The Theory of Evolution

Charles Darwin  19 th century English naturalist  developed a theory on how evolution works  studied on the Galapagos Islands because each island had different environments  wrote On the Origin of Species

Darwin’s Theory  Species evolve from a common ancestor  Variation – slight difference in an inherited trait of individual members of a species  occurs as a result of mutations during sexual reproduction

Natural Selection "Survival of the Fittest”  organisms with variations that help them survive, live longer and are therefore able to reproduce to pass on those variations  ex. tortoises with longer necks will survive longer than tortoises with short necks if the food sources are up high

Adaptations  an inherited trait that increases an organism’s chance of surviving and reproducing in its environment

3 Types of Adaptations  Structural – involve physical characteristics  ex. coloration, shape  Behavioral – involves the way an organism acts  ex. hunting at night, moving in herds  Functional – involve internal body systems  ex. hibernation, temperature regulation

Environmental Interactions Camouflage  an adaptation that enables a species to blend in with its environment Mimicry  the resemblance of one species to another species

Evidence of Evolution

Comparative Anatomy  the study of similarities and differences among structures of living species  Homologous Structures – body parts of organisms that are similar in structure, but different in function

 Analogous Structures - body parts that perform a similar function, but differ in structure  ex. bird wings and insect wings

Vestigial Structures  body parts that have lost their original function through evolution  shows that the structures served a purpose at one point, but now are no longer needed  ex. cormorant wings, whale pelvic bones

Developmental Biology  Embryology – study of embryos from fertilization to birth

Molecular Biology  Scientists can use DNA to show how closely related organisms are  Divergence – the point at which an organism breaks away from its common ancestor