Three-spined stickleback fish live in lakes formed when the last ice age ended 10,000 to 15,000 years ago. In lakes where the sticklebacks are prey for larger fish, they develop 35 bony plates along their body as armor. In contrast, sticklebacks in lakes where there are no predators develop only a few or no bony plates. Loss-of-function mutations in the coding region of the homologous gene in humans result in loss of hair, teeth, and sweat glands, as in the toothless men of Sind (India). What does this suggest about hair, teeth, and sweat glands in humans?

Key Concepts

Natural Selection

Natural selection is a fundamental mechanism of evolution where organisms better adapted to their environment tend to survive and reproduce more than those less adapted. In the case of the three-spined stickleback fish, the presence of predators drives the development of bony plates as a protective adaptation, illustrating how environmental pressures can shape physical traits over generations.

Genetic Mutations

Genetic mutations are changes in the DNA sequence that can lead to variations in traits. Loss-of-function mutations, like those affecting the homologous gene in humans, can result in the absence of certain features, such as hair, teeth, and sweat glands. Understanding these mutations helps explain how specific traits can be lost or altered in response to evolutionary pressures.

Homologous Genes

Homologous genes are genes that share a common ancestry and often retain similar functions across different species. The reference to a homologous gene in humans suggests that the genetic basis for traits like hair and teeth is conserved across species, indicating that evolutionary changes in these traits can provide insights into human development and adaptation.