© 2009 Marshall Cavendish International (Singapore) Private Limited

Questions to think about… What is the source of energy for animals? How do plants get their food? How is the Sun related to our energy sources? © 2009 Marshall Cavendish International (Singapore) Private Limited

Source of energy for animals How does a meal provide us with energy? Let us follow a piece of baked potato’s journey in the human body. © 2009 Marshall Cavendish International (Singapore) Private Limited

1.In the mouth, the piece of potato is chewed into a mash. Saliva helps to digest the potato slightly. It is then swallowed. Source of energy for animals 2.The partially digested potato travels down the gullet to the stomach. 3.In the stomach, further digestion takes place. The potato is crushed and mixed with digestive juices. It then moves down to the small intestine. 4.In the small intestine, the potato is completely digested into a type of sugar called glucose. Glucose then enters the bloodstream and is transported to the cells in the body. © 2009 Marshall Cavendish International (Singapore) Private Limited

Source of energy for animals Energy is stored in food. The food that we eat cannot provide our bodies with energy immediately. It has to be digested first. Glucose is the digested form of food that provides us energy. © 2009 Marshall Cavendish International (Singapore) Private Limited

How do plants get their food? Plants need energy to stay alive. This energy comes from the food they make. Plants make food in the presence of sunlight, through the process called photosynthesis. During photosynthesis, energy from sunlight is used to combine carbon dioxide and water to make glucose and oxygen. Glucose, a form of sugar, is food for the plant. © 2009 Marshall Cavendish International (Singapore) Private Limited

How do plants get their food? Photosynthesis water + carbon dioxide glucose + oxygen in the presence of sunlight In this way, energy from the Sun is passed on to plants. © 2009 Marshall Cavendish International (Singapore) Private Limited

lettuce How do plants get their food? Many plants store starch temporarily in their leaves. Other plants store starch in their roots. Other plants store starch in their underground stems. carrots potatoes Excess glucose is converted to starch and stored in different parts of the plant. We get energy when we eat these plant parts. soy beans Some plants store starch in their seeds. © 2009 Marshall Cavendish International (Singapore) Private Limited

The Sun and our energy sources When plant parts are eaten by animals, the energy stored in the plant parts is transferred to the animals. Some animals eat plants only (plant-eaters) These plant-eaters get their energy from plants. rabbit giraffe zebra © 2009 Marshall Cavendish International (Singapore) Private Limited

The Sun and our energy sources Other animals eat plants and animals (plant-and-animal eaters). These plant-and-animal eaters get their energy from both plants and animals. chicken man raccoon © 2009 Marshall Cavendish International (Singapore) Private Limited

The Sun and our energy sources Some animals eat only other animals (animal-eaters). These animal-eaters get their energy from the meat they eat. tiger snake © 2009 Marshall Cavendish International (Singapore) Private Limited

The Sun and our energy sources Although animals that eat only animals do not eat plants, the energy that they get can be traced back to plants. Since plants make food from using energy from the Sun, the energy from the Sun is passed on from the plants to the plant-eaters. In this example, the energy from the grass is transferred to the plant- eater – the zebra. © 2009 Marshall Cavendish International (Singapore) Private Limited

The Sun and our energy sources Eventually, this energy is passed on from plant-eaters to animal-eaters. Here, energy is transferred from the plant-eater to the animal-eater, such as this lioness. Thus, food produced by plants become the source of energy for animals. © 2009 Marshall Cavendish International (Singapore) Private Limited