1. What factors have caused the evolution and diversity of organisms?
You plant a packet of zinnia seeds, and later, the zinnias begin to bloom. You notice that no two plants are exactly alike.
For example, some flowers have different colors than others. What accounts for these differences? Write an explanation.

2. Identify Multiple Meanings
Word
Everyday Meaning
Scientific Meaning
n. A guess; an idea of how or why something might happen
n. A well-tested concept that
explains a wide range of observations
theory
Example: Emily has a theory that basketball is harder to play than baseball.
Example: The cell theory says that all organisms are made of cells.

3. Apply It! In the sentences below, identify which meaning of the word
theory was used—the everyday meaning or the scientific
meaning.
The theory of evolution explains how organisms have changed over time.
Theory (science use)
Do you have a theory about why Sarah is a vegetarian?
Theory (everyday use)

4. Section 1: Darwin’s Theory
Changes Over Time
Section 1: Darwin’s Theory
What important observations did Darwin make on his voyage?
How did Darwin account for the diversity of species and the differences between similar species?
How does natural selection lead to evolution?

5. Darwin’s Voyage Changes Over Time
Charles Darwin sailed on the Beagle, from England to the Galápagos Islands.

6. Darwin’s Discoveries
Comparisons to South American Organisms: 1. many island species were similar to mainland species. 2. species were different because of what they had to eat. Comparisons among the islands: 1. Species varied from island to island. Adaptation: A trait that helps an organism survive & reproduce.

7. EVOLUTION
Darwin’s Reasoning: Species gradually changed over many generations & became better adapted to the new environments. Evolution- the gradual change in a species over time Scientific Theory- a well-tested concept that explains a wide range of observations. Selected Breeding- (used by breeders) selecting to breed species for certain traits (ex. Speed in race horses)

8. Overproduction and Variation
Changes Over Time
Overproduction and Variation
Natural selection is the process by which individuals who are better adapted to their environment are more likely to survive and reproduce than other members of the same species.
Overproduction:
Producing a lot of offspring.
Variation:
Differences in traits within a species.

9. Competition and Selection
Changes Over Time
Competition and Selection
Variations among turtles make some of them better able to survive. Turtles that survive to become adults will be able to reproduce.
Selection:
“survival of the FITTEST”.
Competition:
Species compete against each other to survive.

10. Environmental Factors: can effect an organism’s ability to survive. (ex. Pollution, hunting) Genes and Natural Selection: genes contribute to natural selection.

11. Links on Charles Darwin
Changes Over Time
Links on Charles Darwin
Click the SciLinks button for links on Charles Darwin.

12. End of Section: Darwin’s Theory (write summary)
Changes Over Time
End of Section: Darwin’s Theory (write summary)

13. Section 2: Evidence of Evolution
What evidence supports the theory of evolution?
How do fossils form?
What do scientists learn from fossils?

14. Forms of Evidence Body Structure
Comparative Anatomy- comparing body structures of different organisms.
Homologous structures- similar structures that related species inherited from common ancestor.

15. Homologous Structures
The structure of the bones in a dolphin’s flipper, a bird’s wing, and a dog’s leg is similar. Homologous bones are shown in the same color.

16. Other Similarities:
Similarities in Early Development- comparing how different species develop before birth.
Similarities in DNA & Proteins-
Similar DNA = common ancestor

17. A variety of species
Over time, different environments and genetic variation have produced, through natural selection, the variety of organisms that exist today. Different Environments: habitat: specific environment that provides the things organisms need to LIVE, GROW & REPRODUCE. Genetic Diversity: species are not completely identical. -variations & mutations

18. How do New Species Form?
New species can form when a group of individuals remain isolated from the rest of it’s species long enough to evolve different traits. How? Geographic Isolation- when some members of a species become cut off from the rest.

19. Kaibab and Abert’s Squirrels
These two kinds of squirrels have been isolated from one another for a long time. Eventually this isolation may result in two different species.

20. Inferring Species Relationships
Similarities in DNA- species inherited many of the same genes from common ancestors. Combining Evidence- Similar DNA + Protein structure = common ancestor

21. A Branching Tree
This branching tree shows how scientists now think that raccoons, lesser pandas, giant pandas, and bears are related. Related by shared-derived characteristics.

22. Extinction of Species
Extinction is caused by a change in species' environment. The members of a species may not have adaptations that allow them to survive and reproduce in the changed environment.
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23. Extinction and the Environment
Extinct: When no members of that species are still alive
This is caused by the species environment
New disease
Predators
Hunting
Climate Change- the leading cause of extinction
Adaptation and Survival-
Some organisms have traits that will help them adapt to the new environment and survive.

24. A Branching Tree
Branching tree diagrams such as this show relationships between groups of organisms. It also shows the order in which specific characteristics may have evolved.

25. Shared Derived Characteristics
A branching tree diagram shows evolutionary relationships by grouping organisms according to shared derived characteristic, a homologous structure shared by all in a group.
Reptiles
Amphibians
Fishes
Egg with shell
Invertebrates
Four limbs
Backbone
Ancestor of animals

26. Order of Characteristics Evolutionary Groups
The lower on the branch, the earlier it developed
Groups within groups
Reptiles
Amphibians
Fishes
Egg with shell
Invertebrates
Four limbs
Backbone
Ancestor of animals
Largest subgroup

27. Constructing a Branch Tree
Group with 2 shared traits
Group with 1 shared trait
Group with none of characteristics
Shared trait
Shared trait
Shared trait
Common ancestor