1. Energy in food
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2. Questions to think about…
How do plants get their food?
How is the Sun related to our energy sources?
What is the source of energy for animals?
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3. Source of energy for animals
Let us follow a piece of baked potato’s journey in the human body.
How does a meal provide us with energy?
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4. Source of energy for animals
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.
In the stomach, further digestion
takes place. The potato is crushed
and mixed with digestive juices.
It then moves down to the small
intestine.
The partially digested potato
travels down the gullet to the
stomach.
In the mouth, the piece of
potato is chewed into a mash.
Saliva helps to digest the potato
slightly. It is then swallowed.
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5. 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.
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6. 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.
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7. 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.
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8. How do plants get their food?
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
Many plants store starch temporarily in their leaves.
Some plants store starch in their seeds.
Other plants store starch in their roots.
Other plants store starch in their underground stems.
lettuce
potatoes
carrots
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9. The Sun and our energy sources
rabbit
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.
giraffe
zebra
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10. 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.
raccoon
man
chicken
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11. 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.
snake
tiger
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12. 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.
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13. 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.
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14. The end
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