The Arthropods

1- They have a hard skeleton made of chitin and protein.

2-They have jointed  appendages to provide movement.

3- Aquatic arthropods
    respire using gills
  Terrestrial arthropods, (insects) respire by a special system of channels : Tracheae

4- Arthropods have an
Open Circulatory System.

5- The body is generally made of three segments; a head, a thorax and an abdomen.

Flying arthropods have a pair of wings that start out  from the thorax.

6- Some arthropods have antennae as sensors for sounds, smell and taste.

The nervous system of arthropods is well developed compared with the other organisms.

7- The reproductive phase of
arthropods has the
following stages;
egg, larva, pupa
and adult.

almost all are aquatic organisms and have

gills for respiration. They have a hard

 skeleton which covers their body.

 Examples :
lobsters, crayfishes, crabs and shrimps.

 some of them are microscopic such as daphnia and

Cyclops.

Arachnids have four pairs of appendages. They have toxic glands and some of them are poisonous.

Examples of arachnids are spiders, scorpions, ticks and mites.

Centipedes have about 35 legs whereas millipedes have about 300 legs.

Generally they have three pairs of appendages and two pairs of wings.

Some of the insects such as ants, bees and termites form societies.

Well known examples of insects are bees, termites, butterflies, grasshoppers.
Most insects are terrestrial organisms.