Evidence of Evolution

The Fossil Record Fossils are the remains or traces of an organism that died long ago. Fossils show that organisms appeared on Earth at different times and geological places. Fossils are the only evidence of organisms that are now extinct. Extinct – whole species that are no longer living.

The Age of Fossils Nicolaus Steno a Danish scientist proposed the principle of superposition in 1669. Superposition is a principle that states that if a rock strata at a specified location is has not been disturbed, the lowest strata was formed before the strata's above.

The principle of superposition gave rise the geologic time scale. Geologic time scale is a timeline scientist use to data fossils found in strata.

Dating Fossils 2 types of fossil dating Relative age – the age of the fossil is determined by comparing fossil to each other and referring the fossils to the geologic time scale. Absolute age – some rocks are radioactive and by using the known information of how long it takes for radioactive material to decay scientist can determine how old a rock strata is and accurately data fossils

Using Fossils scientists can make inferences about past organisms. 1st scientists can infer that different fossils lived at different times. 2nd scientists can infer that today’s organisms are different from those of the past. 3rd scientists can infer that fossil found in strata close to each other are more alike than that of those found far apart. 4th scientist can identify where and when different organisms existed

Transitional Species Using fossil records we can see how organisms have changed over time. Transitional species are organisms that have features that are intermediates between the ancestors and the later descendants.

Anatomy and Embryology Anatomy is the study of the body structures of organisms Embryology is the study of how organisms develop. Using these features scientists can make hypothesis about organisms past.

Anatomic structures Homologous structures are structures that occur in different species and that originated by heredity from a structure in the most recent common ancestor of those species.

Analogous structures are anatomical structures that have closely related functions but do not come from a common ancestral structure.

Embryonic Development Scientists have found similarities in the embryonic development for deferent species that suggests those species share a common ancestor.

Biological Molecules Scientists can compare the DNA, RNA, proteins, and other biological molecules from many different species to determine if the organisms are related.

Developing Theory The Theory of Evolution is still changing due to more information found in the fossil record. With the information from the fossil record scientists have developed phylogenies to group species.

Phylogenies show the relationships between species by grouping them with common ancestors.

Each branch represents a separate population or lineage. More closely related groups appear closer than less related groups.