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Earthworm:
1. It takes dead matter into the soil, loosens the soil (aerates the soil / makes it possible for gases and water to enter the soil), serves as food for other animals.
2. The outer covering is moist and soft for respiration. The body therefore dries out very easily and respiration cannot take place through the dried-out skin.
3. It can kill animals like earthworms. This will result in the soil becoming hard and dry and water, gases and dry material will not enter the soil: the soil will become infertile.
The earthworm is part of a group that is known as segmented worms.
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It is important that you get to know the earthworm, as this small animal plays a very important role in the ecosystem.
Let us look at how its body is adapted to its way of life.
The earthworm is approximately 150 mm long and the whole body consists of ring-shaped segments, each approximately 1 mm thick.
At the front tip there is a mouth with a small lip with which food is pushed into the mouth. At the back tip is the anus, where the remains of the food leave the body.
On all the segments, except the first and the last, there are hairs that help the worm to move through the soil.
The earthworm moves by means of muscles in the segments that contract and relax, causing the body to become long and thin, and then short and thick. The hairs on the segments press against the soil and the worm then moves forward.
The earthworm comes out of the ground at night and pulls rotting plant material into its tunnel with the help of the lip in front of its mouth. It also eats the soil as it tunnels through the ground.
Respiration
The earthworm breathes through its moist skin. It therefore is important that the skin remains moist, as the worm is dependent on a moist environment.
The earthworm has a complex system of tubes in its body with openings to the outside by which it controls the quantity of water that its body absorbs and excretes so that the correct balance is maintained.
Two earthworms lie next to one another and exchange sexual cells. A slime cocoon forms around their bodies and the sexual cells remain in the cocoon when it slips off the bodies. The young hatch in the cocoon and immediately look just like their parents.
In summary: the earthworm in the ecosystem
1. The earthworm plays an important role in the ecosystem because it … (give two reasons)
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2. The earthworm is dependent on a moist environment because _________________
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3. If we use poison to combat pests, it can be disadvantageous to the soil because
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Learning Outcome 2:The learner will know and be able to interpret and apply scientific, technological and environmental knowledge.
Assessment Standard 2.1: We know this when the learner recalls meaningful information (at least definitions and complex facts);
Assessment Standard 2.3: We know this when the learner interprets information.
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Last edited by Siyavula User on Mar 5, 2009 6:36 am -0600.