1, Overbreeding: All kinds of creatures on the earth generally have strong reproductive ability and tend to grow in geometric proportion.
2. struggle for existence: The struggle between biological and inorganic natural conditions, interspecific struggle and intraspecific struggle.
3. Genetic variation: The favorable traits retained by a species gradually mutate in the process of generation transmission, and a new species will be formed after the differentiation of traits and the disappearance of intermediate types.
4. Survival of the fittest: there are individual differences in the biological world. Under the pressure of survival competition, the unsuitable ones are eliminated.