1. Theory of Evolution
Chapter 15

2. The History of Evolutionary Thought
The development of new types of organisms from preexisting types of organisms over time.
Also could be described as a heritable change in characteristics within a population from one generation to the next

3. The History of Evolutionary Thought
Darwin’s Ideas
Used the phrase “descent with modification” to describe the process of evolution
Every species, living or extinct, must have descended by reproduction from preexisting species and that species must be able to change over time.

4. Theory of Natural Selection (Darwin)
1. Overproduction
More offspring are produced than can survive to maturity
2. Genetic Variation
Within a population, individuals have different traits. Ex: Thick fur
Occasionally, new traits may appear in a population

5. Theory of Natural Selection (Darwin)
3. Struggle to Survive
Individuals must compete with each other
Some variations improve an individuals chances to reproduce, but some variations reduce this chance.
4. Differential Reproduction
Organisms with the best adaptations are likely to survive and reproduce
Through inheritance, the adaptations will become more frequent in the population

7. Evidence of Evolution
Fossil – the remains or traces of an organism that died long ago.
Show that different types of organisms appeared at different times and places on earth.

8. Superposition – this principle states that if the rock strata at a location have not been disturbed, the lowest stratum was formed before the strata above it.

9. The Geologic Time Scale
Geologists put together a timeline for the order in which different groups of rocks and fossils were formed.
The Geologic Time Scale
Relative age – its age compared to that of other fossils.
Absolute age – more accurate using radiometric dating
Not all fossils are discovered and not all remains become fossilized

10. Distribution of Fossils
Different organisms lived at different times
Today’s organisms are different from those of the past
Fossils found in adjacent layers are more like each other than fossils found in deeper or higher layers.
By comparing fossils and rocks from around the planet, we can infer when and where different organisms existed.
Species have differed in a gradual sequence of forms over time.

12. Transitional Species
Have features that are intermediate between those of hypothesized ancestors and later descendant species.
Example – Page 304

13. Anatomy and Embryology
Homologous structures – anatomical structures that occur in different species and that originated by heredity from a structure in the most recent common ancestor of the species.

14. Anatomy and Embryology
Analogous structures
have closely related functions but do not derive from the same ancestral structure.

15. Anatomy and Embryology
Vestigial structures – seem to serve no function but that resemble structures with functional roles in related organisms.

16. Anatomy and Embryology
The development of animal embryos is also evidence of descent with modification

17. Biological Molecules
Biologists can compare the DNA, RNA, proteins, and other biological molecules from many different organisms.
They can then look for similarities and differences among the data for each species
The greater the number of similarities between any given species, the more closely the species are related through a common ancestor.

18. Developing Theory

19. Evolution in Action
Convergent Evolution – process by which different species evolve similar traits.

20. Divergent Evolution – process in which the descendants of a single ancestor diversify into species that each fit different parts of the environment.

21. Adaptive radiation – sometimes, a new population in a new environment, such as an island, will undergo divergent evolution until the population fills many parts of the environment

22. Artificial Selection
this process occurs when a human breeder chooses individuals that will parent the next generation.

23. Co-evolution
when two or more species have evolved adaptations to each other’s influence.
Ex: Bacteria and humans – resistance