1. Unit 3
INVERTEBRATES

2. INVERTEBRATES
Are animals which do not have a skeleton
Size Most are very small, some such as giant squids
Body shape Most invertebrates are symmetrical but some
have irregular bodies.
Body covering Many bodies are protectec by shells or
exoskeletons
In the sea
In fresh water
On land
The invertebrates live
Can move
Attach themselves to rocks or the sea floor
Parasites: Live inside other animals
Are oviparous
Invertebrates

3. INVERTEBRATES GROUPS Sponges Have irregular bodies. They cannot move
Cnidarians Have jelly-like bodies. They have tentacles
which can sting you.
Worms Have long, sofl bodies. Some are cylindrical, and others
flat. Many are parasites.
Echinoderms Are symmetrical. They have a skeleton made up of
hard plates.
Arthropods Are covered by a hard exoskeleton. Some are aquatic.
Molluscs Have a soft body. Many are covered by one or two shells

4. ARTHROPODS Arthropods have an external exoskeleton
Made up of many small plates
The exoskeleton is rigid.
From time to time the Arthropods sheds it ,and
grows a new ,flexible one.
As a result arthropods grow
ARTHROPODS GROUPS
INSECTS Insects body is divided in three parts.the thorax
has six legs
ARACHNIDS Have eight legs . Body divided in abdomen and
cephalothorax
CRUSTACEANS Have ten or more legs . Body divided in abdomen
and cephalothorax
MYRIAPODS Have long bodies with many legs. The head has one
pair of short antennae.