Chapter 15, Problem 18A

Summary Introduction

To describe:

How cytochrome C provides evidence of evolution

Introduction: Darwin got the idea that the principle of Malthus could be applied to natural world. He gave a new theory of natural selection that could explain evolution of species. The theory of evolution states that all organisms on earth have a common ancestor. There are many evolutionary evidences that suggest this.

Answer to Problem 18A

Cytochrome c is a highly conserved protein that has changed very little over time despite variations in amino acid sequences of cytochrome c in humans and other organisms. So it provides evidence that organisms with common ancestry have common metabolic systems.

Explanation of Solution

Comparative biochemistry provides evidence for common ancestry. Data shows that there are many complex molecules that organisms share. Cytochrome c is a highly conserved enzyme that is needed for respiration in animals. It is found that the amino acid sequences in cytochrome c in humans and other animals have undergone slight variations but the molecule has changed very little over time.

Evolutionary theory predicts that molecules in species with a common ancestor should share certain amino acid sequences. The more closely related the species are, the greater will be the number of sequences they share. Cytochrome c of pig and monkey share more amino acid sequences with humans than cytochrome c in bird shares with humans.