2. WHAT IS PHOTOSYNTHESIS?

3. Animals get their energy from the food they eat through the process of respiration with the help of the digestive system, the respiratory system and the circulatory system. This energy is required to carry out life processes and to survive. However, since energy cannot be created or destroyed, the energy released from the food that animals eat must have been converted from other forms of energy. WHAT HAVE WE LEARNT SO FAR?

4. So we take a closer look at the food animals eat. Animals eat either plants or other animals. However, by tracing food chains, which show a series of living things linked together whereby each one is the food for the next, we realise that animals ultimately get their food from plants. Therefore, the ultimate source of food for animals is plants and energy transfer among organisms begins from plants. WHAT HAVE WE LEARNT SO FAR?

5. Where do plants get their energy for their life processes from? Plants do not eat food. They make food and then get their energy from the food that they make again through respiration. When they make food, they convert light energy from the sun to stored/chemical energy in the food. This process is known as photosynthesis. WHAT HAVE WE LEARNT SO FAR?

6. Photosynthesis is the process by which plants make food in the presence of sunlight. What do the plants need when carrying out photosynthesis? Sunlight, water, carbon dioxide What do the plants produce in the process? Food and oxygen PHOTOSYNTHESIS

7. So, what would the equation for the process, photosynthesis be? Should it be : –Sunlight + water + carbon dioxide food + oxygen Sunlight is not matter. It is energy. Can it be an input? It should be –Carbon dioxide + water Food (glucose) + oxygen PHOTOSYNTHESIS – The equation sunlight chlorophyll

8. Why is it that only plants can carry out photosynthesis? Plants have chloroplasts which contain chlorophyll. Animals do not have. Chlorophyll is required to trap energy from the sun. What exactly happens during the process to make the input become the output? Firstly, the reactions carried out during photosynthesis is powered by the energy trapped by the chlorophyll. PHOTOSYNTHESIS – The equation

9. Water molecules (H 2 O) are split apart into hydrogen and oxygen atoms. These combine with carbon dioxide molecules which is CO 2 to make glucose (C 6 H 12 O 6 ). Oxygen gas is given off as a waste produce. Therefore the chemical equation for the above reactions is 6CO 2 +6H 2 O C 6 H 12 O 6 +6O 2 PHOTOSYNTHESIS – The chemical equation sunlight chlorophyll

10. PHOTOSYNTHESIS – A Glucose Molecule

11. Where does photosynthesis take place? Any part of the plant which contains chlorophyll. However, the leaves are especially adapted to make food. In cactus, the leaves are spiny, not much chlorophyll hence its stem do the job. PHOTOSYNTHESIS –Where does it happen?

12. Leaves have external and internal features that help them carry out photosynthesis. –Leaves have large surface areas and spread out in such a way they do not overlap so that they absorb the maximum amount of sunlight. –Cells usually have a large number of chloroplasts. –They have a network of veins which help transport water from the stems to all parts of the leaf and then transport glucose from the leaves to the stem to all parts of the plant. PHOTOSYNTHESIS – Why are leaves the ideal place for photosynthesis to happen?

13. Leaves have external and internal features that help them carry out photosynthesis. –They have special pores mainly on the underside of the leaf called stomata which allows carbon dioxide from the air to enter the leaf and oxygen to be released into the atmosphere. –Leaves are also thin to allow quick diffusion of carbon dioxide to all the cells in the leaf. PHOTOSYNTHESIS – Why are leaves the ideal place for photosynthesis to happen?