Write four distinctive characters of Mammalia.

When we try to define 'living', we look for certain distinctive characteristics of living organisms. Mention four such features.

State four characteristics of Laser.

Write any four characteristics of Pteridophytes.

Write four differences between animals of Cnidaria and Ctenophora.

Write any four differences between Chordates and non-chordates.

Write four differences between the animals of Platyhelminthes and those of Aschelminthes. Give an example of each.

Why the metallic character of alkali metals increase down the group?

What is dual character of light?

Write the four force in nature.