1. Topic 5: Ecology and evolution
5.1 Communities and ecosystems

3. Autotrophs vs hetertrophs
What do these words mean?
Give examples of organisms from each group.

5. detritivores Ingests and then digest dead organic matter
Eg. Earthworms, woodlouse

6. saprotroph An organism that lives in or on non-living organic matter
They secrete digestive enzymes into it and absorb the products of digestion
Digest first, then absorb
Nature’s recylers – recycle nutrients
Heterotrophs
Eg. Fungi, bacteria

7. consumer
An organism that ingests other organic matter that is living or recently killed
Heterotrophs

8. Food chains
Show the flow of energy through the trophic levels of a feeding relationship
Trophic level: feeding position of an organism in food chain
Each organism feeds on the organism before it
Arrows point towards the consumer
Indicate the direction of energy and nutrient flow

9. What is wrong with this?

10. challenge
Group A: Create a food chain with three linkages (four organisms) from a desert ecosystem
Group B: Create a food chain with three linkages (four organisms) from a grassland ecosystem
Draw on the whiteboard. Now lets label it together as a class.

11. Food chain examples Tertiary consumers Secondary consumers
Primary consumers
Producers

12. challenge
With your partner, read the following article and create a food web

13. challenge
Can you pick out a 3 step food chain and a 4 step food chain?
Can you find two organisms that fit into more than one trophic level?

14. Food web
Shows complex feeding relationships showing interacting food chains

15. Challenge answers

16. Energy
Light is the initial source of energy for almost all communities
This comes from the SUN

17. Energy flow relay game
Let’s go outside!

18. Energy flow
Energy flows through food chains, but some (90%) is lost between each trophic level
Loss is due to:
Material not consumed
Material not assimilated
Heat loss through cellular respiration
Nutrients are recycled

19. Energy pyramids Show the flow of energy between trophic levels
Never 100% efficient, around 90% loss
The width of the bars is proportional to the energy in that tropic level
Only approx. 10% of energy is passed on to the next trophic level.
Unit = kJ m-2 y-1

23. homework
DBQ pg. 169
Working with data pg. 170