Phylum Arthropoda

• It is the largest phylum of the Animalia.
• It includes insects, spiders, crayfish, etc.
• Level of organization - They have organ-system level of organization.
• Body symmetry - They are bilaterally symmetrical.
• Body wall - triploblastic, segmented. Coelomate animals.
• The body of arthropods is covered by chitinous exoskeleton.
• Body is divided into head, thorax and abdomen.
• Jointed appendages - arthros - jointes, poda - appendages, hence the name is derived from this characteristic.
• All the arthropods have jointed appendages which give arthropods a wide range of controlled motions.
• Respiration is through organs like gills, book gills, book lungs or tracheal system.
• Circulatory system - It is of open type.Sensory organs are present, antennae, eyes (compound and simple), statocysts or balance organs are present.
• Excretion - It takes place through malphigian tubules.
• Mostly they are dioceious. Fertilization is usually internal.
• They are oviparous animals.
• Development may be direct or indirect.
• Examples: Honey bee, Silkworm, Lac insect, Mosquitoes, Locust, Crab
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