Evidence for Evolution

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This presentation gives the most common evidences used to support the theory of evolution.

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Evidence of Evolution:

Evidence of Evolution Points of Proof

Objectives:

Objectives Describe how the fossil record supports evolution. Summarize how biological molecules such as proteins and DNA are used as evidence of evolution. Infer how comparing the anatomy and development of living species provides evidence of evolution.

The Fossil Record:

The Fossil Record In the same way a series of maps made over time show the growth of a city, the fossil record shows evidence of change within a species over many generations. Fossils are a mineralized imprint of a past life-form. They provide an actual albeit limited record of life from Earth’s past. Change over time can be seen in fossils.

The Premises of Evolution:

The Premises of Evolution Evolution theory depends the following three premises: The Earth is over 4 billion years old (Old Earth Theory) Organisms have inhabited the Earth for most of its existence. All organisms living today share a common ancestry with earlier, simpler life-forms.

Formation of Fossils:

Formation of Fossils The fossil record, as an evidence of evolution, is incomplete. Most species lived in an environment where fossils do not form. Fossils form best in areas where the fallen specimen can be rapidly buried in layers of light sediment deposited by water, wind, or volcanic eruption. The environment most likely to produce fossils would be wet lowlands or swamps, slow moving streams, or areas near volcanoes that spew out volcanic ash. The chances of an organism that spends it life in an upland forest, for example, going down into a swamp and dropping dead are very small.

The Fossil Record:

The Fossil Record Most often, dead animals are eaten and their remains scattered over a large area before they can be buried in sediment. Fossil formation is a rare process.

Anatomy and Development:

Anatomy and Development Comparison of the anatomy or internal structures of different species often reveal basic similarities in body structure, even though the structures may differ in function. Sometimes bones or organs are present in an individual but are reduced in size and either have no use or very limited use. These organs or bones are considered vestigial.

Forelimb Development:

Forelimb Development The fore limbs of different animals show similar bone structure and design. Though the bones are differently shaped and sized, the arrangement is similar in all species, one upper limb bone, paired lower limb bones, and many smaller bones connected by sliding joints forming the hand or paw and fingers. This type of similar development is called homologous structures. The design is the same even if the function is slightly different.

Biological Molecules:

Biological Molecules One idea used to support evolution involves the analysis of proteins and amino acids in the tissues of different species in order to tell how closely they are related. The theory proposes that the closer two species are to a common ancestor, the more similar proteins they will share. For example, humans and gorillas share many common proteins. They are considered closely related. However, gorillas and frogs share few common proteins. They are not closely related.

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