1. An Introduction to Evolution: Charles Darwin, Evolutionary Thought, and the Evidence of Evolution

2. 16.1 Evolution and Its Core Principles

3. Common Descent with Modification
Species undergo modifications over time
Such change sometimes results in the formation of new, separate species.

4. Descent With Modification4 4

5. Common Descent with Modification
All species on Earth have descended from other species, and a single, common ancestor lies at the base of the evolutionary tree.

6. Natural Selection Natural selection
Traits in a population become more or less common over time because:
Individuals with favorable traits are able to survive, reproduce, and pass on those favorable traits to their offspring
Individuals with less favorable characteristics are not able to survive and reproduce and thus do not pass on their less favorable traits

7. 10. Natural Selection
The traits that help an organism survive in a particular environment are “selected” by nature

8. Importance of Evolution as a Concept
The theory of evolution has an importance beyond the domain of biology. Through it, human beings have become aware that:
They are descended from other varieties of living things.
The organisms that populate the living world are not fixed entities, but instead are constantly undergoing modification.

9. 16.2 Charles Darwin and the Theory of Evolution

10. Darwin and the Theory of Evolution
Figure 16.1

11. Darwin and the Theory of Evolution
Charles Darwin deserves primary credit for the theory of evolution.
He was the first to propose natural selection as the primary process that drives evolution.

12. Darwin and the Theory of Evolution
Darwin’s insights were inspired by the research he carried out during a five-year voyage he took around the world on the ship HMS Beagle, beginning in 1831.

13. Darwin and the Theory of Evolution
Figure 16.2

14. Darwin and the Theory of Evolution
Dec
Oct. 1836
Europe
Asia
North
America
Africa
Sept. 1835
Galapagos
Islands
equator
South
America
April 1832
Australia
Jan. 1836
July 1834
Falkland Islands
March 1833
March 1834
Figure 16.3

15. 16.4 Darwin’s Insights Following the Beagle’s Voyage

16. 3.How did tortoises and birds differ among the islands of the Galapagos?
Each island had its own type of tortoises and birds that were clearly different from other islands

17. 17 17

18. 18 18

19. Descent with Modification is Accepted
Figure 16.7

20. 16.7 Darwin Doubted: The Controversy over Natural Selection

21. Controversy over Natural Selection
Its acceptance hinged on a modern synthesis in the theory of evolution that brought together lines of evidence from genetics, the fossil record, and the distribution of organisms throughout the world.

22. Opposition to the Theory of Evolution
Even today, the theory of evolution is regularly challenged as being unproven or simply wrong.

23. Opposition to the Theory of Evolution
One factor leading to the appearance of a “scientific debate” over evolution is confusion about the meaning of the word theory.
Though the average person may equate “theory” with speculation, in science a theory is a general set of principles supported by a lot of evidence that explains some aspect of the natural world.

24. 16.9 The Evidence for Evolution

25. 1. Radiometric Dating
First, radiometric dating has confirmed the immense age of the Earth—an age that is consistent with the long periods of time scientists believe it has taken species to evolve.

26. 2. Fossils
Second, around the globe, fossils from the same evolutionary periods are consistently found together in geologic strata.

27. 2. Fossils
Moreover, there is excellent agreement between the relative ages assigned to fossils by evolutionary theory and the absolute ages assigned to them by radiometric dating.

28. 2. Fossils
Figure 16.10

29. 3. Comparative Morphology and Embryology
Third, the theory of evolution explains the common occurrence of homologous physical structures in different organisms.

30. 3. Comparative Morphology and Embryology
whale
cat
bat
gorilla
Figure 16.11

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

32. Embryology
Pharyngeal slits exist in these five vertebrate animals . . .
pharyngeal
slits
sea lamprey
pond turtle
chicken
domestic cat
human being
. . . evidence that all five evolved from a common ancestor
Figure 16.9

33. Embryological development

34. Vestigial Organs Organ that serves no useful function
ex. appendix, hip bones in whales, eyes in blind mole rats

35. Biochemistry
Provides evidence that all organisms come from a common ancestor
All organisms have in common:
DNA
ATP (energy molecule)
Enzymes, amino acids, proteins

36. 5. Evidence from Gene Modification
Fifth, variations found in the DNA sequences of various organisms are consistent with evolutionary theory.

37. 5. Evidence from Gene Modification
Number of DNA nucleotide base differences in the cytochrome c oxidase gene
Large number of
base differences
between humans
and yeast 66 36 31 20 17
Small number of
base differences
between humans
and pigs 13
human
pig
duck
snake
tuna
moth
yeast
Figure 16.14

38. Review All organisms come from a common ancestor
One tree of life—all living things connected
Fossil record
Homologous structures
Embryology
Biochemistry