1. Unit 1: Evolution Lesson 1: Why Evolution??
Biology 11H
Unit 1: Evolution
Lesson 1: Why Evolution??

2. 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
Objectives:

3. Before we can truly understand evolution we need to understand DNA
DNA = deoxyribonucleic acid
DNA and Evolution

4. Characteristics of DNA
Double helix
Sugar phosphate backbone
4 nitrogenous bases (ATCG)
Complimentary base pairing
(A = T; C Ξ G)
Characteristics of DNA

5. 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!
DNA and Evolution

6. So What is Evolution All About?
- 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.

7. Why Evolution? As the earth changes life must adapt or die
Most life dies
But some adapts and survives – this is evolution!!

8. 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
Evolution as a Theory

9. 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

10. 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

11. 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……the new discovery of “jumping genes” provides evidence to support Lamarck’s theory!

12. 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 does this sound “wrong”?

13. 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
Charles Darwin

14. 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

15. Darwin’s 13 varieties of finches:
note the variations in color and beak size

16. Alfred Russell Wallace
Sailed to South America and formulated the same theory as Darwin
Except his boat sank on the return trip with all his evidence 
Presented his theory, with Darwin, only to have the theory credited to Darwin because Darwin had all the evidence!
Alfred Russell Wallace

17. 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”

18. 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

19. 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

20. 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)

21. 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

22. Problems with the Theory
2. He could not show a single example of evolution occurring today, i.e. evolution in progress.
- He missed a good example right under his nose: the Peppered Moths of the Manchester Forest.