1 the theory of natural selection biology i. 2 i. early biology scientists knew that organisms had...
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The Theory of Natural Selection
Biology I
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I. Early Biology
• Scientists knew that organisms had changed
• Fossil evidence
• Age of the Earth
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Lamarck
• Changes from simple to complex
• Organisms want to adapt or change
• Acquired characteristics were inherited (passed on)
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Lamarck
• Later disproved
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II. Darwin• At 21, took a job as
a naturalist on the HMS Beagle
• Collected specimens, took notes of different organisms
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His voyage:
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II. Darwin
• Sailed to Galapagos Islands
• All new species, but similar to those found elsewhere
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• Finches most famous• Had slightly different beaks from island to island• Differed by their diet
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II. Darwin
• Darwin 22 years developing theory of natural selection
• Pressured into publishing by Wallace
• Published On the Origin of Species by Natural Selection
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III. Natural Selection 4 Requirements
•1. Variation exist
• 2. Differential Reproduction
• 3. Heredity Best suited survive and reproduce
• 4. Lots of Time
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1. Variation
• Variations exist– Color, size, speed, etc.
• Variations are genetically linked
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2. Differential Reproduction
• Organisms produce more offspring than can survive– creates competition and
Survival of the Fittest = Only the best are going to survive
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Heredity
• Beneficial variations survive, pass traits to offspring
• Passed through DNA
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Natural Selection
• Over time variations become more frequent in population
• Results in population being different than ancestors
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EvolutionEvolution is the change in a population over time
Natural Selection - Remember the Giraffe?How did it get the long neck?
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Evidence of Change
• Fossil Record• Anatomy & Physiology• Embryology• Biochemistry
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Fossils
• Remains or traces of living organisms
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Physiology Mimicry-An adaptation
• Enables one species to resemble another species.
• Ex.-harmless species looks like a harmful one, good tasting vs. bad tasting.
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Camouflage-An adaptation
• A species blends in with its environment to avoid predators.
• Ex.- peppered moth,
leaf frog
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Anatomy- Homologous Structures
• Common evolutionary origin. Similar in arrangement or function or both.
• Example: forelimbs of a whale, a crocodile and a bird wing.
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Anatomy- Analogous Structures
• No common evolutionary origin, but similar in function.
• Wings of a bat and wings of a butterfly.
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Anatomy- Vestigial Structures
• No function now but was probably useful to an ancestor.
• Ex. A whale has leg bones, a snake has leg bones
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Embryology
• Earliest stage of growth and development • Embryos of a fish, a chicken, a pig, a cow,
a rabbit, and a human are almost identical.• They all have gill slits and a tail.
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Biochemistry
• Comparisons of DNA and RNA • Now monera (prokaryotes) is divided into
two separate kingdoms based on their biochemistry.
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V. Mechanisms of Evolution
• Genetic Drift• Gene Flow • Artificial Selection • Natural Selection
Sexual Selection
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Genetic Drift
• Change in allele frequency by CHANCE
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GENE FLOW
• Bottleneck effect
• Founders effect
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Gene Flow
• Change in allele frequency as a result of MIGRATION
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Sources of Variation• GENE FLOW moves genes among
populations• SEXUAL REPRODUCTION
introduces new gene combinations • Random MUTATIONS in DNA
lead to the formation of new alleles (sound familiar?)
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Mutations
• Can be beneficial, neutral, or harmful for the organism
• Only mutations in gametes are inherited by offspring
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Bell:
• What is the difference between Analagous structures, Homologous Structures, and Vestigial Structures?
• What are the 4 requirements of Natural Selection?
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AGENDA•Intro to Classification•Natural Selection Today
•Antibiotics