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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

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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

  • 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


Before we can truly understand evolution we need to understand DNA

DNA = deoxyribonucleic acid

DNA and Evolution

Double helix

Sugar phosphate backbone

4 nitrogenous bases (ATCG)

Complimentary base pairing

(A = T; C Ξ G)

Characteristics of DNA

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!

DNA and Evolution

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 used

to look like. It was a Carboniferous Swamp that existed 300 mya…this is where our fossil fuels come from.

Why Evolution?

  • As the earth changes life must adapt or die

  • Most life dies

  • But some adapts and survives – this is evolution!!

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

Evolution as a Theory

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

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

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

Jean Baptiste Lamarck

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?

Use-Disuse Theory

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

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

Darwin’s 13 varieties of finches:

  • note the variations in color and beak size

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”

Darwin’s Main Ideas

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

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

Darwin’s Theory: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)

Descent with Modification

Two Problems with the Theory

  • Darwin couldn’t explain how variations could appear in a population.

    - The answer was in Gregor Mendel’s work on pea genetics

Problems with the Theory

2. 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.

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