Your SlideShare is downloading. ×
  • Like
Year 9 Biology Topic Plants for Food
Upcoming SlideShare
Loading in...5
×

Thanks for flagging this SlideShare!

Oops! An error has occurred.

×

Now you can save presentations on your phone or tablet

Available for both IPhone and Android

Text the download link to your phone

Standard text messaging rates apply

Year 9 Biology Topic Plants for Food

  • 2,467 views
Published

 

Published in Technology , Business
  • Full Name Full Name Comment goes here.
    Are you sure you want to
    Your message goes here
    Be the first to comment
    Be the first to like this
No Downloads

Views

Total Views
2,467
On SlideShare
0
From Embeds
0
Number of Embeds
0

Actions

Shares
Downloads
89
Comments
0
Likes
0

Embeds 0

No embeds

Report content

Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

Cancel
    No notes for slide

Transcript

  • 1. KS3 Biology 9D Plants for Food1 of 201 of 24 © Boardworks Ltd 2004 2005
  • 2. Contents 9D Plants for Food Plants as food Fertilizers and competition Pests and pesticides Summary activities1 of 202 of 24 © Boardworks Ltd 2004 2005
  • 3. Humans in food chains Humans eat many different foods and so are at the top of many food chains. What are the food chains for the ingredients in this slice of pizza? wheat (bread) human cow’s milk grass human (cheese) tomato human pepper human What do these and all food chains have in common?1 of 203 of 24 © Boardworks Ltd 2004 2005
  • 4. Plants as producers All food chains start with a producer. Plants are called producers because they produce the food that humans and all other consumers depend on. How do plants make their food? Plants use light energy to carry out photosynthesis: light energy carbon dioxide water glucose oxygen chlorophyll The glucose produced by plants is converted into starch for storage or used to make proteins, fats and other substances. Which parts of plants can be eaten?1 of 204 of 24 © Boardworks Ltd 2004 2005
  • 5. Food from plants Plants provide food in many different forms – some foods are from the leaf, the stem or the root of a plant, others are the seed or the fruit of a plant. Which parts of plants are these foods from?1 of 205 of 24 © Boardworks Ltd 2004 2005
  • 6. Which part of a plant?1 of 206 of 24 © Boardworks Ltd 2004 2005
  • 7. Contents 9D Plants for Food Plants as food Fertilizers and competition Pests and pesticides Summary activities1 of 207 of 24 © Boardworks Ltd 2004 2005
  • 8. Healthy plant growth Plants need carbon dioxide and water for photosynthesis but they also need small amounts of mineral salts for healthy growth. Where do plants get mineral salts from? Mineral salts are dissolved in water in the soil and so plants absorb these nutrients in the water they take in from the soil. The three main elements in mineral salts are:  nitrogen (N) – needed for healthy leaves;  phosphorus (P) – needed for healthy roots;  potassium (K) – needed for healthy flowers and fruit.1 of 208 of 24 © Boardworks Ltd 2004 2005
  • 9. Fertilizers and plant growth Plants take in mineral salts from the soil and in time there are less nutrients available in the soil. Farmers add chemicals called fertilizers to soil to make sure that their crops get enough mineral salts. Manufactured fertilizers can be expensive. So why do farmers choose to use them? Fertilizers help crops to grow well and so increase the farmer’s crop yield. What other types of fertilizer are there?1 of 209 of 24 © Boardworks Ltd 2004 2005
  • 10. Competition between plants Organisms that share a habitat have to compete with each other for limited living resources. A weed is any plant that is growing in the wrong place. Weeds are a problem for farmers as they compete with the crops for resources such as light, water, living space and mineral salts. How does competition affect the growth of crops?10of 201 of 24 © Boardworks Ltd 2004 2005
  • 11. Controlling weeds Weeds compete with crops for living resources and this can reduce crop yield. What can farmers do to control weeds? One way farmers can control weeds is to use chemicals called herbicides (or weedkillers). Weeds are part of the food web. How might using herbicides affect other organisms in the food web?11of 201 of 24 © Boardworks Ltd 2004 2005
  • 12. Contents 9D Plants for Food Plants as food Fertilizers and competition Pests and pesticides Summary activities12of 201 of 24 © Boardworks Ltd 2004 2005
