WORMS
Worms are invertebrates. Three kinds of worms are flatworms, roundworms
and segmented worms.
Roundworms
 have round tube-like bodies
 have two body openings; At one end, food is taken in and at the other
end, waste is passed out.
 have a nervous system with a brain and other sense organs.
 have bilateral symmetry (they are exactly the same on both sides of
the body).
Roundworms, also called nematodes, can be found everywhere – in the
soil, sea, fresh water, on plants, in animals (including humans), and even in
the air (when in the egg stage). Non-parasitic roundworms are beneficial
(helpful) to the environment because they act as decomposers by recycling
decaying, rotting organic matter, and reducing them to a form suitable for
intake by plants. Without them, the energy supply to plants and animals
would be greatly reduced.
Roundworm
Some roundworms are herbivores (eating plants and algae), but some such as pinworms and hookworms - are parasites.
Parasites are organisms that live in or on other organisms (hosts), and
feed off them without helping them in any way. Parasites are often harmful
to their hosts. Humans can become infected with parasitic nematodes if
they eat meat that has not been properly cooked.
Flatworms
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have a flattened body
have a triangular-shaped head and eye spots on the head
have a digestive system
have a simple nervous system
have one body opening; they have no anus, so waste is excreted
through the same opening that takes in food
 regrow parts (regeneration); If a planarian is cut into two pieces, the
head part will grow a tail and the tail part will grow a head.
Planarians, tapeworms and flukes are all flatworms.
Tapeworms
The tapeworm is a parasitic flatworm that has a long, flat body made up of
a head, a neck, and a chain of segments (or sections). A chain can consist
of 3 to more than 4 000 segments, and range in length from less than one
inch (2.5cm) to more than 75 feet (23m). Adult tapeworms live in the
intestines of vertebrate animals, including humans. They lay eggs in the
digestive system of the host (the infected animal). If these eggs burrow
themselves into tissues in our brains, hearts or kidneys, they will kill us.
Flatworm
Segmented Worms
 have bodies divided into many little segments (sections), like rings
joined together
 have body parts for the nervous, digestive, excretory and circulatory
systems repeated in each segment between the mouth and the anus.
(This allows the worm a better chance to survive - by regeneration - if
part of its body is cut off.
 have two body openings
 have bilateral symmetry
The earth worm and leech are two types of segmented worms. The leech is
a parasite which sucks blood. The earthworm lives in the soil. It makes the
soil soft, and also enriches the soil with its waste, which comes from the
dead leaves that it eats.
Earthworm