Thirdly, the natural selection and the struggle for survival are two independent principles, and the struggle for survival is not a prerequisite for natural selection. At certain times in history, when resources were relatively abundant, the vast majority of organism's offspring can survive, and the natural environment still selected organisms. However, the result of natural selection may not be the evolution of organisms, and the inferior organisms can survive.

Therefore, the principle of natural selection of organisms should be modified as follow.

(1)The Principle of Natural Selection of Organisms:

Major premise: the condition that any organism can survive in nature is that the rate of reproduction of this organism is greater than or equal to the rate of death;

Minor premise: There are heritable variations among the offsprings of organisms; Some variations make organisms reproduce faster than other organisms, which is called having greater reproductive capacity; Some variations cause organisms to die at a slower rate than others, which is called as having greater survivability. The variation with greater reproductive ability and greater survival ability is the superior variation, and the opposite variation is the inferior variation.

Conclusion: The inferior variation is easy to be eliminated, the superior variation is easy to survive and leave to the offspring.

(2)The Principle of Biological Survival Struggle.

Fact 1: Survival resources are limited;

Fact 2: Biological fertility is excessive;

Conclusion: Most of the offspring of living things must perish.

The two facts here are both minor premises, the major premise is that living things must perish when they do not have enough resources to survive. By perish, I mean the inability to reproduce. Overreproduction makes the survival of organisms very competitive, the rate of death is very high, so that only a few of the most superior organisms can survive. The result of the combination of survival struggle and natural selection is biological evolution, that is, the conclusion of the principle of natural selection is the major premise, the principle of survival struggle is the minor premise, and the following biological evolution principle is concluded.

(3)The Principle of Biological Evolution:

Major premise: The inferior variation is easy to be eliminated, and the superior variation is easy to survive and leave to the offspring.

Minor premise: The vast majority of the offspring of organisms must perish;

Conclusion: The inferior variations of organisms must be gradually eliminated, and the superior variations can survive and be left to the offspring.

The so-called biological elimination refers to the complete extinction of a certain structure of organisms. Survival and elimination are directly related to the number of organisms, not directly related to the reproduction rate and death rate. When an organism mutates, it directly affects the rate of reproduction or death, not the number of organisms. When the rate of reproduction is less than the rate of death, organisms may survive for a long time, but if this speed difference is maintained, organisms will inevitably become extinct. Therefore, natural selection of organisms must be linked to the rate of reproduction and death.