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How plants works


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  • 1. Gr 9 Second termHow plants work
  • 2. Plants produce there own food (glucose) by photosynthesisCarbon dioxide + Water(+ light energy) Glucose+Oxygen [ in the presence of chlorophyl]
  • 3. Plants: Light energy  potential energy Animals get energy from plantsPredators and othermeat eating animals gettheir energy fromanimals that originallygot it from plants.
  • 4. PhotosynthesisCarbon dioxide +Water(+ light energy)Glucose + Oxygen Energy is taken up during photosynthesis. It is therefore an example of an endothermic chemical reaction.
  • 5. Functions of plants:Plants supply food tohumans and all other animals.Plants remove carbon dioxidefrom the atmosphere.Plants release oxygen to theatmosphere.
  • 6. Many medicines are made from plantsWood from plants areused to make furnitureand to build houses. Wood is used as a fuel. Plants supply shelter/habitat to animals.
  • 7. Parts of the plant roots stem leaves Flower / fruits
  • 8. Functions of the organs of a plant:Roots a) Root hair cells absorp water and minerals from the soil. b) Roots anchor the plant in the soil.
  • 9. Stemsa) Keep the plant up straight for sunlight to reach the leaves.b) Stems contain small tubes that transport water and dissolved minerals (called xylem) from the roots to the rest of the plant and food (transported in phloem) from the leaves to the rest of the plant.
  • 10. Leaves-Leaves are specialised organs for photosynhesis.They produce food (simple sugars/glucose)that the plant needs for it’s life processes (MRS GREN).Leaves are green becausethe cellscontain a molecule or colourpigment called chlorophyll (in the chloroplasts).
  • 11. The palisade cells are specialised cells for photosynthesis.They are found in the top layer of a leaf.The xylem, whichtransports water anddissolved minerals and the phloem, whichtransports foodaround the plant,form the veins of a leaf
  • 12. Stomata are little holes which are found mainly onthe bottom of a leaf. Exchange of three gassesnamely carbon dioxide, oxygen and water vapourtakes place through the stomata.
  • 13. FlowersSpecialised organs for reproduction. They containboth male (anthers) and female (carpel)parts that are responsible for sexual reproduction inplants.
  • 14. What do plants need to grow well?Seeds need oxygen, water and warmthto germinate. Plants need carbon dioxide, water, sunlight, soil with a specific pH and minerals ( such as phosphates, potassium, nitrogen and magnesium) to grow well
  • 15. Farmers and gardeners add fertilizers or compost tothe soil to supplement the amount of minerals. Theuse of too many fertilizers can damage theenvironment. We call this process eutrophication.
  • 16. The burning of fossil fuelsresult in the release of sulphurdioxide and nitrogen oxide.These two oxides react withthe water in rain drops toform sulphuric and nitric acid.As a result of this the pH ofrain drops and the rainbecomes very acidic. It can beas acidic as vinegar. Acid rainis harmful to metal, soil, stoneand plants.
  • 17. What happens to the glucose (sugar) that is made duringphotosynthesis?As previously said, glucose(sugar) is made duringphotosynthesis. The plant uses it for it’s own lifeprocesses.The phloem transports it through the plant. Excessglucose is binded together to form starch.The starch is stored in the plant, mainly by theroots.Starch in a photosynhesising plant can already bedetected in the leaves.
  • 18. Test for starch Method ReasonStep 1: Put a leaf To break downin boiling water for the cell walls soabout 5 chemicals canminute, until it is enter the cell.soft. To remove the greenStep 2: Put pigment (chlorophyl).the leaf in a This is for us, to moretest tube clearly see a colourwith ethanol change when wefor a while. add iodine.
  • 19. Test for starch Method Reason To make it soft Step 3: Rinse the again. leaf in water.Step 4: Spread the To stain anyleaf out on a white starch, iftile/saucer/petri present. Turnsdish. blue/black if starch isStep 5: Drop a few present. Staysdrops of iodine on yellow/brownthe leaf if no starch is present.
  • 20. A leaf covered with iodine turns black dueto the presence of starch
  • 21. Is light needed for photosynhesis?If plants are kept in a dark cupboard for longer than24 hours they do not have anymore stored starch intheir leaves. The starch is broken down into sugar.The plant uses the sugar for it’s own life processes(MRS GREN).
  • 22. Plan an investigation to determine if sunlight is needed for photosynhesis. Aim of the investigationTo determine if sunlight is needed for photosynthesis.
  • 23. A. The planning of an investigation consists of thefollowing steps:a) Find the variables.b) Formulate a hypothesis for the investigation.c) Write down the method, step-by-step, that you are going to follow.d) How are you going to record your results?e) Which safety measures will you have to keep in mind?f) What do you predict (think) your results are going to be? Explain your answer by using scientific knowledge.
  • 24. Is oxygen released during photosynthesis?
  • 25. a) What are the variables in this investigation?b) Formulate a hypothesis for the investigation.c) Write down the method, step-by-step, that they are going to follow.d) How do we know that the gas released is oxygen?e) Why is the release of oxygen during photosynthesis so important?f) Study the above figures. Write down the results and the conclusion for this investigation.
  • 26. Water in plantsPlants need water for :a) Transport of substances to and through the plant.b) Cooling down the plant.c) Supporting the soft parts, to keep them firm and upright.
  • 27. d) Photosynthesise) Chemical reactions in the plant cells.
  • 28. Water enters the plant through the specialised root hair cells.It moves through the roots, stems and leaves in the xylem.Water evaporates from the surface of the leaf through thestomata. This type of evaporation from the leaves is calledtranspiration.
  • 29. Adaptations of plants to reduce the loss of water:a) Closing of the stomata: At night or at times when it is very hot, windy or dry.b) Waxy layer on top of the leaf: Serves as a waterproof layer to minimise evaporation. Eg. Succulents
  • 30. c) Hairs on the leaf: The hairs trap a layer of moist air against the leaf.d) Stomata are situated at the bottom of a leaf: This reduces evaporation/transpiration from the leaf.e) Reducing the surface area of the leaf: To reduce evaporation E.g. Cactus thorns are rolled up leaves. Leaves of plants in warm areas tend to be small while leaves that grow in the shade are big.