1. CHANGES OVER TIME

2. Unit Preview
Darwin’s Theory
Evidence of Evolution
The Fossil Record

3. Darwin’s Theory
What important observations did Darwin make on his voyage?
What hypothesis did Darwin make to explain the differences between similar species?
How does natural selection lead to evolution?

4. Key Terms Adaptation - Evolution - Fossil -
A trait that helps an organism survive and reproduce.
The gradual change in a species over time.
The preserved remains or traces of an organism that lived in the past.

5. Key Terms Natural Selection - Scientific Theory - Species -
Variation -
Individuals that are better adapted to their environment are more likely to survive.
A well-tested concept that explains a wide range of observations.
A group of similar organisms that can mate with each other and produce offspring.
Any difference between individuals of the same species.

6. Charles Darwin A “naturalist” – studied the natural world.
Sailed on the Beagle to the Galapagos Islands.
Observed many unusual organisms on the island.
Giant tortoises
Blue-footed booby
Galapagos finches

7. The Voyage of the Beagle
The Beagle made many stops along the coast of South America stopping at the Galapagos Islands.
Darwin observed living things as he traveled and tried to make connections about the relationships among those organisms.
Diversity of living things
Remains of ancient organisms
Unique characteristics of organisms on the Galapagos.

8. Darwin’s Observations
The theory of EVOLUTION by NATURAL SELECTION
Evolution
The gradual change in a species over time.
Natural Selection
Individuals that are better adapted to their environment will survive and reproduce.

9. DIVERSITY The variety of life on Earth.
Darwin was amazed by the tremendous diversity of living things that he saw.
Scientists have identified more than 1.7 million species of organisms on Earth.

10. FOSSILS
The preserved remains or traces of an organism that lived in the past.
Darwin was puzzled by some of the fossils he observed.
He saw fossil bones of animals that had died long ago but yet resembled the bones of organisms alive in Darwin’s time.

11. Galapagos Organisms
Darwin observed many unusual life forms on these small islands.
He compared Galapagos organisms to organisms that lived elsewhere.
He also compared organisms on different islands in the Galapagos group.
He tried to make connections using the similarities and differences he observed.

12. Comparisons to South American Organisms
The Galapagos organisms resembled many of those in South America.
Important differences between the organisms on the islands and those on the mainland were important in determining how the species ended up on the islands.
Darwin hypothesized that a small number of different plant and animal species had come to the Galapagos Islands from the mainland.
Blown out to sea during a storm
Set adrift on a fallen log
Once on the islands, the organisms reproduced and over time, their offspring became different from their mainland relatives because of their environment.

13. IGUANAS The iguanas on the Galapagos Islands had large claws.
Grip slippery rocks
Feed on seaweed
The iguanas on the mainland had smaller claws.
Climb trees
Eat leaves

14. Comparisons Among the Islands
Darwin noticed many differences among organisms as he traveled from one island to the next.
Darwin was able to identify which island an organism came from just by looking at it.

15. TORTOISES Some had dome-shaped shells. Some had saddle-shaped shells.
Tortoises lived inland and became like “land-dwelling mammals” grazing on vegetation.

16. GALAPAGOS FINCHES
Each species was well ADAPTED (suited) to the life it led.
Beak shape was based on their diet.
Narrow, needle-like beaks = insects
Strong, wide beaks = seeds

17. Adaptive Radiation
The evolutionary diversification of a single lineage into a variety of species with different adaptive properties.

18. Theory of Evolution
Darwin spent 20 years consulting with other scientists, gathering more information, and re-evaluating his observations from his trip on the Beagle before he developed his theory of evolution.
Plants or animals faced with different conditions will gradually change over many generations in order to become better adapted to their conditions.

19. Selective Breeding
The process of selecting a few organisms with desired traits to serve as parents of the next generation.
By repeatedly allowing only organisms with the desired traits to reproduce, the more desirable trait becomes common and highly favorable in the offspring.
Darwin made connections between the practice of selective breeding and organism behavior in nature as evidence for his theory of evolution.

20. Natural Selection
In 1858, Darwin proposed an explanation for how evolution could occur in nature.
Evolution occurs by means of NATURAL SELECTION.

21. Natural selection is the process by which individuals that are better adapted to their environment are more likely to survive and reproduce than other members of the same species.

22. Factors Affecting the Process of Natural Selection
Overproduction
Variations
Competition
Selection
Environmental change
Genes

23. OVERPRODUCTION
Most species produce far more offspring than can possibly survive.
A large number of offspring creates competition for resources.

24. VARIATIONS
Members of a species differ from one another in many of their traits.
Variations are linked to environmental conditions.

25. COMPETITION
Limited resources creates competition among members of a species.
Direct
Physical fights
Indirect
Searching for food
Avoiding predation

26. SELECTION
Some variations make individuals better adapted to their environment.
Individuals who are better adapted survive and reproduce.
Helpful variations may gradually accumulate in a species, while unfavorable ones may disappear.

27. ENVIRONMENTAL CHANGE
A change in the environment can affect an organism’s ability to survive.
The environmental change can gradually lead to selection.
The Galapagos Islands are a prime example of how the environment can lead to the evolution of a species by natural selection.

28. GENES
Without variations, all the members of a species would have the same traits.
Natural selection would not occur because all the individuals would have an equal chance of surviving and reproducing.
Variations can result from mutation and the shuffling of alleles during meiosis.
Genes are passed from parents to offspring.

29. . . . Survival of the Fittest!
Natural Selection . . .
. . . Survival of the Fittest!