1. Chapter 10: Principles of Evolution

2. What is Evolution?
Evolution is the process of biological change by which descendants come to differ from their ancestors
It is the central theme in all fields of Biology

3. Carolus Linnaeus
Developed a classification system for all types of organisms
Organisms were grouped by similarities but also reflected evolutionary relationships

4. Georges Louis Leclerc de Buffon
Proposed that species shared ancestors instead of arising separately
Suggested that Earth was much older than 6,000 years old which was the common belief at the time

5. Erasmus Darwin Charles Darwin’s grandfather
Proposed that all living things were descended from a common ancestor and that more-complex forms of life arose from less-complex forms

6. Early misconception by Jean-Baptiste Lamarck (1809)
Proposed all organisms evolved toward perfection and complexity
Use and Disuse of Organs Theory—organisms respond to their environment by developing new structures as needed
The more an organ was in use, the bigger it would become and vice versa
Inheritance of Acquired Traits—these traits are passed on to offspring
Ex. giraffes

7. Lamarck continued…

8. Lamarck cont.
In order for groups of organisms to have adapted over time, populations must have evolved rather than individuals.

9. Charles Darwin ( )
An English scientist who formed ideas that are now the basis of modern evolutionary theory
When he was 21, Darwin took an apprenticeship on a 5-year scientific voyage on the HMS Beagle
He was the unofficial naturalist on the ship collecting many specimens along the way

10. Darwin’s voyage (Page 277)
Darwin's journey
The Galapagos Islands, off the coast of Ecuador, became the focal point in Darwin’s observations

11. In 1859, Darwin published his theories and ideas in the book On the Origin of Species by Natural Selection

12. Variation is the difference in the physical traits of an individual from those of other individuals in the group to which it belongs
Can occur either among members of different species (interspecific) or same species (intraspecific)

13. Darwin believed that variation arose when species adapted to their surroundings.
An adaptation is a feature that allows an organism to better survive in its environment
An adaptation can lead to genetic change in a population over time

14. Artificial selection
Darwin also conducted many breeding experiments with pigeons and found that organisms with specific traits could be crossed to result in offspring that had those selected traits; this is called artificial selection
Humans are the selecting agent in artificial selection

15. In order for—artificial or natural—selection to occur, the trait must be heritable.
Heritability is the ability of a trait to be passed down from one generation to the next
Natural selection is a mechanism by which individuals that have inherited beneficial adaptations produce more offspring on average than do other individuals.
The environment (nature) is the selective agent

16. Four main principles to the theory of natural selection
Variation
Individuals in a population have varying characteristics
Overproduction
Organisms tend to produce more offspring than can survive to maturity
Adaptation
The traits of survivors will become more common in a population
Descent with modification
Surviving individuals tend to reproduce more than others

18. Overview of the Evolution Theory
Variation exists within the genes of every population or species (as a result of random mutation)
In a particular environment, some individuals of a population or species are better suited to survive (a result of variation) and have more offspring (natural selection)

19. Overview cont.
3. Over time, the traits that make certain individuals of a population able to survive and reproduce tend to spread in that population
4. There is a clear proof from fossils and many other sources that living species evolved from organisms that are extinct.

20. Natural selection acts on phenotypes or physical traits, rather than on genetic material itself.

21. Evidence for Evolution
Fossil Record
Geography
Embryology
Body Structures (Anatomy)
Biochemistry (Genes and Proteins)

22. Fossil Record
Fossils of animals show a pattern of development from early ancestors to their modern descendants
“Intermediate” (missing links) species show how organisms evolved new adaptations
Fossil Evidence Examples

26. Problems with fossils
It is difficult to find fossils of soft-bodied organisms with no hard parts that can be left behind
Organisms decay at different rates and may not leave any traces

27. Geography Shows similarities among species living on different areas
“Descent with
modification”

28. Embryology
Most embryos look very similar and have gill slits and tails.
This suggests a common ancestor.

29. Anatomy
Comparing structures of related organisms to find relationships between organisms
Ex. Homologous Structures
Comparing Primate Skeletons
Comparing common structures between unrelated organisms to find how natural selection affects organisms in similar environments
Ex. Analogous Structures

30. Homologous Structures
Have a common evolutionary origin
Similar structure but different functions

31. Analogous Structures
Structures that are similar in function but do not have a common evolutionary origin
Different structures but similar functions
Ex. Bird wing and an insect wing
Shows that different species evolved similar traits to overcome similar selective agents

32. Homologous structures versus Analogous structures

33. Vestigial Structures
A body structure that has no function presently but was probably useful to an ancestor
Even though the species does not need the feature, the structure is still passed on to offspring
Ex. Eyes on blind mole-rats, flightless wings on an ostrich, appendix/tonsils on humans

34. Biochemistry
As organisms evolve, the differences in the amino acids, DNA, and proteins they make should change gradually
The more amino acid differences there are between two organisms, the more distantly related they are