Charles Darwin and the Struggle for Survival

Charles Darwin, who lived from 1809 to 1892, is responsible for the theory of evolution, the idea that all organisms adapt to their changing environment and over time can modify in their appearance, physiognomy and internal makeup. But before describing the process of evolution, he wrote about the struggle for survival that all creatures go through. The struggle for survival is central to understanding the concept of evolution. In fact, Darwin says that it is important, but sometimes difficult to bear it in mind.

This struggle takes two forms: the perpetuation of the individual and its progeny. The grass plant, horse, mouse eared bat and ivy possess an internal force to themselves endure. They also spend much of their existence reproducing offspring. The effort to survive individually and in progeny is common to all organisms (ignoring for the moment that humans can commit suicide.)

Darwin says that in nature there is an ongoing ebb and flow of creation and destruction. Organisms produce seeds, offshoots and young and other forces destroy much of what is produced. These other forces can be similar organisms competing for the same resources, predators, or adverse weather. For example, oak trees produce hundreds of acorns but most of these are eaten by animals or fail to thrive because the soil they fall on is not fertile. Birds lay numerous eggs which are eaten by rodents or other birds. And even if the eggs hatch, the chicks are in danger of becoming the prey of foxes, wolves or hawks.

Some creatures produce high numbers of potential offspring and other creatures small amounts. For example, rabbits, mice, mosquitoes, dandelions, and oak trees have the potential for generating vast numbers of successors. Elephants on the other hand, according to Darwin (and I have no independent knowledge about this) produce about three calves in their 90 years of life.

Left to their own devices and in the absence of adverse factors, organisms would spread over an entire region propagating geometrically. If there are no predators and resources are abundant and the environment (chiefly the weather) is favorable then an organism will multiply and reach high numbers in a short time. This has been observed over and over again as when a plant of animal is introduced into another continent where there are no predators to keep the number down.

The only factor that would inhibit the unlimited spread of the organism is the other members of the species competing for resources—fertile soil, water, prey, food plants,
etc.

Whether a creature produces high numbers of offspring or small amounts is not a good predictor of how many of the species will survive. Normally those organisms that generate great amounts of potential successors will experience vast destruction of the progeny. Most acorns are eaten by animals of the forest. And those who create just a few new members of the next generation will see them all survive. Elephants have few if any predators.

With this ongoing clash of creation and destruction in living things, it is easy to see that any small variation in the structure or physiognomy of a plant or animal that allows it to avoid its demise will be favored. White butterflies are more easily spotted by birds and eaten while dark butterflies may avoid detection. Swifter deer will outrun the wolf and the slower ones will not. These favorable variations will be passed along to future generations of the species in greater proportion because these organisms survive in greater percentages. Those without these favorable variations will survive in smaller shares of the whole.

It is this gradual changing in any species toward the favorable variations and the ultimate disappearance of those with detrimental variations that Darwin calls Natural Selection. The continuous change in organisms toward characteristics that allow them to survive predators, competition with others of the same species, and scarce resources is called Evolution.