The material in this slide show is provided free for educational use only. All other forms of storage or reproduction are subject to copyright- please contact the National Marine Aquarium The slide show was designed and produced for the NMA by STEP, the Science Training & Education Partnership T raining & S cience E ducation P artnership

Food chains and food webs - ‘who eats whom’

Food chains and food webs What goes in, what comes out? Summary Sizes and numbers

Food chains and food webs What goes in, what comes out? Summary Sizes and numbers

Food chains show how food passes from one living thing to another

All food chains start with a Plant Plants can make their own food, using sunlight

GRASS A plant - makes its own food RABBIT An animal that eats plants FOX An animal that eats other animals The arrows show the food chain

GRASS A plant - makes its own food RABBIT An animal that eats plants FOX An animal that eats other animals The plant is a ‘producer’ PRODUCER

GRASS A plant - makes its own food RABBIT An animal that eats plants FOX An animal that eats other animals The rabbit is a ‘consumer’ - a herbivore or plant- eater PRODUCERCONSUMER

GRASS A plant - makes its own food RABBIT An animal that eats plants FOX An animal that eats other animals The fox is also a ‘consumer’ - a predator or meat- eater PRODUCERCONSUMER

Food chains work in the same way in the sea... … but the plants and animals look a bit different!

Out in the ocean, there is no grass or trees The plants are tiny ALGAE - you need a microscope to see them ALGAE Microscopic plants - make their own food COPEPOD A tiny animal that eats plants FISH An animal that eats other animals This is a food chain in the ocean

Out in the ocean, there is no grass or trees PRODUCERCONSUMER ALGAE COPEPOD FISH

The food chain won’t stop there...

In most habitats, there are several food chains These are linked together to form a Food Web

Food webs can be quite complicated Here is one from the ocean around Antarctica …

A simple food chain - whale eats krill eats algae Copepods also eat algae, and are eaten by krill Fish eat krill and copepods Squid eat fish and krill Seals eat squid and fish This food web contains 7 types of living things, and 9 food chains

Food chains and food webs What goes in, what comes out? Summary Sizes and numbers

Not all food eaten by an animal is turned into new body tissue - ‘growth’

In fact, for most animals, very little food contributes to growth Some cannot be digested, and is lost Much food is used to provide energy

An example: krill feeding on algae 70 grammes of algae eaten per day 10 grammes - about 15% - is indigestible 50 grammes of food are used to provide energy for swimming and catching more food This leaves 10 grammes of food that can be used for growth

70 grammes ‘in’ = 100% 50 grammes plus 10 grammes ‘to waste’ = 85% of food eaten 10 grammes to growth = 15% of food eaten

The same thing happens at every step along the food chain Look at the food web from Antarctica...

A large blue whale will eat 3 tonnes of krill each day The amount of growth will be 120 kilogrammes -96% of the food has ‘gone to waste’

Food chains and food webs What goes in, what comes out? Summary Sizes and numbers

The rate at which animals grow is often related to their body size

GRASS RABBIT FOX On land, herbivores and predators are often similar in size

In the oceans, both the plants and the herbivores are small. There are great size differences between herbivores and predators We can understand the size differences more easily if we match each living thing to familiar objects. Here, we magnify each 1000 times Making each alga cell 1000 times bigger means that it is about the size of a squash ball Making the krill 1000 times bigger means that it becomes as long as a small bus Making the whale 1000 times bigger means that it is still huge - it would stretch across the Isle of Wight

We have seen that most food eaten by consumers is either not digested or converted to energy Only a small amount is converted to growth This happens at each link in the food chain

The shortest food chain in the Antarctic food web has two links

LOSS

For 100 tonnes of algal growth... … there are 15 tonnes of new krill growth... … and there are only 600 kilogrammes of new whale growth

The longest food chain in the Antarctic food web has five links

LOSS

Now, for 100 tonnes of algal growth... … and there is only 1 kilogramme of new seal growth % of the algae eaten by the copepods has been lost

In the food chain with more links, more producer growth is lost

Food chains and food webs What goes in, what comes out? Summary Sizes and numbers

A food chain links plants and animals in a habitat All food chains start with a plant = producer You have seen that -

Food webs on land and in the ocean are similar In the ocean, plants and herbivores are small You have seen that -

Most food in a food chain is turned into energy and lost Long food chains waste more food than short ones You have seen that -

NOTES for USERS The material in this slide show is designed to support the teaching of science at Key Stage 1 A full description of the slide show, and linked activities for students, can be found on the National Marine Aquarium (NMA) web-site: Teachers are free to amend the slide show in whatever way they feel fit, or to use slides in other contexts. However, please note that neither the NMA nor the designers will accept responsibility for modifications, and original material remains copyright of the NMA Individual images used in the slides are copyright of NMA or STEP, except where acknowledged separately The slides have been set up to display as A4 landscape format. If they are incorporated into other slide sequences with different display settings, change in aspect ratio and text location will occur The slide sequence contains the minimum of effects and transitions. However, there are some automated animations, and teachers will wish to make sure that they are familiar with the sequence before use in class Use the PowerPoint notes viewer to obtain additional information for some slides