Science Define :

If the union of male and female gametes takes place outside the bodies of both organisms, then the fertilization is called as external fertilization.

The multicellular animals which do not have body cavity are called acoelomate.

The animals which can live in water as well as on land are called amphibians.

The animals which have both, male and female reproductive systems in the same body are called hermaphrodites.

The multicellular animals which have three germ layers, namely ectoderm, mesoderm and endoderm, formed during initial period of their embryonic development are called triploblastic animals.

The multicellular animals which have two germ layers, namely ectoderm and endoderm that are formed during initial period of their embryonic development, are called diploblastic animals.

The animals which have dorsal, supporting notochord in their bodies are called chordates.

The animals which can maintain their body temperature constant irrespective of surrounding temperature are called warm blooded animals or homeotherms.

The long, rod like supporting structure present on dorsal side of an animal body is called notochord.

Formation of groups and sub-groups of animals depending upon similarities and differences among animals is called as animal classification.