1. Unit 3: Evolution

2. How does the theory of evolution by natural selection demonstrate the scientific process?
Science relies on evidence to explain observations of the natural world
Evolution is a theory: a well-supported explanation based on many observations
NOT a law.

3. Evolution
The change in species over time

4. Geologic Time Scale

5. Geologic time scale: scale used by paleontologists to represent evolutionary time

9. Precambrian comes first
Radioactive dating has been used to assign specific ages to rock layers
Precambrian comes first
Covers 88% of Earth’s history

10. After Precambrian time, divisions of time are eras and period
Era: 3 time periods from Precambrian until present
Paleozoic: 544 mya 245 mya
Mesozoic: 245 mya to 65 mya
Cenozoic: 65 mya to present

11. Period: Eras subdivided into smaller units of time called periods
Ex. Mesozoic Era made up of 3 periods
Triassic, Jurassic, and Cretaceous

12. Mesozoic

13. Cenozoic

14. The Fossil Record Fossils= remains of ancient life
Comparing fossils in older/younger rock layers
Provides evidence about the history of life on Earth. It also shows how different groups of organisms have changed over time

16. Paleontologists: Scientists who study fossils
Make inferences about structure, what organisms ate, where they lived

19. More than 99% of all species that have ever lived on earth have gone Extinct: died out

20. How Fossils Form
Either the remains or some trace of its presence must be preserved
Most formed in sedimentary rock
Organisms sink to bottom and become buried in sediment

21. Interpreting Fossil Evidence
Relative Dating: Age of fossil determined by comparing its placement with that of fossils in other layers of rock
Does not provide absolute age

22. Index fossils: A fossil species that is easily recognized and must have existed for a short time but in a wide geographic range
Used to compare fossils

24. Radioactive dating
Radioactive dating: use of half-lives to determine age of a sample
Half-life: Length of time required for half of the radioactive atoms in a sample to decay

26. Comparative Anatomy

27. Homologous Body Structure
Homologous structures: structures that have different mature forms but develop from the same embryonic tissues
All 4 limbed vertebrates from common ancestor

28. Vestigial organs: organ that serves no useful function
Ex. Legs in skinks

29. Similarities in Embryology
Early stages of animals with backbones similar

30. Biogeography
Biogeography is the study of the distribution of species, organisms, and ecosystems in space and through geological time.

31. Geographic Isolation: Two populations are separated physically by geographic barriers such as rivers, mountains, or water

32. Scientific Explanations for the Origin of Life on Earth

33. Spontaneous Generation
living organisms from inanimate objects
Francesco Redi disproved spontaneous generation for large organisms by showing that maggots arose from meat only when flies laid eggs in the meat.
Louis Pasteur's 1859 experiment put the question to rest. He boiled a meat broth in a flask that had a long neck which curved downward, like a goose. The idea being that the bend in the neck prevented any particles from reaching the broth, while still allowing the free flow of air. The flask remained free of growth for an extended period. When the flask was turned so that particles could fall down the bends, the broth became quickly clouded.

34. Miller and Urey experiment
Attempts to create life in the laboratory
Provide a mixture of gases similar to that in the early atmosphere
Provide water to simulate oceans or pools
Provide a source of energy

35. Chemical Synthesis- “Primordial Soup”
Electricity was passed through the apparatus
Amino Acids and hydrocarbons were synthesized

36. Hydrothermal Vents
this environment provides the necessary gases, energy, & a possible source of catalysts

37. Panspermia
Living organisms were “seeded” on Earth as “passengers” aboard comets & asteroids from other planets that did support life

38. How do these competing hypotheses demonstrate the scientific process?
The strength or usefulness of a scientific claim is evaluated through scientific argumentation
Depends on
critical and logical thinking
active consideration of alternative scientific explanations to explain the data presented
It is a STRENGTH in science to have competing explanations from scientists
They are a source of new, testable ideas that have the potential to add new evidence to support one or another of the explanations