Darwin & natural selection

Darwin & natural selection

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  Charles Darwin & NaturalSelection
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  Darwin’s Theory  EVOLUTION– all changes that have transformed life over immense time.  “Evolution is the biological history of life on Earth”  Before Darwin people thought: 1. species are fixed -they do not change 2. Earth is less than 10,000 yrs old https://flic.kr/p/9D76x3 Rights Reserved under CC BY 2.0
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  The Changing ofIdeas  In the mid 1700’s, his study of fossils caused Georges Buffon to suggest that the Earth might be much older  He also noticed that some fossils and some living organisms were similar, but not exactly alike
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   LAMARCK  Proposedthat life evolves/changes  It Adapts  Ex: hind legs of a kangaroo  How did massive hind legs of a kangaroo allow them to adapt to the environment? Macropus giganteus https://commons.wikimedia.org/wiki/File:Macropus_major_hind _legs.png Rights Reserved under CC BY-SA 4.0
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  Charles Darwin Travels toGalapagos Islands
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  The Infamous Voyageof Darwin  Charles Darwin voyaged on the H.M.S. Beagle to the Galapagos Islands – saw lots of animals, read lots of books, did lots of thinking – and came up with the following:
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  Darwin  Observed thatthe Galapagos Islands had many unique organisms, similar to, but different than those on the mainland  Also noticed that each island had some organisms that were not found on any other islands in the chain  Inferred that mainland species had changed after colonizing the islands, and adapted to their new environments
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  Mr. Darwin, yourthoughts please?  Organisms Change Over Time  How? Natural Selection!  All organisms can produce more offspring than can survive  There are variations between the individuals in a population  Limited resources = struggle to survive  Individuals with the traits that make them the most “fit” have better chance of surviving and passing their traits to their children
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   Why isvariation important?  Variation allows natural selection to happen  How?  Survival of the fittest- The best adaptation (variation) will survive and reproduce  Can you think of any other examples of survival of the fittest? What variation allowed for survival? Variation Exists within a Species
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  The Backbone ofEvolution  Scientists study the fossil record to compare extinct organisms to modern organisms  The fossil record indicates:  the order in which species emerged  How do we get fossils?  in wet, environments where they can be quickly covered by sediment  How old are fossils?  Relative dating -top layer must be younger than bottom layer  Radiometric (absolute) dating -use radioactive isotopes- decay (half life)
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  Analyzing the Presentto Understand the Past- Evolutionary Support Comparative Anatomy: Compare body structures of different species Homologous structures: similar to due to common ancestry ex: human arm and whale flipper https://www.flickr.com/photos/bibliodyssey/6245974006/galleries/
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  Homologous Body Structures ‘HomologyVertebrates Rights Reserved under CC BY-SA 4.0
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  Vestigial Structures: Remnants ofStructures that may have been useful in the past, but have little or no importance now. Ex. Appendix Tail Bone
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  Biochemistry: Similarities in DNAand protein sequences https://commons.wikimedia.org/wiki/File:Schematic_relations hip_between_biochemistry,_genetics_and_molecular_biology .svg Rights Reserved under CC BY-SA 3.0
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  Natural Selection  Explainsresistance of insect populations to pesticides or bacteria to antibiotics  Spray insecticide  Those that aren’t resistant - die  Those that are resistant - live and reproduce  The next generation contains more resistant individuals - the population is changing  Adaptation Is a variation, not a change! ‘Colorado Potato Beetle Public Domain
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   Overuse ofantibiotics has lead to strains of bacteria that are resistant to them.  The bacteria adapted and now have a resistant gene. Antibiotic Resistance
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  Genetic Drift  Movementof genes in or out of a population  Greatly affects small populations Geographic Isolation  A barrier separates one population into two  They evolve different characteristics  They become different species- they coevolve