1. Evolution

2. Evolution
Evolution, or change over time, is the process by which modern organisms have descended from ancient organisms.

3. Voyage of the Beagle Charles Darwin – born in England
Joined the crew of the
H.M.S. Beagle
Sailed around the world
Made numerous observations
and collected evidence that
led him to propose his
hypothesis.

4. Darwin’s Observations
Patterns of Diversity:
Puzzled by where different species lived and did not live
Asked:
Why were there no rabbits in Australia,
despite the presence of habitats that
seemed perfect for them?
Why were there no kangaroos in England?

5. Darwin’s Observations
Living Organisms and Fossils
Darwin collected and preserved fossils
Fossils resembled organisms that were still alive – others looked completely unlike any creature he had ever seen.
He Asked: Why had so many of these species
disappeared?

6. Darwin’s Observations
The Galapagos Islands
Most influenced Darwin
Although islands were so close together, the islands had very different climates.
Fascinated by the land tortoises and marine iguanas.

7. Darwin’s Observations
Galapagos Islands continued
Saw that giant tortoises varied in predictable ways from one island to another.
The shape of a tortoise’s shell could be used to identify which island a particular tortoise lived.

8. The Origin of Species by Means of Natural Selection
The actual title is:
The Origin of Species by Means of Natural Selection
The book proposed a mechanism for evolution that he called natural selection.
Presented evidence that demonstrating the process of evolution has been taking place for millions of years.

9. Natural Variation and Artificial Selection
Darwin’s Arguments
Natural Variation and Artificial Selection
Argued that species were not perfect and unchanging.
Natural Variation: There are differences
among individuals of a species.
Examples:
Some cows gave more milk than others & some plants bore larger fruit than others.

10. Darwin’s Arguments Natural Variation and Artificial Selection
Artificial Selection: Nature provided the variation among different organisms, and humans selected those variations that they found useful.
* Only the largest hogs, fastest horses, and the cows that gave the most milk were selected to breed and produce offspring.

11. Evolution by Natural Selection
Survival of the Fittest: Process by which individuals that are better suited to their environment survive and reproduce most successfully; also called Natural Selection.
Darwin called the ability of an individual to survive and reproduce in its specific environment fitness.
An adaptation is any inherited characteristic that increases an organism’s chance of survival.

12. Survival of the Fittest
The concept of fitness, Darwin argued, was central to the process of evolution by natural selection.
Example:
Baby birds compete for food in the nest. The stronger bird may take food from the weaker siblings.

13. Evolution by Natural Selection
Descent with Modification: Principle that each living species has descended, with changes, from other species over time.
Implies that all living organisms are related to one another.
Common Descent: The principle that says all species – living and extinct – were derived from common ancestors.

14. Evidence of Evolution Fossil Record
Fossils that had formed in the different layers of rock were evidence of gradual change over time.
One could view how a species had changed and produced different species over time.

15. Homologous Body Structures
Homologous Structures: Structures that have different mature forms in different organisms but develop from the same embryonic tissues.

16. Similarities in Early Development
In their early stages of development, chickens, turtles, and rats look similar, providing evidence that they shared a common ancestry.

17. Analogous Structures
Analogous structures can be superficially similar in construction, but are NOT inherited from a common ancestor.
Example: The wing of an eagle & the wing of a insect have the same function (both enable the organism to fly) – but are constructed in different ways & from different materials.

18. Analogous Structures
* While analogous structures do not indicate close evolutionary relationships, they do show that functionally similar features can evolve independently in similar environments.

19. Vestigial Structures
Vestigial Structures are structures that are the reduced forms of functional structures in different species.
Examples:
1. Snake Pelvis: The pelvis is the attachment point for legs and is therefore nonfunctional in an animal without legs

20. Vestigial Structures
2. Kiwi Wing: The wings of kiwis are too small to be of any use in flight
3. Human Appendix: Important for digestion in many mammals, but of limited use in humans & some apes

21. Adaptations:
Mimicry: Adaptation in which one species evolves to resemble another species for protection or other advantages.

22. Adaptations: Camouflage: Adaptation that allows organisms to blend
into their surroundings.

24. Geographic Distribution of Living Species
Evidence of Evolution
Species now living on different continents had each descended from different ancestors.
However, because some animals on each continent were living under similar ecological conditions, they were exposed to similar pressures of natural selection.
They ended up evolving certain striking features in common.
This is called Convergent Evolution
Geographic Distribution of Living Species