The main lines of evidence of evolution are: Fossil Record Homologous Structures Vestigial Structures Embryology Similarities in DNA

Fossil Record It is possible to find out how a particular group of organisms evolved by arranging its fossil records in a chronological sequence Provides evidence of changes in species over time

Formation of Fossils Fossils form when an organism dies and becomes buried in sediment With a lack of oxygen, the organism does not decay and the minerals in the sediment replace the organic materials of the organism This turns the dead organism into solid rock Also why fossils are almost always only found in layers of sedimentary rock

Types of Fossils Molds and Casts Most common Molds leave hollow impression Casts are a solid copy of the organism

Types of Fossils Petrified Fossils Minerals replace part or all of the organism Ex- petrified wood

Types of Fossils Trace Fossils Provide evidence of a once living organism Ex- footprints, burrows, dun

Types of Fossils Preserved Remains A process that preserves an organisms with little of no change Ex- amber, ice, tar

Homologous Structures Similar structures in different organisms that develop from the same embryonic tissue Provides evidence of a common ancestor

Vestigial Organs A structure in an organism that has lost all or most of its original function over the course of evolution. Provides evidence of changes in a species over time

Comparative Embryology The study of similarities and differences in the early development of plants and animals Similarities (like tails and gill slits of vertebrates) provides evidence of a common ancestor

Similarities in Early Development

Similarities in DNA Species that are closely related have very similar sequences in DNA Provides evidence of a common ancestor

So........ we have the evidence, we know species adapt, we know nature selects those that are most fit to survive, but how does a species change? One mutation at a time!

A mutation is a change in the DNA base sequence of a gene.

Changes in DNA may change an organism’s physical appearance.

Mutations Harmful mutations hurt the success of the individual. Provide an example of a harmful mutation. Beneficial mutations help the success of the individual Provide an example of a beneficial mutation. Neutral mutations do not help or harm the success of the individual. Provide an example of a neutral mutation.

Speed of Evolution Gradualism- evolution happens gradually over many generations and long periods of time What types of events or circumstances do you think would make gradual changes in a species?

Speed of Evolution Punctuated Equilibrium- evolution that happens quickly over just a few generations What types of events or circumstances do you think would make quick changes in a species?

The End