Question

In his epic work, On the Origin of Species, Charles Darwin uses the premises of variation, geometric and exponential growth, geological time, and extinction to arrive at his thesis of natural selection as the motive force of species origination. Explain. (Hint: Think Lyell, Malthus and, later, Mendel.)

Answer 1

Malthus was an economist who argued in his paper "an essay on the principle of population"that the growth rate of human population is greater than rate of food production. Unchanged growth inevitably leads to famine.

This argument of malthus gave birth to the first observation of darwin.

1. If all the organisms present in a population are undergoing reproduction and if the reproduction rate is sufficiently high and if the death rates are not equally high then the population will become enormous over geological time period.

2. Second observation of darwin talks about differences among individuals within organsims.

Everything that is existing today is different from what existed before. Everything that is present today has evolved from their respected ancestors which existed on the earth ages ago.

This is because individuals who possess traits that are more adaptable to the changes around them and has more reproducing capacity will dominate the individuals with traits that are less adaptable to the changes around them. This later category might become extinct.

3. Third observation of darwin deals with inheritance.

Offsprings acquire traits from their parents and resembles them.

According to mendelian's hypothesis offsprings gets traits from both their parents.

Hence progeny tend to be more adaptable to the changes than any one parent.

Darwin termed this capability of adapting more readily than others and this survival of the fitter as Natural selection.