1.4 Feeding People

1
1.4 Feeding People

• p. 25-34

2
Productivity

• The average amounts of new plant biomass produced
  each year per unit area.

3
Productivity of ecosystems

• Productivity is influenced by many factors

4
Factors that can increase productivity

• Add water and fertilizer to deserts
• Very expensive

5
Factors that can increase productivity.

• Clear cutting rain forest
• Introduce good farm plants and animals into
  rainforest conditions.
• Not a good idea.
• Disease, pests, weather fluctuations.

6
Food and Population Size

• Canadians consume more calories and more animal
  products per day than others in the world.
• 80 of the Earths population consumes grains as
  primary source of nutrition.

7
Food and Compeitiors

• Natural ecosystem hundreds of species are
  interconnected.
• Agricultural produces short, simple food
  chains, that link plants to people.

8
Factors that increase productivity.

• Monoculture
• A single crop (wheat, corn or rice) is often
  grown on huge areas of land.
• How does monocultural affect populations of
  primary consumers?

9
Costs of monoculture pests
10
Poisons and food chains

• To keep pests from damaging crops, many farmers
  spray their fields with poisionous chemicals,
  called pesticides.
• The pesticides are designed to kill insects but
  not harm other animals, in small doses.
• Problems occurs when pesticides enter food chains
  and pass from one trophic level to another.

11
The DDT Story

• DDT used during WWII to kill lice, fleas and
  mosquitoes.
• Persistant pesticide that can remain in the
  ecosystem for large periods of time.

12
The DDT Story

• Used on crops to control damage caused by insect
  pests

13
The DDT Story

• In 1962 Rachel Carson published Silent Spring
• DDT restricted in Canada after 1969

14
The DDT Story

• DDT is a great example of biological
  magnification.
• The concentration of chemical increases as you
  move up each trophic level in a food chain.

15
What you need to do now

• Read p. 30 31
• Do p. 32 1-11 omit 10
• Do p. 34 1-5