→ Natural resources are finite, their size is constant except for seasonal variations.
→ Members of a population, though outwardly similar, show differences in characteristics.
→ Most of the variations are hereditary.
→ If this is the reality and if every organism reproduces at the maximum rate then theoretically the population will grow like explosives and it is equally true that realistically the population size is limited.
→ It means that there is competition for resources.
→ Some were able to survive and thrive at the expense of others, while some could not be promoted.