Food Chains and Food Webs

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

Let’s get started.... Watch this video of a baboon stalking a baby gazelle http://www.youtube.com/watch?v=eJi7p5GcLxg (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

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

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).

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

Answers 1. 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

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 http://www.youtube.com/watch?v=3Bn7wdCP2v4

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

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

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

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

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