Evolution Evidence and Patterns

1. Fossils remains or traces of organisms that lived in the past

Relative Dating only describes if a fossil is older or younger than another fossil

*Fossils found in lower layers of sedimentary rock are older than fossils found in layers of rock above them.

Younger Older

Absolute Dating gives a specific age for a fossil

ex: This fossil is 84 million years old.

1 year 3 years

Uses the half life of certain atoms (carbon and uranium) that made up the organism to determine its age.

2. Anatomy structure of an organism* Homologous structures have the same structure & origin but different function (job)ex: forelimbs of humans, bats, whale, etc

3. Biochemistry study of chemicals and molecules that make up living organisms

ex: DNA and proteins *Scientists believe that the more similarities organisms have, the more closely related they are.

Over 98% of the DNA in chimpanzees and humans is the same.

4. Embryology study of embryos

Scientists believe that the longer the embryos look alike during development, the more closely related they are.

Coevolution when two organisms evolve so that they are completely dependent on each other.

Angiosperm(plant with Hummingbird flowers)

The shape of the flower and the shape of the beak of the bird demonstrate coevolution.

Patterns in Evolution

Convergent Evolution when two very different organisms evolve and become more similar as a result of their environment.

Speciation development of a new species

Organisms that can make and produce fertile offspring

Lions and tigers are different species because although they can mate, their offspring are STERILE.

Divergent Evolution when a single species or group of related species evolve & become more different

Adaptive Radiation when one species evolves into MANY different species

Answer the following questions on your own paper to turn in. :) 

1. Explain why the peppered moths in London changed from being primarily light colored to primarily dark colored. What happened to the moths' genes?

2. How are beneficial traits 'selected for' and undesirable traits 'selected against' in natural selection?

3. The alleles found in a population are changed through natural selection. Describe how the changed alleles affects the phenotypes found in that population.

4. Describe the difference directional and stabilizing selection. Give examples of each. 

5. Why might directional selection be beneficial in some circumstances while stabilizing selection may be beneficial in others?