Wednesday, 24 August 2011

what is crab?


Crabs are 10-legged animals that walk sideways. There are almost 5,000 different species of crabs; about 4,500 are true crabs, plus about 500 are hermit crabs (hermit crabs don't have a very hard shell and use other animals' old shells for protection). Most crabs live in the oceans, but many, like the robber crab, live on land.

The Biggest Crabs: The biggest crab is the Japanese Spider crab (Macrocheira kaempferi), which lives on the floor of the north Pacific Ocean; it has a 12 ft (3.7 m) leg span. The biggest land crab is the Coconut crab (Birgus latro), which lives on islands in the Pacific Ocean; it has a leg span up to 2.5 ft (75 cm).

Diet: Many crabs are omnivores (plant- and meat-eaters), others are carnivores (meat-eaters), and some are herbivores (plant-eaters).

Anatomy: Crabs are invertebrates, animals without a backbone. They have an exoskeleton (also called a carapace), an outer shell that both protects them from predators and provides support. These crustaceans have ten jointed legs, two of which have large, grasping claws (called pincers or chelipeds). They have a flattened body, two feelers (antennae), and two eyes located at the ends of stalks.

Breathing: Marine crabs breathe underwater using gills, which are located in a two cavities under the carapace. True land crabs have enlarged, modified cavities that act like lungs so that the land crabs can breathe air.

Monday, 15 August 2011

characteristic of crabs and frog.


What is a Frog?

There are around 3,900 species of tailless amphibians, or Anura, also called Salientia, including the frog and toad.


Frogs are members of the zoological class called Amphibia.
Amphibians are cold-blooded (or poikilothermic) vertebrate animals. They differ from reptiles in that they lack scales and generally return to water to breed.
They are one of three types of Amphibians. Anura, also called Salientia, (frogs and toads), caudate (salamanders and newts) and caecilians (worm-like amphibians). 

Life Cycle of a Frog

True Love
Spawn (egg-mass)
Tadpole with legs
Young Frog, or Froglet