Download 10.2 evidence for evolution

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Notes Outline: The Evidence for Evolution (10.2)
“MUCH OF WHAT YOU HAVE READ SO FAR IN THIS BOOK WAS UNKNOWN TO DARWIN WHEN HE WROTE THE
ORIGIN OF SPECIES. THE NUCLEIC ACIDS DNA AND RNA HAD NOT BEEN DISCOVERED. THE STRUCTURE OF
PROTEINS WAS UNKNOWN. MENDEL’S GENETIC EXPERIMENTS WERE UNPUBLISHED. THESE AND OTHER
DISCOVERIES HAVE SINCE CONTRIBUTED ADDITIONAL EVIDENCE FOR EVOLUTION.”
I.
Understanding the Fossil Record
A. Introduction
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Since Darwin’s death, a great deal of new evidence accumulated supporting the theory of Evolution.
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B. Fossils Are Any Traces of Dead Organisms
II.
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Fossils are not only shells or old bones. Actually they are any traces of old organisms.
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For fossils to form, very special conditions are necessary
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How Fossils Are Dated
A. Introduction
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(1940s) Scientists determine the age fossils by measuring the amt. of radioactive decay
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A radioactive atom contains an unstable combination of protons and neutrons, which will later become a more stable atom of
another element.
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Half-life: Describes how long it takes for ½ of the radioactive atoms in a sample to decay
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Because the rate of decay of radioactive element is constant, scientists can use the amount of radioactive element remaining in a
rock or fossil to determine its age.
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Radioactive Dating: Using the amt. of radioactive element in a fossil to determine its age
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Using radioactive dating, scientists have determined that the earth is about 4.5 billion years old.
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B. Transitional Forms Link New Species to Old
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B/c new species form from existing species, Darwin predicted that transitional forms, intermediate stages b/w older and newer
species, would be found in the fossil record.
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There are now many good examples of evolutionary transitions.
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Ex. The evolution of the modern horse
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Name_____________________________ Class #_____ Period_____ Date___________
III.
Comparing Organisms
A. Introduction
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Comparing the way organisms are put together provides important evidence for evolution.
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Homologous Structures: _____________________________________________________________
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B. Vestigial Structures are Clues to Evolutionary Origins
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Structures without a function are found in living things
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Ex. Pelvis of a whale
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Vestigial Structures: ________________________________________________________________
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C. Developmental Patterns Show Evolutionary Relationships
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The similarity of early developmental forms suggests that the process of development has evolved.
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New instructions on how to grow have been added to old instructions inherited from ancestors.
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D. DNA and Proteins Contain Evidence for Evolution
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Although complete fossil histories for living organisms are rare, an organism’s history is written in the sequence of nucleotides
making up its DNA.
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If species have changed over time, their genes also should have changed.
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Evolution predicts that genes will accumulate more alterations in their nucleotide sequences over time.
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Closely related species should show more similarities in nucleotide sequences than distantly species.
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Closely related species will show more similarities in the amino acid sequences in their proteins.
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Amino acid sequence in a protein reflects the nucleotide sequence of the gene coding for that protein.
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Ex. Cytochrome C b/w chimp and human are exactly identical
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In most cases, the evolutionary relationships indicated by DNA or protein sequences confirm those suggested by comparative
anatomy and by developmental patterns.
Sections Completed _______________ Questions Answered ____________ Final Grade ___________