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Chapter 21 Genes within populations. Question?. How did the diversity of life originate? Through the process of Evolution. Evolution. The processes that have transformed life on earth from its beginnings to today's diversity. Evolution is the most pervasive principle in biology.
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Question? • How did the diversity of life originate? • Through the process of Evolution.
Evolution • The processes that have transformed life on earth from its beginnings to today's diversity. • Evolution is the most pervasive principle in biology.
Hypothesis supported repeatedly by data. Makes testable predictions Layperson’s definition. Confused with hypothesis in Science. Theory vs theory
Examples of Theory • Cell Theory • Big Bang Theory • Atomic Theory • Theory of Gravity • Theory of Evolution
Evolution • Has itself "evolved" or changed over time. • Illustrates “Science as a Process”. • Students should be able to give the main points of several views.
Pre-Darwinian Views 1. Greeks 2. Fixed Species 3. Catastophism 4. Hutton and Lyell 5. Lamarck
Greek Philosophers 1. Plato - Organisms are already perfectly adapted to their environments. 2. Aristotle - Organisms arranged on a “scale of life” from simple to complex.
Result • No evolution. • Life is already perfect and doesn’t need to change. All the rungs on life's "ladder" are already occupied.
Fixed Species Concept • The creator had designed each and every species for a particular purpose.
Result • No evolution. • Created the viewpoint that all species could be identified and named (Taxonomy). A major factor in the Linnaeus classification system.
Georges Cuvier (1769-1832). Attempted to relate fossils to current life. Catastrophism
Theory • Fossils were the remains of species lost due to catastrophe. • No new species originated; species could only be lost over time. • Result - No evolution.
James Hutton • 1795 - Gradualism • Profound change is the cumulative product of slow, but continuous processes.
Result • Changes on the earth were gradual, not catastrophic.
1797 - 1875. Incorporated Hutton’s gradualism into a theory called Uniformitarianism. Charles Lyell
Uniformitarianism • Geological processes have operated at the same rate over the Earth’s history.
Result • The Earth must be VERY old. (much older than 6000 years of the fixed species concept). • Idea that slow and subtle processes can cause substantial change.
Published theory in 1809. Theory - Life changed from simple to complex over time. Jean Baptiste Lamarck
Lamark • Fossils were the remains of past life forms. • Evolution did occur.
Mechanisms 1. Use and Disuse - • Body parts used to survive become larger and stronger. • Body parts not used to survive deteriorate.
Mechanisms 2. Acquired Characteristics • Modifications acquired by use/disuse were passed on to offspring.
Problem • No knowledge of genetics. • Acquired traits are not transmitted offspring.
Lamarck’s Credits • Did suggest correctly the role of fossils in evolution. • Did suggest that adaptation to the environment is a primary product of evolution.
Father of the modern theory of evolution. Theory - Descent with Modification. Charles Darwin
Darwin's Background • Trained as a Naturalist (after trying religion and medicine).
Result • Darwin's training and travel opportunities allowed him to formulate and support his ideas on Natural Selection.
Paper on Natural Selection identical to Darwin's ideas. Alfred Wallace - 1858
Result - July 1, 1858 • Dual presentation of the Wallace-Darwin ideas to the Linnaean Society of London.
Publication of "The Origin of Species” Darwin - 1859
Comment • Darwin best remembered for the theory because of his overwhelming evidence and because he published.
Darwinian View • History of life is like a tree with branches over time from a common source. • Current diversity of life is caused by the forks from common ancestors.
“The Origin of Species” • Documented the occurrence of evolution. • Suggested that the mechanism for evolution was Natural Selection.
Fact 1 - All species reproduce themselves exponentially. The Facts:
Fact 2 - Most populations are normally stable in size. Fact 3 - Natural Resources are limited (finite).
Inference 1 • The large number of offspring must compete for the finite resources. • Result - Most offspring die.
Thomas Malthus • Essay on human population growth in 1798. • Disease, famine, homelessness, and war are inescapable because human populations grow faster than food supplies. • Darwin read Malthus.
More Facts Fact 4 - No two individuals in a population are exactly alike. Fact 5 - Variation is inheritable.
Inference 2 • Those individuals whose inherited characteristics fit them best to their environment survive and reproduce.
Inference 3 • Offspring inherit the favorable characteristics. Populations shift over time as the favorable characteristics accumulate.
Nature • Determines which characteristics are favorable. • Determines who survives. • Result - “Natural Selection”
Artificial Selection • When man determines the characteristics that survive and reproduce. • Result - the various breeds of animals and plants we’ve developed.
Original Cultivars Ex - Mustard Plant
Evolution Success Measured By • Survival • Reproduction • Whoever lives long enough and has kids is the “winner” in evolution.