Unit 1: Evolution

Lesson 1: Why Evolution??

*Biology 11

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

DNA and Evolution

*Before we can truly understand evolution we need to understand DNA

*DNA = deoxyribonucleic acid

Characteristics of DNA

1. Double helix

2. Sugar phosphate backbone

3. 4 nitrogenous bases (ATCG)

4. Complimentary base pairing

(A = T; C Ξ G)

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!

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.

Why Evolution?

*As the earth changes life must adapt or die

*Most life dies

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

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

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

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

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?

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’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”

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

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

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)

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

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.