Theory of Evolution by Natural Selection Ch. 6 Sect 2

Charles Darwin Was an English Naturalist who developed a theory of how evolution works. Naturalist is a person who studies plants and animals by observing them. Theory is an explanation of the natural world that is well supported by evidence. Darwin studied the animals on Galapagos Islands, especially the tortoises, mockingbirds and finches (differences).

Darwin’s Theory He realized that there was a relationship between the species and the available food on each island. Ex. Long neck tortoises – tall cacti He believed that all tortoise species had a common ancestor. Their physical characteristics changed to match the island’s food source.

Variations Darwin knew that members of a species exhibit variations. Variations – is a slight difference in an inherited trait of individual members. Variations occur in the offspring of sexual reproduction. Variations are caused by random mutation.

Natural Selection Is the process by which populations of organisms with variations that help them survive in their environments live longer, compete better, and reproduce more than those that do not have the variations. Explains how populations change as their environments change.

Adaptation Is an inherited trait that increases an organism’s chance of surviving and reproducing in its environment. Adaptation occur through the process of natural selection. Accumulation of variations can lead to adaptation.

Types of Adaptations 3 categories: structural, behavioral, and functional. Structural adaptations involve color, shape, and other physical characteristics. Behavioral adaptations involve the way an organism behaves. Functional adaptations involve internal body systems that affect biochemistry.

Environmental Interactions Species must adapt to an environment’s biotic and abiotic factors. Biotic and abiotic factors are constantly changing. Camouflage allows an organism to blend in with its environment. Mimicry allows an organism to resemble another organism. Fossil record contains many fossils of species unable to adapt to change.

Artificial Selection Selective Breeding is the breeding of organisms for desired characteristics. Changes caused by selective breeding were much like the changes caused by natural selection, only instead of nature selecting variations, humans selected them.