Boardworks Ltd 2003 Teachers Notes A slide contains

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Food web reminder human fox tuna 2. Name two herbivores in this foodweb. cow chicken Small fish 1. Name the producer in this foodweb. 3. Name a species that is both a primary consumer and a secondary consumer. 4. Name two species that are eaten by owls. shrimp plants 5. Where do plants get their food? © Boardworks Ltd 2003

Photosynthesis Chloroplast They contain a green pigment These are small structures called chlorophyll. that vary in number and size. LIGHT Chlorophyll The. Photosynthesis chlorophyll traps is the sunlight nameand of the Therefore, Chloroplasts are chemical uses thisreaction energy to that drive produces thewhere the a plant makes its own food. process ofplant’s photosynthesis. food. © Boardworks Ltd 2003

Photosynthesis We know that plants make their own food from sunlight. They are the producers in the food chain. This is done in the green parts of the plant, e. g. upper surface of the leaves. The reaction for this is: CARBON DIOXIDE + Taken in through holes in the leaves WATER Taken in through the roots FOOD (GLUCOSE) + Made from photosynthesis and stored as starch in leaves, roots, stems, etc. OXYGEN waste product exhaled + ENERGY USEFUL! © Boardworks Ltd 2003

Respiration Plants also respire, just like animals, because they also need energy. FOOD (GLUCOSE) Made from photosynthesis and stored as starch in leaves, roots, stems, etc. + OXYGEN CARBON DIOXIDE Taken in through holes in the leaves waste product exhaled + WATER waste product exhaled + ENERGY USEFUL! © Boardworks Ltd 2003

Food from plants Plants provide us with food in many different forms. Some foods may be part of the root, others may be in the leaf, the stem or in seeds. • Identify where some of the foods below came from. • Why do plants store food in these parts? © Boardworks Ltd 2003

Food chains and poisons Unfortunately the introduction of poisons at the bottom end of a food chain can have huge effects on the organisms at the top of the food chain. Look at the following lake food chain: plankton zooplankton small fish large fish grebe (bird) A chemical – DDT mosquito larvae. was sprayed on the lake to control What do you think happened next? © Boardworks Ltd 2003

The plant plankton absorbed some of the DDT from the water. Zooplankton ate many plant plankton and got more than one dose of DDT. Each zooplankton had 5 ppm of DDT in it. Each small fish ate many zooplankton. Therefore it got more than one dose of DDT. How much DDT do you think each small fish had in it? Each small fish had 10 ppm of DDT in it. Each large fish ate several small fish therefore getting more than one dose of DDT. How much DDT do you think each large fish had in it? Each large fish had 250 ppm of DDT in it. Each grebe ate several large fish therefore getting more than one dose of DDT. How much DDT do you think each grebe had in it? © Boardworks Ltd 2003

Each grebe had an amazing amount of 1600 ppm of DDT in its tissue. If this didn’t kill the bird (which it often did) it caused the eggs that were laid to have very thin shells. The eggs broke very easily and not many chicks were born alive. This is a true story that happened in the USA in the 1950’s. DDT led to the decline of many species of birds. So as you can see a little bit of poison at one end of a food chain can add up to a lot at the other end. Fortunately, pesticides like DDT have now been banned in most industrial countries. © Boardworks Ltd 2003

You are a biologist who has been hired by a company that specialises in growing and selling roses. They have had a big problem with aphids eating their roses. In order to control the aphids they have decided to apply a pesticide to all of their rose bushes. Before they do this they want you to write a report on the effects this pesticide will have on other organisms in the rose bush food web. Use the food web on the next page to help you. Make sure you include what will happen to all other members of the food web. Discuss both what will happen to their numbers and how they will be affected by the pesticide in the food chain. At the end of the report give your professional opinion on whether you think the company should apply the pesticide. Maybe you could give them some alternatives to pesticides. © Boardworks Ltd 2003