and reflect
long wave energy back (heat) to keep temperature high.

7. Glasshouses and Polythene tunnels

8. Fertilizer and Crop Yield
If fertilizers are added (specifically those that contain
Potasium, Nitrate and Phosphate– KNP fertilisers) then the
yield will increase even more!
Potassium – essential for plant membranes
Nitrate – essential for making plant
proteins
Phosphate – essential for DNA and membranes

9. • Nitrogen is used to make
protiens
• Proteins increase biomass
(more plant)
• Increase in biomass increases
marketable part of the crop
( on a plant)
• Increased crop increases
revenue
(the cost of fertilizer must be less
then the increase in value of the
crop)
Fertilizer and Crop Yield
5.3 understand the use of fertiliser to increase crop yield