Chapter 13, Problem 1CC

Summarize the key points of Darwin’s theory of descent with modification, including his proposed mechanism of evolution.

Summary Introduction

To summarize: The key points of Darwin’s theory of descent with modification including his proposed mechanism of evolution.

Introduction: According to Darwin’s theory of descent with modification, all life has descended from a common ancestral form as a result of natural selection. Individuals in a population have hereditary variations. The struggle of existence is the result of the overproduction of offspring in the face of limited resources. The individuals, who are suited more to their environment, leave more offspring as compared to other individuals and it leads to the accumulation of adaptations to the local environment in the population.

Explanation of Solution

The theory of evolution given by Darwin is still used as a powerful evidence for the theory. The main key point of the theory includes two observations and two interferences from natural selection are as follow:

• According to the first observation of Darwin, the members of a population were different in their inherited traits. The exact same phenotypes are not exhibited by the individuals in a population.
• The second observation was that many of the species are capable to reproduce or produce offspring if there environment is suitable for them for example: A fish lay 1000 eggs, only 500 hatch, 100 live to be juvenile, 20 become adult and only 5 were able to reproduce. So here the environmental factor is responsible for the less reproduction of individuals.

The two inferences are as follow:

• The more offspring were produced by the individuals whose inherited traits give them an advantage in survival and reproduction as compared to other individuals.
• The process of slight variations in inherited traits that were beneficial for survival or reproduction will increase representation from generation to next generation.