The Open Door Web Site
Part XVIII: Energy and Activity : Feeding, Breathing and Activity Index
School children, Iquitos, Peru
ENERGY AND ACTIVITY
Feeding, Breathing and Activity
The energy in food is used to carry out all the activities that keep an organism alive. For example: moving, keeping warm or sensing changes in the world around it.
The more active an animal or a plant is, the more energy it needs to stay alive.
Energy is measured in Joules or sometimes in calories. The table opposite shows how much energy a man uses when he is involved in different activities. You can see from this table that the activities that need the most effort also need most energy.
Animals obtain the energy that they need from the food that they eat and green plants make their energy-containing food using sunlight energy.
Fungi are non-green plants; they get their energy from the dead bodies that they decompose.
Therefore, in the living world there are two possible sources of energy: sunlight or the bodies of other organisms. The green plants which use sunlight energy are called autotrophs (this comes from the Greek words auto = self, and trophos = feeding). The animals and fungi which feed on other animals and plants are called heterotrophs (this is also from Greek words which mean "feeding on others").
Not all the food in our diet contains the same amount of energy. Some foods are rich in energy because of the chemicals that they are made of. Foods which are rich in sugar, fat or protein contain a lot of energy. Opposite is a table which shows how much energy there is in foods which you may eat. You can see that the foods rich in fats and oils contain most energy.
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