8.2-Sources of Evidence for Evolution SBI3U1

Evidence for Evolution The theory of evolution by natural selection was proven by the following methods: Fossil Record Biogeography Anatomy Embryology DNA

1) Fossil Record Fossils are found within the layers of sedimentary rock. Specific fossils are found in specific strata (rock layers). Fossil groups are unique to each stratum. paleontologists use this to determine dates

A geological time scale

Youngest Fossils (closest to the surface) Oldest Fossils

Evidence from the 1)Fossil Record Evidence from Fossil Record: Fossils within the younger layers are most similar to species alive today. Fossils appear in chronological order within the sedimentary layers. Not all organisms appear in the fossil record at the same time.

Paleontologists have used fossils to trace the evolution of the modern camel. The Paleocene, Eocene,Oligocene, and Miocene epochs are subdivisions of the Cenozoic era.

Evidence from Transitional Fossils Scientists are always looking for transitional fossils that show an intermediary link between past and present groups of organisms. Vestigial structures are reduced versions of what were once functional structures in an ancestral species

2) Biogeography Biogeography=Study of geographical distribution of species 1)Geographically close environments are more likely to be populated by related species. 2)Animals found on islands often closely resemble animals on the nearest continent. 3)Fossils of the same species can be found on the coastlines of neighbouring continents

3) Anatomy Notice that these vertibrates have the same basic arrangement of bones but the bones have different uses.

Which limb does not belong? Human

Which limb does not belong?

Evidence from Anatomy Homologous structures = structures that have similar structural elements and origin but may have a different function. They originate from a common ancestor. Ie. Limbs, hair Analogous structures= structures that do not have a common evolutionary origin but perform similar functions. These provide evidence for adaptation to suit the environment. Ie. the fins of a porpoise and a fish.

Homologous Structures All of these organisms have a similar bone structure. They were inherited from a common ancestor

Analogous Structures Example: Insects, Birds, and Bats all have wings used for flight (function) but insects do not come from a common ancestor because there are no bones. *Note: Your textbook describes bird and bat wings as analogous, this is NOT true.

Analogous Structures Example: Penguins and fish both has fins for swimming. The fin evolved as a structural adaptation, not from a common ancestor.

Test your Understanding.. Homology or Analogy? In this module, you learned that homologies are traits that different lineages inherited from their common ancestor. Homologies are evidence that different species shared a common ancestor. Analogies, on the other hand, are similar traits that were not inherited from a common ancestor but that evolved separately. Analogies often exist because two different lineages became adapted for similar lifestyles. Sugar gliders and flying squirrels look amazingly similar. They are both furry animals of about the same size, with big eyes and a white belly. And they both glide from treetops using a thin piece of skin that is stretched between their legs. This piece of skin helps keep them stable while gliding. However, these animals also have some key differences: Sugar gliders live in Australia, and flying squirrels live in North America. Sugar gliders have a pouch (like a kangaroo does), which provides shelter and safety for their tiny babies — at birth, a baby sugar glider is smaller than a peanut! Flying squirrels, on the other hand, have much larger babies and no pouch. By studying their genes and other traits, biologists have figured out that sugar gliders and flying squirrels are probably not very closely related. Sugar gliders are marsupial mammals and flying squirrels are placental mammals.

Answer: Analogous Structures Both types of squirrels have evolved from different lineages

Homology vs. Analogy Homology Analogy Evolved from separate lineages Elvis Fans Sisters Have a common ancestor (mother) In everyday life, people look like one another for different reasons. Two sisters, for example, might look alike because they both inherited brown eyes and black hair from their father. On the other hand, two people attending an Elvis impersonators' convention may look alike because they are both wearing rhinestone studded suits and long sideburns. The similarity between the sisters is inherited, but the similarity between the Elvis impersonators is not. Homology Analogy

4) Embryology Embryology: the study of pre-birth stages of an organism’s development -used to determine evolutionary relationships between animals: Similarities in the embryos of fish, birds, and mammals provide evidence of evolution of species from a common ancestor.

5) DNA By comparing organisms’ genetic sequences, scientists can determine their level of similarity. Two organisms with similar patterns of DNA, suggests that they inherited this information from a common ancestor.

Homework Read and make notes 8.2 Complete pg. 340 Q# 1- 3, 8-12