IGCSE Biology Notes - General Characteristics and Classification of Arthropoda

Arthropoda is the largest phylum in the animal kingdom. the phylum  includes about 805 of the known animal species.. The phylum includes prawns, crabs, lobsters, cockroaches, scorpions, spiders, ticks, insects etc. Arthropods  are economically  of great importance to man. Animals like honey bees, silkworm moth etc, are beneficial. 

General Characters of Phylum Arthropoda

1. Arthropods are bilaterally symmetrical and triploblastic.

2. The body bears paired, jointed appendages and they are variously modified for different functions.

3. The body is covered with a thick chitinous cuticle forming an exoskeleton which is shed at regular intervals.

4. Compund eyes are present in most of the members

5. Respiration is by gills or book lungs or trachea

6. Excretion is by green glands or malpigian tubules.

7. Open circulatory system

8. The body is composed of many segments

Classification of Phlum Arthropoda

The phylum  is divided into different classes namely: Crustacea, Arachnids, Myriapods and Insects (BE4U Tips: CAMI)

Crustacea

• Crusta means hard shell
• More than 4 pairs of jointed legs
• Example: Prawns, Crabs, Lobsters

Arachnids

• Body divided into head cephalothorax
• 4 pairs of jointed legs
• Example of Arachids: Spider, Scorpion, Limulus, Ticks and mites

Myriapods :

• Many similar segments, each with at least one pair of jointed legs
• Example of Myriapods : Centipedes and Millipedes

Insects

• Body  divided into head, thorax and abdomen,
• 6 jointed legs attached to the thorax
• 4 wings attached to the thorax
• Example of insects: Cockroach, butterflies, grass hopper