1. EVOLUTION:
Descent with
modification

2. Age of the Earth Scientists estimate Earth to be 4.6 billion years old
Does not look today as it once did,
nor do the organisms on it

4. Change over time Earth is very old! Has changed a great deal.
Different atmosphere
Different temp.
Collisions from outer space
Some organisms have stayed about the same as they were millions of years ago (sharks). Some have changed. Some have disappeared.

5. Adaptation
Traits that an organism uses to survive and reproduce in it’s environment. They are passed on from parent to offspring.
Example: How are Polar bears adapted to life in the Arctic? Why would they not be well adapted to life in Hawaii?
Can include structures or behaviors
Sea Turtles bury their eggs in the sand.
How is this behavior an adaptation?

6. Species
Living things that share the same characteristics and adaptations
Can mate with one another to produce offspring that are fertile (can reproduce)
Species have changed over time

7. Species change too…
Many different life forms have existed through Earth’s history
Evidence for this comes from fossils
Why do species change? Due to evolution
Small changes in a species because of natural selection add up over millions of years!
Mutations in an organism’s DNA, although most often bad, can sometimes result in an adaptation. If this mutation helps the organism survive it will be selected and passed on to its offspring.

8. Evidence! Key evidence to support evolution comes from fossils
Generally found in sedimentary rock (particles of sand, dust and soil form layers, with oldest at the bottom)
Fossils tell us that some species have died out, while some have changed greatly
Why??

9. Because of EVOLUTION “Descent with Modification”
Organisms change over time, to what suits their survival the best
Example: Giraffe

10. Must Have:
Overproduction (too many babies)
Variation (different traits
C "Struggle for Existence"
“Success = Reproduction
and passing on the trait”

11. C Giraffes with longer
necks get better food,
have more babies
(have an advantage in
the struggle for existence)
C Longer necks make more
long necks
(so that trait gets inherited)

12. Results:
Over time,
average neck
length increases

13. **Extinctions may occur, which allow others to take over
Other conditions:
**New species can form
**Extinctions may occur, which allow others to take over
*Extinction happens
when adaptations fail
to keep up with
changes to the
environment.
Okapi (relative of the giraffe)

14. How do New Species Form?

15. Steps to a New Species Separation Adaptation
Selection (reproductive isolation)

16. More evidence for evolution
1. Comparing Skeletons:
Different organisms have same basic structure = common ancestor

17. 2. Fossil Evidence
At first glance, whales may seem similar to fish. But whales have all the characteristics of a mammal.
Scientists believe that the ancient ancestor of whales was a land mammal. A more recent ancestor was a mammal that spent some time in water and some time on land.
There is fossil evidence to support this hypothesis.

20. Things that have been left over as evolution takes place.
3. Vestigial Structures
Physical structures or behavior that is no longer necessary for an organism to survive or reproduce in it’s environment.
Things that have been left over as evolution takes place.
Scientists
think that the
appendix may
be a vestigial
structure.
Vestigial
Structure
Vestigial
Structure

21. 4. Comparing DNA from different species
All organisms have the same type of DNA
Organisms that are more closely related have more similar sequences of DNA (example: humans and chimpanzees, only million base pair differences

22. 5. Embryonic Structures
Early in development all embryos look amazingly similar
Common ancestor?

23. Were you paying attention?
1. What is evolution?
2. Organisms are considered members of the same species if…. A. B.

24. Were you paying Attention Cont.
3. What are the 3 steps to speciation (the forming of a new species) 4. What are 5 examples of evidence in support of the Theory of Evolution?

25. Branching Tree Diagrams
Scientists use branching tree diagrams to show how they think organisms are related.
They are kind of like family trees.
They use fossil evidence, comparative anatomy (comparing skeletons), and DNA comparisons

26. Which animal is most closely related to whales?

27. Which groups of animals are still alive today?
How can you tell?
Why do the lines get wider or thinner?
What does the branching tree diagram tell us about snakes and lizards?