biology 11
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Biology 11. Unit 1: Evolution Lesson 1: Why Evolution??. By the end of the lesson you should be able to: Explain why DNA is so important to the theory of evolution State the men of evolution and what they contributed to the developing theory - PowerPoint PPT PresentationTRANSCRIPT
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Unit 1: Evolution
Lesson 1: Why Evolution??
*Biology 11
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Objectives:
By the end of the lesson you should be able to:*Explain why DNA is so important to the theory of
evolution
* State the men of evolution and what they contributed to the developing theory
*Explain Darwin’s theories (Decent with Modification and Natural Selection) and his 2 problems
*Use these examples to explain evolution: Peppered Moth, Giraffe necks, Finch beaks
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DNA and Evolution
*Before we can truly understand evolution we need to understand DNA
*DNA = deoxyribonucleic acid
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Characteristics of DNA
1. Double helix
2. Sugar phosphate backbone
3. 4 nitrogenous bases (ATCG)
4. Complimentary base pairing
(A = T; C Ξ G)
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DNA and Evolution
*DNA is unique to each organism
*If DNA changes the organism changes
*Evolution is the change of populations of organisms over time
*THEREFORE the DNA must be changing over time if the organisms are changing!
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So What is Evolution All About?
*Evolution:
- the change through time
- all living and non-living things change over time
*We have lots of evidence that the earth is changing and has changed over time
This is a picture of what Alberta usedto look like. It was a Carboniferous Swamp that existed 300 mya…this is where our fossil fuels come from.
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Why Evolution?
*As the earth changes life must adapt or die
*Most life dies
*But some adapts and survives – this is evolution!!
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Evolution as a Theory
*Evolution is just a theory!
*It has a large body of evidence that is very widely accepted and has been scientifically tested for many years
*Its more than just a hunch or guess
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A Theory Emerges
*Charles Darwin is credited with formulating our modern theory
*He couldn’t have done so without all the scientists before him
*Lets look at who was working before Darwin
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Erasmus Darwin
*Believed that organisms evolved over time, including man, but didn’t know how
*Did not widely spread his ideas but profoundly influenced his grandson Charles
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Jean Baptiste Lamarck
*Proposed Inheritance of Acquired Characteristics
or “Theory of Use-Disuse”
*First person to propose a mechanism for evolution, although wrong, he really challenged peoples long held ideas
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Use-Disuse Theory
*If an organism uses a structure a lot and so do its ancestors, over time that structure develops better. Ex: Giraffes
*Why is this wrong?
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Charles Darwin
*As a young naturalist he sailed on a 5 year voyage around the globe on HMS Beagle
*During this trip, especially to the Galapagos Islands, he put all the evolution puzzle pieces together
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Darwin’s Ideas
*Darwin was puzzled by the diversity of life on the Galapagos.
*He knew these islands were young volcanic islands.
*He observed 13 varieties of finches, all clearly related, but different from the one variety found on the mainland
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Darwin’s 13 varieties of finches:
*note the variations in color and beak size
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Darwin’s Main Ideas*Darwin contributed two main ideas:
1. Evolution, which he called “Descent with Modification.”
2. The mechanism of evolution: Natural Selection
*Today we refer to Darwin’s theory as “Gradualism”
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Darwin’s Publication
*Although his voyage ended in 1836, he did not publish his theory until 1859
*He published “The Origin Of The Species”
*Although he was publicly ridiculed, the scientific community quickly became convinced
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Darwin’s Theory:Descent with Modification*In nature, more offspring are produced than can
possibly survive
*From this overabundance, there is a “struggle to survive” among the offspring
*In every population, there are variations in all traits
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Descent with Modification*Those offspring with variations that make them better
adapted to their environment are more likely to survive (Survival of the Fittest)
*Those offspring who survive will mate with others who possess the favorable trait and this trait will be passed on to future generations (Natural Selection)
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Two Problems with the Theory
1. Darwin couldn’t explain how variations could appear in a population.
- The answer was in Gregor Mendel’s work on pea genetics
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Problems with the Theory2. He could not show a
single example of evolution occurring today, ie evolution in progress.
- He missed a good example right under his nose: the Peppered Moths of the Manchester Forest.