Formation of Fossils

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I. The Edvidence of Fossils

A. (28-1) The Formation of Fossils

1. Fossil: The actual remains or any trace of an organism that lived at some time in the past.
2. Petrifaction: The process by which the body of a dead organism is slowly replaced by dissolved minerals.
3. Mold: A rock as a hollow form; Cast: A copy of the external form of the original organism.
4. Imprint: A type of fossil formed when an impression made in mud by a living thing is preserved when the mud is transformed into rock.

B. (28-2) Sedimentary rocks:

1. Sedimentary Rock: A type of rock formed from layers of particles that is settled to the bottom of a body of water, often containing fossils. 2. Water flowing into these bodys of water carry fine particles of rock called sediments.
3. The size and mineral composition of sediments being deposited by the rivers will usually change from time to time. Therefore, the sedimentary rock acquires a layered structure.
4. Geologists have concluded that the crust of the earth is constantly changing and shifting.

C. (28-3) Hormones

1. Relative Dating: Any method of determining the order in which events occured.
2. Correlation: The process of matching by which geologists determine the relative ages of rock layers
3. A study of fossils from many regions have shown that certain types of organisms seem to appeared, flourished for a time over wide regions of the earth, and then disappeared.
4. Transitional forms: Missing links

D. (28-4) Absolute Dating
1. Relative dating allows us to say that one type of organism lived earlier than another, but it does not tell us how much earlier.
2. Absolute dating: Any method that does enable us to find out how long ago an event occured.
3. Thecrate at which a radioactive element decays is fixed and unchangeable. 4. Radioactive dating methods cannot be applied to sedimentary rocks. E. (28-5) The Geologic Time Scale

1. Through a combination of absolute and relative dating of rocks, geologists have constructed a timetable of earth’s history, which is known as the geologic time scale.
2. Each era is subdivided into periods and eboch.
3. Radioactivty: The property of emitting radiation.
4. Igneus Rocks: rocks that formed when molten material in the crust cooled and harden.

II. Other Evidence of Evolution

A. (28-6) Evidence from Comparative Anatomy

1. Comparative Anatomy: Is the study of structural similarities and differences among living things.
2. Homologous structures: Parts of different organisms that have similar structures and similar embryonic development, but different forms and functions. 3. Analogus structures: Structures that have similar external forms and functions but quite different internal structure.
4. Vestigal Structures: A nonfunctional structure in an organism that is a

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