1. Evolution
Chapter 15

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 – other 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. Natural Selection Questions (Bill Nye)
A young man that walked out was __ ___.
He quit medical school to become a ___.
How long did the Beagle stay in the Galapagos Islands? __ days
Finches had different shaped ___: varied by the environment they inhabited.
What was the mechanism that made evolution occur? ___ ____
When did he publish his book?
Now, every where we look at today, we see something that came from ___.

9. Natural Selection Clip (Bill Nye)

10. An Ancient, Changing Earth
James Hutton and Charles Lyell
Recognized that Earth is many millions of years old.
And the processes that changed Earth in the past are the same processes that operate in the present.

11. Hutton and Lyell
Volcanoes release hot lava and gases now, just as they did on an ancient Earth.
Erosion continues to carve out canyons, just as it did in the past.
Also said that awesome geological features could be built up or torn down over long periods of time.
(examples: earthquakes and volcanoes)
Darwin then asked:
If the Earth could change over time,
might life change as well?

12. Lamarck’s Theory of Evolution
Proposed that by selective use or disuse of organs, organisms acquired or lost certain traits during their lifetime.
These traits could then be passed on to their offspring.
Over time, this process led to change in a species

13. Lamarck Continued Fiddler Crabs: An Example
1. The male crab uses its small front claw to attract mates and ward off predators
2. Because the front claw has been used repeatedly, it becomes larger.
3. A larger claw, is then passed on to the crab’s offspring.
He was WRONG! He did not realize that the large claw traits were inherited

14. Lamark’s Theory
According to Lamarck's theory, a given giraffe could, over a lifetime of straining to reach high branches, develop an elongated neck.
The long neck is ACQUIRED

15. Population Growth
Malthus (an economist) – observed that babies were being born faster than people were dying.
He reasoned that if the human population continued to grow unchecked, sooner or later there would be insufficient living space and food for everyone.

16. Carrying Capacity
The largest number of individuals of a population that a given environment can support.

17. 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 year.

18. 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.

19. 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.

20. Evolution by Natural Selection
The Struggle for Existence: Means that members of each species compete regularly to obtain food, living space, and other necessities of life.
A predator that is the fastest or has a particular way of catching prey can catch more prey.
Prey that are faster, better
camouflaged, or better protected
avoid being caught.

21. 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.

22. Darwin’s Discoveries Video Clip

23. 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.

24. 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.

25. 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.

26. 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

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

28. Evidence of Evolution
Homologous Structures: Structures that have different mature forms in different organisms but develop from the same embryonic tissues.

29. Evolution

30. Evidence for Evolution
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

31. Evidence of Evolution
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

32. 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.

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

34. Evidence of Evolution
Comparative Biochemistry- the more closely related species are the greater the number of amino acid sequences will be shared.
Geographic distribution-distributions of fossils and living organisms found around the world.

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

36. Adaptations: Camouflage: Adaptation that allows organisms to blend
into their surrounds.

37. Adaptations
Bacterial resistance: species of bacteria have developed drug resistance.

38. The End