« Worms 2BIbDF09 10/11 » : différence entre les versions
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===flatworms or Platyhelminthes=== | ===flatworms or Platyhelminthes=== | ||
====Physical characteristic:==== | |||
They are flat and they can measure about 1mm to 20m in length. They have a single opening that serve them to eat and to defecate. They have no body cavities | They are flat and they can measure about 1mm to 20m in length. They have a single opening that serve them to eat and to defecate. They have no body cavities | ||
- Tapeworms | - Tapeworms | ||
Version du 10 janvier 2011 à 12:22
What is a worm ?
Worms are invertebrate animals. They are multicellular with true tissues and bilateral symmetry and they have a soft and flexible body. [They are protostomes.] They probably appeared at the beginning of cambrian era and they are an important step of animals' evolution. There are several Phyla and each one live in a specific environment. Some of them are parasitic organisms that can live in a body or just live in soil or in the sea.
What are the three main classes of worms ?
There are separate in three classes that depending on their body shape, there are three main classes of worms :
- flatworms or Platyhelminthes :
- Tapeworms
- roundworms or Nematoda
- Segmented Worms or Annelida :
- Earthworms - Polychaetes - Leeches
What are the characteristics of each one?
flatworms or Platyhelminthes
Physical characteristic:
They are flat and they can measure about 1mm to 20m in length. They have a single opening that serve them to eat and to defecate. They have no body cavities - Tapeworms
- roundworms or Nematoda - Segmented Worms or Annelida : - Earthworms- Polychaetes- Leeches