Kingdom Animalia - Phylum - Arthropoda - (Organisms with Jointed Legs) | 9th Science : Living World of Animals - Diversity in Living Organism - Kingdom Animalia
Chapter: 9th Science : Living World of Animals - Diversity in Living Organism - Kingdom Animalia
Phylum - Arthropoda - (Organisms with Jointed Legs)
Phylum - Arthropoda - (Organisms with Jointed Legs)
Arthropod is an ancient and largest phylum with
more than 9,00,000 species. The word Arthropod means ‘jointed legs’. Insects, spiders, crabs, shrimps, butterflies,
millipedes, centipedes and scorpions belongs to this phylum. The body plan is
distinct with segmentation − head,
thorax and abdomen . The
exoskeleton is made up of chitin. As
the size of exoskeleton cannot change during growth the animals has to shed it
periodically by a process called moulting.
The coelomic cavity is filled with haemolymph(blood). The haemolymph circulates
through the body cavity. They do not have well defined blood vessels. This is
called open circulatory system
wherein the tissues and cells of the animal body are bathed directly in blood.
Small arthropods directly absorb oxygen through
their body surface. Many of the larger aquatic species breathe through feathery
book gills and many land arthropods
breathe through a system of tiny body tubes called tracheae. Excretion occurs through malphigian tubules and green
glands.
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