LIFE ON EARTH
EVERY period and every locality has its particular flora and fauna, and when the environmental conditions change in any way, the forms of life also change. This is a fact which for anyone not ridden by prejudice is practically impossible to deny. Furthermore every living species exhibits those characters which are the most propitious for its continued existence in its particular environment. Aquatic animals assume certain forms and develop certain functions which are quite different from those in the land animals; plants which live in damp surroundings are of a particular pattern more or less, whilst those of the and deserts are quite different. Temperature, nourishment, warmth from the sun and degree of exposure, the concurrence of other living creatures and many other factors play their part in determining the growth of form and functions in everything that is alive.
It is inevitable that this should be so. If it be impossible to conceive of life without environment, if it be impossible for a creature to live in isolation, independent from all others, if life be an incessant replacement of substance and energy from the environment, the living creature takes from its environment what it needs and gives up thereto what it has a surfeit of; if life is the interrelation between the individual with everything that surrounds it, then it becomes easy to understand such environment as a decisive factor in the development of life. "Organism would be impossible of explanation without an environment" according to Child ( 1924). Each of the characters of an organism has its relation to external factors. This becomes still more evident when one considers the organism as a whole, which is what it really is. "Unity, order, physiological differences, relationships and the just adaptation of parts among themselves have no significance unless it be in relation to an outside world."
Correlation between form and function in a living creature and the conditions affecting it has always been a cause for wonder in those who study such things. Scientists may differ from one another in opinion in many respects, but the facts, outstandingly clear as they are, admit