  • 13. Pests and plant growth Pests are animals that eat and damage crops and so can be a problem for farmers. Pests reduce crop yield and compete with humans for food. What animals might be considered as pests by farmers?  Caterpillars are pests specific to a type of plant such as cabbages.  Snails and slugs are pests that eat the leaves of many plants.  Other common pests include insects, birds and mice. If the number of pests is reduced, what happens to crop yield?13of 201 of 24 © Boardworks Ltd 2004 2005
  • 14. Controlling pests What can farmers do to control pests? One method of pest control is the use of pesticides that kill pests. Pesticides contain poisonous chemicals called toxins. Pesticides can kill useful animals as well as the pests that they were meant to kill. Pests are part of the food web and the toxins in pesticides can affect other organisms in a food chain or food web. What are the advantages and disadvantages of pesticides?14of 201 of 24 © Boardworks Ltd 2004 2005
  • 15. Pesticide in a food chain Introducing a pesticide at the bottom of a food chain can have huge effects on the organisms above. Consider the following food chain from a lake: plant small large grebe plankton zooplankton fish fish (bird) A pesticide called DDT was sprayed on the lake to control mosquito larvae. DDT is a toxin that does not break down in the environment and so stays in animals’ bodies if it is eaten. The plant plankton at the bottom of the food chain absorbed some of the DDT from the water. How did this affect the rest of the food chain?15of 201 of 24 © Boardworks Ltd 2004 2005
  • 16. Pesticide in a food chain plant small large grebe plankton zooplankton fish fish (bird) DDT 5 ppm 10 ppm absorbed Each zooplankton ate lots of plant plankton and got several doses of DDT. Each zooplankton contained 5 ppm of DDT. Each small fish ate many zooplankton and so consumed even more DDT. How much DDT do you think each small fish contained? Each small fish contained 10 ppm of DDT.16of 201 of 24 © Boardworks Ltd 2004 2005
  • 17. Pesticide in a food chain plant small large grebe plankton zooplankton fish fish (bird) DDT 5 ppm 10 ppm 250 ppm absorbed Each large fish ate several small fish and so consumed even more DDT. How much DDT do you think each large fish contained? 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 contained?17of 201 of 24 © Boardworks Ltd 2004 2005
  • 18. Pesticide in a food chain plant small large grebe plankton zooplankton fish fish (bird) DDT 5 ppm 10 ppm 250 ppm 1600 ppm absorbed Each grebe had the amazing amount of 1600 ppm of DDT in its tissue which could kill the bird. In most cases, this amount of toxin made the birds’ eggs have very thin shells. These eggs broke very easily and so not many chicks were born alive. This example is actually based on real events that took place in the USA in the 1950s. It shows how a toxin can be passed on in a food chain and gets more concentrated at each step. This is called bioaccumulation.18of 201 of 24 © Boardworks Ltd 2004 2005
  • 19. Pesticide in a food chain DDT lead to the decline many species of birds. What do these pyramids of numbers show about the effect of spraying the lake with the toxin DDT on the numbers of organism in a food chain? before spraying after spraying grebe (bird) large fish small fish zooplankton plankton19of 201 of 24 © Boardworks Ltd 2004 2005
  • 20. Pesticide in a food chain DDT was considered as a safe pesticide when it was first used to kill insect pests. The problem was that DDT does not break down in the environment and the levels of this toxin that built up in top carnivores proved to be a major hazard. Today, many countries, including the UK, have banned the use of DDT to protect the environment. Alternative chemicals are now used as pesticides instead of DDT. These new pesticides break down quickly in the environment . Why aren’t these new pesticides hazardous to wildlife?20of 201 of 24 © Boardworks Ltd 2004 2005
  • 21. Contents 9D Plants for Food Plants as food Fertilizers and competition Pests and pesticides Summary activities21of 201 of 24 © Boardworks Ltd 2004 2005
  • 22. Glossary  competition – The demand by two or more organisms for limited shared resources, such as nutrients, space or light.  crop – A plant that is grown to be of use to humans.  fertilizer – A chemical that is added to soil to provide plants with the mineral salts needed for healthy growth.  herbicide – A chemical used to kill weeds.  pest – An animal that damages crops and competes with humans for food.  pesticide – A chemical used to kill pests.  toxin – A poisonous chemical.  weed – A plant growing in the wrong place that competes with a crop.22of 201 of 24 © Boardworks Ltd 2004 2005
  • 23. Anagrams23of 201 of 24 © Boardworks Ltd 2004 2005
  • 24. Multiple-choice quiz24of 201 of 24 © Boardworks Ltd 2004 2005