1. Food Chains and Food Webs

2. Food Chains and Food Webs
WALT: Draw a food chain and predict how external factors can alter the chain
I must correctly draw a food chain
I should be able to predict how external factors might causes changes to the chain
I could state how energy is lost at different stages

3. Let’s get started....
Watch this video of a baboon stalking a baby gazelle
(A baboon stalks a baby gazelle – bbc)
TASK: Can you draw a simple three component chain from the video showing the:
producer
primary consumer
secondary consumer
Draw on board
Points – baboon can be both primary consumer (when eating grass) and secondary consumer (when eating gazelle)
Producer is not always a plant – can be algae or can be decaying matter E.g. Decomposing animal
Draw on board an example e.g. Dead animal >> blow flies and maggots >> common frog >> grass snake
Definition of saprophyte
Original energy – from sun
DIRECTION OF ARROWS IMPORTANT (from producer to primary etc)...show direction of energy flow

4. Can you identify any errors in this food chain?
Errors – arrows in wrong direction
Not same habitat/area – clown fish (tropical), penguins (antarctica), polar bears (arctic)
Bad way of representing – should be straight line

5. Food chains and food webs
Food chains – represent flow of energy between different organisms that feed on each other
Each level called a “trophic (feeding) level”
Food chains can join together to become a food web – showing how the feeding of different animals in an area or habitat are linked
Question – why might a badger be a primary and a secondary consumer? (eats seeds but also earthworms).

6. Aquarium Ecosystem – look at the picture and answer the questions
1. Draw 3 food chains from this ecosystem
2. Combine your food chains to make a food web
3. Name 2 producers
Diatom = type of phytoplankton (autotrophic plankton)
4. Name 2 consumers

7. Answers
algae  snail  newt  catfish diatoms  fresh water mussel  newt  catfish diatoms  fresh water mussel  catfish algae  snail  catfish diatoms  water fleas  goldfish
(BEWARE OF ARROW DIRECTIONS)
2. Algae, diatoms, pond weed
3. Two from: snail, newt, catfish, mussel, water flea, goldfish

8. Watch the video clip and write down 6 or more key points
Energy from photosynthesis
- Food chains make up webs
- Plant eaters feed on grass – help more grass grow back in its place
- Each predator has own techniques for hunting prey
- Cheetahs run fast, lions slower – more sneaky
- Predators can work together but often compete
- Hyenas and cheetahs are competitors – attack each others cubs and steal food - - predators can become scavengers
- Large animals use up energy at slower rate therefore can go longer without food
- Food chain always starts as photosynthesis and ends in decay

9. Key points Identified in film
- Energy from photosynthesis
- Food chains make up webs
- Plant eaters feed on grass – help more grass grow back in its place
- Each predator has own techniques for hunting prey
- Cheetahs run fast, lions slower – more sneaky
- Predators can work together but often compete
- Hyenas and cheetahs are competitors – attack each others cubs and steal food - - predators can become scavengers
- Large animals use up energy at slower rate therefore can go longer without food
- Food chain always starts as photosynthesis and ends in decay

10. Make your own food web...3 mins
Construct a food web using the organisms below:
Slug
Hawk
Grass
Rabbit
Lettuce
Mistle Thrush

11. Copy questions into books – then discuss in pairs – 5 minutes.
What might happen if:
There was a disease of rabbits that killed off a large part of the rabbit population?
It was a year with exceptional sunshine and rain which meant that there was an extra large crop of lettuces and grass
Copy questions into books – then discuss in pairs – 5 minutes.
Hawk
Mistle Thrush
Rabbit
Slug
Lettuce
Grass

12. Your Task – in “KS3 Science – The Workbook (Living Things)”
Answer all the questions on p.71, p.74 and p.75 in full sentences NB: For p. 75 – your ‘ultimate predator’ and ‘ultimate prey’ – draw a sketch and label it

13. Plenary
Take your ‘ultimate predator’ and ‘ultimate prey’ and show and describe it to at least two other people in the class