Evidence for Evolution

Changing Environments Select for Specific Genetic Phenotypes Before the Industrial Revolution the trunks of certain trees were a light color. The lighter peppered moths had an advantage over the darker moths. The lighter moths were more likely to survive and reproduce so there were more of them in the population. However, with the Industrial Revolution came pollution. The trees turned dark. Now the darker moths had the advantage. Adaptations are dependent upon the environment.

Fossils The Fossil record shows patterns of development It demonstrates that species have physically changed over long periods of time and diverged from common ancestors

Law of Superposition Fossils found in the lower rock strata are older than those found closer to the top.

2. Vestigial Structures These are structures still present in an existing species. However, they are reduced in size or function even to the point of serving no function whatsoever. (ex. wisdom teeth and appendix in humans, wings in flightless birds)

Vestigial Structures continued Vestigial structures support the theory of evolution by showing that species adapt to changing needs, leaving unnecessary organs behind.

3. Homologous Structures Homologous structures refer to anatomical similarities in different species, despite the function of the structure. Example: A bat’s wing and a human’s arm serve very different purposes, however, they share an almost identical bone structure.

Homologous Structures continued

Homologous Structures continued Homologous structures support the theory of evolution because they demonstrate that different species often share a common ancestor

4. Analogous Structures Analogous structures share similar functions but have very different anatomy. Example: A bat’s wing and a bird’s wing serve the same purpose: flight. However, the bone structure of a bat’s wing is more similar to a human arm than a bird’s wing.

Analogous Structures continued

Analogous Structures continued Analogous structures support the theory of evolution by demonstrating that very different species will form similar adaptations in the face of similar environmental pressures.

5. Embryology The earliest stages of embryonic development show astonishing similarities between species. This shows that the activated genes are very similar. This is corroborated by genetic sequencing.

Embryology continued Embryology supports the theory of evolution by showing that the genes activated earliest in an organism’s development have remarkably similar effects regardless of the species.

The tree of life has branched in countless different directions The tree of life has branched in countless different directions. However, we all came from the same roots.