For IGCSE O-Level Biology students Chapter 17

1. Are we making things better or worse?

2. Agriculture: Using
pesticides:
 Advantages: kills pests
to increase crop yield.
 Disadvantages:
1. Non-biodegradable; may
persist in food chain and
kill top carnivores.
2. Causes emergence of
resistant pests.
3. Non-specific; kills
harmful as well as useful
organisms.

3. Biological control
 The use of the
natural predator of
the pest to
decrease their
numbers to
increase the crop
yield. This is safer
to the environment.

4. Deforestation
Reasons for cutting
down rain forests:
 1. provide land for
growing
crops, building new
cities, roads or
factories.
 2. use wood for
making
paper, furniture, build
houses.

6. Over-use of inorganic fertilisers.
 Eutrophication:

7. Air pollution: Acid rain

8. Acid rain causes:

9. Air pollution: nuclear fall out
The radioactive particles land
onto the ground, contaminate
water & enter food chains.
If they accumulate in tissues of
organisms they may cause
cancer or genetic damage.

10. Household waste

11. How can we help?

12. biogas

13. Biofuel