Flatworms Science Investigation

By Shannon, Emily and Brian.L

Flatworm Introduction

The First Flatworms

The first flatworms, probably evolved from something like a hydra (the Genus, not the mythical Creature) about 550 million years ago. Like all other living things at that time, early flatworms lived in the sea, but now most species prefer shallow water.

Appearance and Behaviour

Flatworms are invertebrates, they have no skeleton in their body. They have tiny bristles called cilia which help them move faster. They have got 3 cell layers in total, which are the endoderm, the mesoderm and also the ectoderm. (Diagram 2 below)


Although the flatworms are flat and look really simple, they have some advanced bodies structures compared to some other animals.


Flatworms don't have a respiratory system or circulatory system, but they do have a really cool little digestive system. Many species of flatworm uses a mouth to eat, however most species of flatworms have no Anus (butt). The problem with no anus is that the stuff you don't digest goes out the mouth when you're done.

Prey and Predators

Most flatworms eat protist, rotifers, nematodes, small crustaceans, aquatic worms, dead animals and more. Sometimes they also eat flatworms including their own kind.


However they have just as much predators, for example, tadpole, crustaceans, small fish and aquatic insects including dragonfly naiads, diving beetle and others.

Common Types of Flatworms

The Tapeworm

Tapeworms are flatworms that live in a person's Digestive system. They can grow to more than 10 meters and live as long as 25 years. Tapeworms get into the body when a person eats or drinks something that has a worm or Tapeworm eggs. Once it's inside the body, The tapeworm feeds off the food that the person is digesting. It uses this nutrition to grow

Procotyla Fluviatilis

This is a kind of a flatworm that can grow up to 20 millimeters long, with brown or greenish body. When they are newly born they can be 1~3 millimeters long.


They can be found in shallow waters in pond, lake, stream. To travel to different parts of water they can move by following the stream or they can migrate by larger animals.