1. The Theory of Evolution by Natural Selection

2. Introduction
Evolution – includes all of the changes in the characteristics and diversity of life that occur throughout time.
Evolution can occur on both large and small scales.
Microevolution
Macroevolution

3. Evolution of Evolutionary thinking (Pre-Darwinian)
Jean-Baptiste Lamarck ( ) – French naturalist, proposed a theory that organisms were driven by some inner force toward greater complexity. But thought that org. could pass on traits to their offspring that they acquired during their lives. (“Lamarckism”, proposed in 1809)

4. Lamarckism
Lamarck based his theory on two observations thought to be true in his day:
“Use it or lose it” - Individuals lose characteristics they do not require and develop those which are useful.
Inheritance of acquired traits - Individuals inherit the acquired traits of their ancestors.

5. This theory was later disproved!
Lamarckism
Examples include: the stretching by giraffes to reach leaves leads to offspring with longer necks;
Strengthening of muscles in a blacksmith's arm leads to sons with like muscular development.
This theory was later disproved!

6. Darwin’s Voyage Charles Darwin Set sail on the HMS Beagle in 1831
Became the ship’s naturalist
Arrived in the Galapagos Islands in 1835
Observed that the animals on the islands were similar to those on the mainland

7. Darwin’s Voyage Galapagos Animals
The Galapagos animals, while similar, were also different from island to island as well as to the mainland
Most obvious difference were the sizes and shapes of the finches’ (small birds) beaks
Sizes and shapes of the beaks were adapted to what the birds ate

8. Galápagos Finches Beak shape varies depending on diet Berry eater
Seed eaters
Cactus eaters
Insect eaters

9. Darwin’s Voyage On the Origin of Species (Darwin’s book)
For the 20 years that followed his return to England Darwin studied plants, animals and adaptations
Darwin wrote about how species can change gradually over many, many generations and become better adapted to new environmental conditions.

10. Evolution
The gradual change in a species over time.

11. Natural Selection
Organisms that are better adapted to an environment are more likely to survive and reproduce than organisms that are less well adapted.

12. Adaptations Katydids have camouflage to look like leaves.
Non-poisonous king snakes mimic poisonous coral snakes.

13. Factors that affect Natural Selection:
Overproduction most species produce far more offspring than will/can survive
Overproducers
Producers
mature rapidly 
mature slowly
short-lived: most die before they reproduce
live long lives: low juvenile mortality rate 
have many offspring - tend to overproduce
have few offspring at a time
invest little in individual youngsters 
care for their young
population not regulated by density: boom and bust population figures
population stabilizes near carrying capacity

14. Factors that affect Natural Selection:
Competition: since food and resources are limited, the offspring have to compete to survive Darwin called it: “Struggle for existence”

15. Factors that affect Natural Selection:
Variation: Members within a species exhibit individual differences – these differences must be inheritable Natural selection won’t work in a population of clones! Remember that a key to variation is sexual reproduction.

16. Natural Selection
In any population of organisms there is natural variation.
Some of these variations will allow the organisms possessing them to survive and reproduce better than those without these particular traits.

17. Factors that affect Natural Selection:
Survival to reproduce: Only those individuals that are better suited to the environment will survive and reproduce (“Survival of the fittest”). Fit individuals pass on to a portion of their offspring the advantageous characteristics.

18. How do new species form? Natural Selection Continental Drift
Changes in environment
Mutations
Man

19. Continental Drift
Fossil records show that when the continents were connected animals walked across. When the continents separated, the animals were separated.

20. Changes in the Environment
Example, the pepper moth. Originally, the pepper moth was white, which was good because it could blend in. Then, trains were invented and the soot they produced covered the trees. Making the trees black. The moths that were black could now survive better.

21. Mutations
Some species are more susceptible to mutations. Some mutations allow the animal to survive; other mutations do not allow the animal to survive. The mutations that are not decrease the chance of survival remain.

22. Man: Artificial Selection
Selective breeding as practiced by humans on domesticated plants and animals….
For example: Dogs

23. Evidence of Evolution Fossil Record Similarities in Body Structure
Similarities in Early Development
Vestigial Structures
Similarities in DNA

24. Fossil Record How fossils form
An organism dies and becomes buried in sediment
Minerals gradually replace the bones and more sediments cover the fossil
Pterodactyl
Trilobite

25. Stratigraphy
Fossils from organisms that died longer ago are buried deeper in the sediment/rock than fossils from organisms that died more recently.

26. Similarities in Body Structure “Homologous structures”
If the two organisms have body structures that are similar, they must have had a common ancestor.

27. Similarities in Early Development
Scientists look at embryos of different organisms and find that many embryos resemble one another.

28. Vestigial Structures
Vestigial Structures A structure found in an organism that is no longer in use but may have been useful at some point in the organism's life.
Whales possess a femur and pelvis, but these bones are no longer useful to the mammals.
Tail Present in human and all vertebrate embryos. In humans, the tail is reduced; most adults only have three to five tiny tail bones and, occasionally, a trace of a tail-extending muscle.

29. Vestigial Structures
Why do dogs have tiny, functionless toes on their feet (dewclaws)?
Ancestral dogs had five toes on each foot

30. Similarities in DNA
The more similar the sequences of DNA are, the more closely related the organisms are.
Humans and chimpanzees DNA is more similar than human DNA is to dog DNA.