The greatest of the phylums!!!

Stefani M.Simeon N.Anand P. Pat P.Eric T.

Arthropoda

Germ LayersSince arthropods are a higher form of life than the flatworms, they develop with three germ layers. The germ layers are formed while they are developing in the embryonic state.

SymmetryArthropods have bilateral symmetry. So arthropods are usually symmetrical when divided down the center. Some however, do not have bilateral symmetry. For example, the barnacle is considered to be an arthropod and yet it does not have bilateral symmetry.

CoelomArthropods are considered to be coelomates because they are triploblastic.

Coelem is the cavity sack inside the plant that provides structural support as well as protection for the internal organs and pathways.

Digestive Tract

• The arthropods are protostome animals in their embryonic development. They have tube like digestive tracts that start from the mouth and end in the anus. The blastopore originates the mouth.

Cephalization

• Arthropods have cephalization. This is present when one looks at the heads of arthropods that justify this fact.

SEGMENTATION

• Arthropods are usually segmented A good example would be insects. Their bodies are segmented into three parts. Head, thorax and abdomen. The lobster also has a similar design

Skeleton and Appendages

• Arthropods have an exoskeleton• They usually have 3 plus

pairs of joint appendages.

CIRCULATORY SYSTEM

• In most arthropods circulation is provided by a heart that runs the length of the back/thorax. This means that they have an open circulatory system

Respiratory System

• Three different methods:– Aquatic species have gills– Land arthropods have

internal surfaces for gas exchange

– Insects have tracheal systems, branched air ducts leading into the interior.

Reproduction

• Most rely on sexual reproduction.

• Aquatic arthropods may breed by external fertilization.

• May lay eggs

Habitat

Aquatic habitats• Ponds, pools, puddles

Ground habitats

Plant habitats

Woodland habitats

fields