Evidence of Evolution Grade 8 Science

Theory of Evolution Review Organisms develop adaptations to their environment in order to survive. The better suited they are to the environment, the longer they will survive (“Survival of the Fittest”). Those adaptations or traits are genetically passed down to their offspring. So, why do these traits vary or differ among members of the same species?

Genetic Variation The characteristics that make members of the same species different from one another. Variation: different forms of a trait.

How Do We Know Evolution Has Occurred? Supported by fossil evidence Fossils: Preserved remains or traces of living things.

Fossils

How Do We Know Evolution Has Occurred? Fossils Provide a record of life on earth Comparison of organisms living today and organisms in the fossil record enable the reconstruction of evolutionary history.

Evidence of Evolution Embryology Developing embryos of different animals have similar characteristics. These similarities hint at the genes inherited by common ancestors.

Evidence of Evolution Comparative Anatomy - Analysis of body structures of two or more species that provides insight into the genetic/biological similarities and differences across species.

Evidence of Evolution May or may not have same function Homologous Structures - Similar body structures or systems with the same evolutionary origin. May or may not have same function The structure gradually changes in animals to better suit their environment.

Homologous Structures Example: The humerus bone in these animals are the same, but have changed over time to better suit their environment (arms, wings, or fins).

Evidence of Evolution Have no apparent or lesser function Vestigial Structures Have no apparent or lesser function Suggest the loss of the original function through evolution

Vestigial Structures Example: The pelvis (hip) and femur (leg) bones appear in organisms of many species, despite the function of these bones. The salamander still uses these bones today, but does the whale and snake? Why would the whale and snake still have these bones but not use them?