1. Evolution
Changes Over Time

2. Evolution
What have you heard?
Facts vs. Myths

3. Charles Darwin Charles Darwin was a British naturalist.
Naturalist: someone who studies nature
He sailed around the world on his ship The Beagle and learned about plants and animals from different lands.

4. Darwin’s Travels

5. Galapagos Islands A group of islands off the coast of South America
Darwin observed great diversity among organisms

6. Darwin’s Discoveries iguanas finches tortoises
He noticed that all of these types of organisms appeared on each of the islands, but they looked and acted very differently from one another. He developed a theory as to why the finches and other organisms looked different…Natural Selection.

7. Darwin’s Finches
Finches ( a small bird) were also very different from island to island.
Each finch was specially designed to the food it ate

8. Variation All individuals are different because of their genetic code
Some variations help an individual survive & others do not
If they survive they will reproduce more individuals with that trait

9. Finch Beaks Finches that ate insects had a needlelike beak.
seeds had a strong,
wide beak.
Discovery Education

10. Adaptations Beak shape is an example of an adaptation.
Adaptation- a structure or behavior that helps an organism to survive and reproduce in it’s environment.

11. Natural Selection
Natural Selection: the survival and reproduction of individuals with traits that enable them to better survive in their environment.

12. Thinker!
If a group of birds with thin, long beaks and a group of birds with thick, heavy beaks live on an island where only seeds are available, What type of birds will survive?
The birds with thick, heavy beaks.
What will happen to the birds with thin, long beaks?
That group will eventually die off! = extinction

13. Mutations Inheritable changes in the DNA
Can result in favorable changes that allow species to adapt
Those species will live to reproduce
Some mutations create unfavorable changes in individuals
Those species will become extinct.

14. Do these changes happen in organisms today???
Adaptations in Action
Do these changes happen in organisms today???
Bacteria: becoming resistant to antibiotics
Hunting: elephants born without tusks were not valuable to poachers…therefore their numbers increased and the numbers of those with tusks decreased.
Insecticide Resistance: insects are adapting to the use of certain chemicals in pesticides

15. Changes over time
Evolution: the gradual change of a species over time.
How can a species change over time?

16. Natural Selection & Evolution
Over a long period of time, natural selection can lead to evolution.
Helpful variations gradually accumulate in a species, while unfavorable ones disappear.
Organisms with those traits become extinct: no longer exist

17. Evolution
Darwin's ideas are often referred to as the theory of evolution.
A scientific theory is a well-tested idea to explain observations. (Not just a guess)
There is a lot of other evidence for evolution
The fossil record
Radiometric dating
Genetic Information
Similarities and differences in anatomy

19. Fossils
A fossil is a preserved record of an organism that lived in the past
Bone, teeth, & shells
Footprints or burrows
Scientists can learn a lot about the Earth’s past by looking at fossils (like a detective!)

20. How do Fossils Form?
When an animal dies the soft parts of the body decay or are eaten
The remains get buried in sediment (soil & rock)
Over a long time the sediment harden to form a fossil!

21. Reading the Fossil Records
Fossils can show how organisms in the past are different from organisms today!
The oldest layer is on the bottom

22. Determining the Age of Fossils
Relative Dating
Absolute Dating
Used to determine which fossils are older
Top layers of rock formed last = youngest
Determines actual age by radioactive dating
Rocks contain elements that decay over time
Age of a fossil can be determined by how much of certain elements are left

23. Molds & Casts Mold Cast The empty space left in the rock
When a mold gets filled with hardened minerals

24. The Fossil Record
Fossils help scientist piece together the Earth’s past
The collection of fossils scientists have found is called the fossil record.
Still Gaps!
Most fossils are of extinct organisms: no longer alive

25. Evidence for Evolution
By studying fossils, scientists have learned how organisms have changed over time!
Ex: First organisms lived in water, & after plants produced enough oxygen, animals began to live on Earth!

26. Homologous Structures
Homologous Structure: a similar body part the species may have inherited from a common ancestor.
Shows that some organisms may have evolved from a common ancestor

27. Similar Development
During early development organisms go through similar changes
Can show how closely related organisms are

28. Similar DNA
Scientists are also studying DNA to see how closely related organisms are.
The closer the sequence the more closely related
Scientists can now take DNA from fossils

29. Combining the Evidence
Scientists have used evidence to construct evolutionary trees:
diagrams that show evolutionary relationships among the different groups of organisms.