WORMS Coulter

CHARACTERISTICS OF WORMS

Biologists classify worms into three major phyla:

flatworms, belong to the phyla Platyhelminthes (plat ee hel minth eez)

Roundworms, belong to the phyla Nematoda

Segmented worms, belong to the phyla Annelida

BODY STRUCTURE

All worms are invertebrates Long narrow bodies without legs They all have tissue, organs, and body

system

NERVOUS SYSTEM

Worms are the simplest organism with a brain.

Because its brain and other sense organs are located in its head, it can detect objects, food, mates, and predators quickly.

Sense organs are sensitive to light, touch and vibrations pick up information from the environment.

FLATWORMS

Flatworms are flat and as soft as jelly. Many flat worms are parasites. Parasite is an

organism that lives inside or on another organism.

Parasites take their food from the host. Host is an organism in or on which a parasite lives.

Parasites may injure their host but rarely kill the host.

Some flatworms are free living, does not live in or on other organisms.

PLANARIANS

Free-living flatworms. They are scavengers (they feed on dead

or decaying material). They are also predators and will attack an

animal that is smaller. Feeds like a vacuum cleaner. Planarians glide onto their food, insert a

feed tube, inject the prey with digestive juices, then suck up the digested portion.

TAPEWORM

Parasitic flatworm Can get 10 to 12 meters long Tapeworms absorb food from the hosts

digestive system. Some tapeworms can live in human

hosts. Many tapeworms can live in more than

one host in its lifetime.

ROUNDWORMS

Roundworms have a digestive system that is like a tube, open at both ends.

A one-way digestive system is efficient. Its like a conveyer belt; start where food enters, nutrients are absorbed, then remaining is wasted.

This type of digestive system enables animal’s body to absorb a large amount of food.

SEGMENTED WORMS

Earthworms and other segmented worms have bodies made up of many linked sections called segments.

On the inside each segment has organs. For example each segment has tubes that remove waste.

Some organs are only found in certain segments. All segmented worms have a nerve cord and

digestive tube that runs the length of the body. They have a one way digestive system.

SEGMENTED WORMS

Circulatory system is closed. Much like the human body the blood

moves in a closed circulatory system.

EARTHWORMS IN THE ENVIRONMENT Earthworms tunnel for a living. During rainy days they come up out of the

ground to get leaves and other decaying matter that they will bring under ground and eat.

Earthworms obtain oxygen through moisture on its skin.

Earthworms help the soil in which plants grow. They burrow tunnels which allow air, water and plant roots to move through it.