eyes (compound and simple), statocysts (organs of balance/ equilibrium) are present. Excretion takes place through malpighian tubules , green glands , coxal glands , etc. They are mostly dioecious and oviparous; fertilization is usually internal. Development may be direct or indirect.
Life history includes many larval stages followed by metamorphosis. Examples : Limulus (King crab, a living fossil), Palamnaeus (Scorpion), Eupagarus (Hermit crab), Apis (Honey bee), Musca (House fly), Vectors- Anopheles , Culex , Aedes (mosquitoes), Economically important insects - Apis - (Honey bee), Bombyx (Silk worm), Laccifer (Lac insects), Gregarious pest - Locusta (Locust) (Figure . ) Spider silk is five times stronger than steel of the same diameter. It has been suggested that a Boeing could be stopped in flight by a single pencil- width strand and spider silk is almost as strong as Kevlar, the toughest man-made polymer.
Figure . Examples of Arthropoda Prawn Hermit crab Locust Scorpion Spider Limulus (Living fossil) XI Std Biology-Zoology Chapter- respiratory pigment. They are dioecious and oviparous. Development is indirect with a veliger larva (a modified trochophore larva).
Examples: Pila (Apple snail), Lamellidens (Mussel), Pinctada (Pearl oyster), Sepia (Cuttle fish), Loligo (Squid), Octopus (Devil fish) (Figure . ). Figure . Examples of Mollusca Pila Octopus Squid Oyster Marbled Cone Snail ( Conus marmoreus ) This cone-shaped snail can deliver dangerous venom which may result in vision loss, respiratory failure, muscle paralysis and eventually death.
There is no anti-venom available. . . Phylum Echinodermata (G .
Echinos – spiny; dermos –skin) All Echinoderms are marine animals. The adults are radially symmetrical but the larvae are bilaterally symmetrical . These animals have a mesodermal endoskeleton of calcareous ossicles and hence the name Echinodermata (spiny skin). They are exclusively marine with organ system level of organisation.
The most distinctive feature of echinoderms is the presence of the water vascular system or a mbulacral system with tube feet or podia , which helps in locomotion, capture and transport of food and respiration. The digestive system is complete with mouth on ventral side and anus on the dorsal side. Excretory organs are absent.