1. Science 9
Unit 4: Ecology
Lesson 3: Food Chains/Web & Bioaccumulation/Biomagnification

2. Objectives By the end of the lesson you should be able to:
Describe what a food chain and food web are
Describe how bioaccumulation effects an organism
Relate food chains/webs to biomagnification

3. Food Chains All food chains start with the sun
Arrow always points to who is doing the eating (E.G. where the energy is going)
(Note that the sun isn’t eating the flower!)

4. Terminology Producer: makes their own food
Primary consumer: eats the producer (aka: the herbivore)
Secondary consumer: eats the primary consumer (aka: a carnivore)
Tertiary consumer: eats the secondary consumer (aka: a carnivore)
Quaternary consumer: eats the tertiary consumer

5. Note: only 10% of an organisms energy gets passed up the pyramid

6. Detritivore VS Decomposer
Detritivores:
- Organisms that gain their energy from eating dead organisms or animals wastes
Decomposers:
- Organisms that break down organic matter into useable nutrients

8. Food Webs A number or inter-related food chains create a food web
Who’s who in this food web?

9. Your Turn!
Watch this video and see if you can label the organisms as they appear and create a food web!

10. Your Turn! Food chains/web activity: BC animals
Food chains/web activity: aliens!

11. BC Food Web

12. Trophic Level and % energy:
Alien Food Web
Autotroph or
Heterotroph?
Trophic Level and % energy:

13. Bioaccumulation
Gradual build up of synthetic and organic chemicals in living organisms
These chemicals build up because decomposers cannot break them down so they remain in an ecosystem
These chemicals usually build up in fatty tissues
These chemicals can effect the nervous, reproductive and immune systems

14. Chemicals PCBs: polychlorinated biphenyls
Used from Ex: coolants, lubricants
Banned in North America
POPs: persistent organic pollutants
Ex: DDT – introduced in 1941, now banned in most countries
Toxic at 5 ppm (part per million)
Heavy Metals: Pb, Cd, Hg
Lead: electronics; toxic at ppm
Cadmium: smoking, half life of 30 yrs!
Mercury: 40+% from coal burning

16. Biomagnification
Process where chemicals become more concentrated at each trophic level
More toxic for the higher trophic level organisms first – why?

19. Your Turn! Paperclip activity Product Research – if time! Percent %
Organism