1. Theory of Evolution
Chapter 15

2. 15.1 Key Concepts What was Charles Darwin’s contribution of science?
What pattern did Darwin observe among organisms of the Galapagos Islands?

3. 15-1 The Puzzle of Life’s Diversity
Biological diversity- variety of living things
How did they arise? Related?
Evolution- change over time; process by which modern organisms have descended from ancient organisms
Theory- well-supported testable explanation of phenomena that have occurred in the natural world

4. Charles Darwin Charles Darwin (1809-1882)- Englishman
Voyage aboard H.M.S. Beagle (1831)
During his travels, Darwin made numerous observations and collected evidence that led him to propose a revolutionary hypothesis about the way life changes over time
Collected plant and animal specimens while ship was anchored

5. Darwin’s Observations
Well suited for environment
Many ways for survival and production of offspring
Puzzled by where species lived and did not live
Gathered fossils
Resembled organisms still alive
Others looked completely different
Galapagos Islands were very close together, but had very different climates
Tortoise shells

6. Journey Home Time spent thinking
Darwin observed that the characteristics of many animals and plants varied noticeably among the different islands of the Galapagos

7. 15-2 Ideas That Shaped Darwin’s Thinking
Fossils caused Darwin to be skeptical of people’s views
Earth created only a few thousand years ago
Robin had always been a robin
Discoveries challenged fundamental beliefs held at that time

8. Lyell and Hutton James Hutton Charles Lyell
Earth had to be much more than a few thousand years old
1795, hypothesis about geological forces that have shaped Earth
Internal forces- mountains, valleys, rocks- affected by natural forces- rain, wind, heat and cold temps
Charles Lyell
Gave book to Darwin
Processes that shaped the Earth millions of years earlier continue in present
Fossils of marine animals above sea level
Influence?: If the Earth could change over time, might life change as well?
It would have taken many, many years for life to change in the way he suggested. This would have been possible only if the Earth were extremely old

9. Jean- Baptiste Lamarck
Living things have changed over time
1809- hypothesis (1st to develop)
Tendency toward perfection- continually changing and acquiring features that help them live more successfully in their environments
Use and disuse- organisms could alter the size or shape of particular organs by using their bodies in new ways
Inheritance of acquire traits- pass on traits to offspring
Evaluation of hypothesis
Did not know how traits are inherited
Did not know that behavior has no effect on heritance

10. Thomas Malthus 1798- human population
Reasoned that if the human population continued to grow unchecked, sooner or later there would be insufficient living space and food for everyone
Influence
What causes death of so many individuals?
What factor/factors determine which ones survive and reproduce, and which do not?

11. 15-3 Darwin Presents His Case
1858- Alfred Wallace sent short essay which contained thoughts on evolutionary change
1859- Darwin publishes his book On the Origin of Species

12. Inherited Variation and Artificial Selection
Inherited variation- differences that are passed from parents to offspring
Larger fruits on plants; some cows give more milk
Today: caused by variations in their genes
Then: revolutionary idea because variations thought to be minor defects
Artificial selection- selection by humans for breeding of useful traits from the natural variation among different organisms
Animal breeders used heritable variation to improve livestock and crops

13. Evolution by Natural Selection
Malthus- high birth rates and shortage of life’s basic needs would eventually force organisms into a competition for resources
Survival of the Fittest
Fitness- ability of an individual to survive and reproduce in its specific environment
Result of adaptation- any inherited characteristic that increases an organism’s chance of survival
Can be anatomical (structural) or physiological (functions)

14. Evolution by Natural Selection
Central to process of evolution by natural selection
Individuals compete to survive and produce offspring
Low levels of fitness = death
High levels of fitness = survival
Survival of the fittest (natural selection)- process by which individuals that are better suited to their environment survive and reproduce most successfully (takes place without human control or direction)
Can only be seen in time over successive generations
Only certain individuals of a population produce new individuals

15. Descent with Modification
Principle that each living species descended with changes, from other species over time
Look different from ancestors
Implies that all living organisms are related to one another
Common descent- principle that all species were derived from common ancestors
“Tree of life” links all living things

16. Evidence of Evolution Fossil Record Geographic Distribution
Fossils = record of history of Earth
Compare fossils of older rock layers and fossils of younger rock layers told us that life on Earth has changed over time
# of fossils has increased since Darwin, but we still have gaps
Geographic Distribution
Finches- similar but distinctly different
Slightly different from mainland (S. America)
Same ancestor with modifications
Different species on continents of S. America and Australia
Similar environments = similar features; different ancestors

17. Evidence of Evolution Homologous Body Structures
Limbs vary greatly in form and function, yet constructed from same basic bones
Homologous structures- structures that have different mature forms but develop from the same embryonic tissue
Descent with modification
Group organisms to how recently they last shared a common ancestor
Vestigial organ- organ that serves no useful function in an organism

18. Embryology
Early stages, or embryos, of many animals with backbones are very similar
The same groups of embryonic cells develop in the same order and in similar patterns to produce the tissues and organs of all vertebrates

19. Summary of Darwin’s Theory
Individual organisms differ, and some of this variation is heritable
Organisms produce more offspring than can survive, and many that do survive do not reproduce
Because more organisms are produced than can survive, they compete for limited resources