1. Chapter 15 Darwin’s Theory of Evolution

2. 15-1 The Puzzle of Life’s Diversity
The variety of organisms is called biological diversity. How did all these different organisms arise? How are they related?
- Evolution = change over time
- Theory of evolution = a collection of scientific facts, observations and hypotheses

3. Voyage of the Beagle
- Charles Darwin – made numerous observations and collected evidence that led him to propose a revolutionary hypothesis about the way life changes over time.
– He sailed on the HMS Beagle around the world
- Observed & collected plant and animal specimens

4. Darwin’s Voyage

5. Darwin’s Observations
- He saw variety in traits, method of reproducing, where they live
- He saw fossils and compared to current living organisms in area
- Galápagos Islands – 1000 km west of S. America
- islands had different climates and slightly different organisms

6. The Journey Home
Giant Tortoises of the Galápagos Islands
Pinta
Tower
Pinta Island Intermediate shell
Marchena
James
Fernandina
Santa Cruz
Isabela
Santa Fe
Hood Island
Saddle-backed shell
Floreana
Hood
Isabela Island
Dome-shaped shell
Darwin observed that the characteristics of many animals and plants varied noticeably among the different Galápagos islands

7. Galapagos organisms Galapagos tortoise Marine Iguana Frigate bird
Albatross

8. 15-2 Ideas That Shaped Darwin’s Thinking
An Ancient, Changing Earth
Hutton and Lyell (geologists) helped scientists recognize 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.

9. 15-2 Ideas That Shaped Darwin’s Thinking
Lamarck’s Evolution Hypothesis
- Jean-Baptiste Lamarck ( French naturalist) 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.

10. - Organisms have tendency towards perfection.
- Organisms can alter traits.
- New traits can be passed to offspring.
- Ex: If you lift weights to build muscle, your children will be born with big muscles.
- This theory has been disproved by many experiments and observations.

11. Figure 15–7 Lamarck’s Theory of Evolution
Male uses small claw to attracts mates and wards off predators.
Front claw becomes larger through use.
The acquired characteristic, a large claw, is passed to offspring.

12. Population Growth
Thomas Malthus (economist) reasoned that if the human population continued to grow unchecked, sooner or later there would be insufficient living space and food for everyone.

13. 15-3 Darwin Presents His Case
Darwin discovered that the Galápagos Islands were home to species that are found nowhere else, but similar to organisms from S. America.
Publication of On the Origin of Species
- Darwin proposed a mechanism for evolution called natural selection in the book On the Origin of Species 1859

14. Evolution by Natural Selection
- Struggle for existence = Darwin observed high birth rates and a shortage of basic needs cause competition
- Fitness = the ability of an individual to survival and reproduce in its environment

15. - Adaptation = an inherited characteristic that increases an organism’s chance of survival
1. structural = porcupine’s sharp quills
2. physiological = the way a plant does photosynthesis
3. behavioral = how animals live and hunt in groups

16. - Process of survival of the fittest:
1. Individuals in a population compete for resources
2. Those with characteristics best suited to the environment survive and reproduce… pass on the beneficial characteristics
3. Over many generations, the beneficial characteristics appear in more members
- Ex: Peppered moths of Manchester

17. - Common descent – principle that all species, living and extinct, were derived from common ancestors

19. Evidence of Evolution
- Fossil record – fossils from deeper rock layers are older than fossils from shallower layers
- Geographic distribution of living species – Darwin saw many different species of finches in Galápagos Islands… descended with modification from a common mainland ancestor

20. Figure 15–14 Geographic Distribution of Living Species
Beaver
Beaver
Muskrat
Beaver and Muskrat
Coypu
Capybara
Coypu and Capybara
NORTH AMERICA
Muskrat
Capybara
SOUTH AMERICA
Coypu

21. - Homologous Body Structures – structures that have different mature forms but develop from the same embryonic tissues
- Ex: limbs of reptiles, birds and mammals are constructed from same basic bones
- Scientists can compare how similar the bones are to find degree of relations

22. Figure 15–15 Homologous Body Structures
Turtle
Alligator
Bird
Mammal
Ancient lobe-finned fish

23. - Vestigial organs = organs that are reduced in size and resemble homologous organs of other species
- Ex: legs of skinks (lizards), appendix and tailbone of humans, snakes and whales have femur and pelvis bones

24. Vestigial Organs

25. - Embryology – The early stages, or embryos, of many animals with backbones are very similar

27. Concept Map Evidence of Evolution includes The fossil record
Geographic distribution of living species
Homologous body structures
Similarities in early development
which is composed of
which indicates
which implies
which implies
Physical remains of organisms
Common ancestral species
Similar genes

28. Summary of Darwin’s Theory
- Individuals differ… variation is heritable
- More offspring are born than can survive
- Organisms compete for limited resources
- Organisms best suited for the environment live, reproduce, and pass on traits… natural selection
- Species have descended with modification from common ancestors

29. Strengths and Weaknesses of Evolutionary Theory
- Questions as to precisely how new species arise
- Uncertainty in how life began