Why are human beings who look so different from each other in terms of size, colour and looks said to belong to the same species ?

Why do they differ from each other ?

Why are the different parts of birds different from each other ?

Cyanobacteria and heterotrophic bacteria have been clubbed together in Eubacteria of Kingdom Monera as per the five kingdom classification, even though the two are vastly different from each other. Is this grouping of the two types of taxa in the same kingdom justified ? If so why?

How do rods and cones of human eye differ from each other chemically and functionally?

Think why ancient human beings travelled from one place to other and how they travelled.

Find the number of ways in which 5 red balls, 4 black balls of different sizes can be arranged in a row so that no two balls of the same colour come together.

The number of ways in which 4 red roses , 4 white roses of different sizes can be made out to form a garland so that no two roses of the same colour are to come together is

The number of ways in which 5 red balls , 4 black balls of different sizes can be arranged in a row so that no two balls of the same colour come together is