Chapter 21, Problem 1DA

Suppose that a male with a beak depth of 10 mm mated with a female with a beak depth of 8 mm. What would the expected beak depth of the offspring be? Would it matter if the female’s beak was 10 mm and the male’s 6 mm?

Summary Introduction

To determine: The expected beak depth of the offspring produced by the mating of males with beak depth of 10 mm and female with beak depth of 8 mm. The effect on the beak size of offspring if the female’s beak was 10 mm and male’s 6mm.

Introduction: The variety of processes can lead to evolutionary change in an organism. The English naturalist, Charles Darwin, proposed the Darwinian theory of biological evolution by natural selection, which is accepted by most of the evolutionary biologists.

Explanation of Solution

Darwin’s finches are an example of evolution by natural selection. Darwin observed that the species of the finches were closely related and similar to each other except for their beaks. Darwin also observed that the difference between the beak sizes had evolved the adaption of various species to use different food resources.

Some species of finches feed on small tender seeds, but due to depletion of these seeds, the birds resort to larger and hard seeds. The large seeds were consumed by the birds with shorter, more profound, and more powerful beaks and survived better, whereas when the plants bear an abundance of small seeds, the birds with long and shallow beaks survived better. The depth of the beaks of parents is similar to the offspring. The mean of parents' beak depth will be 9mm, so the beak depth of the offspring will be approximately 9mm.

The depth of the beak does not depend on the sex of the parent. However, some points scatter close to the line of regression, which suggests that sex of the parent does not affect the beak depth of the offspring.