1. Evolution Evidence and Theory
Chapter 15
Lab Biology

2. A genetic change within a population over time!
Evolution
A genetic change within a population over time!
Population- interbreeding single-species group

3. Fossils Fossil - trace of a long-dead organism.
Sedimentary rock - formed by dust, sand, or mud deposited by wind or water over dead organism
Formed by hard body parts of an organism—shell, bones, teeth, or woody stems
Hard minerals replace the tissue of the organism leaving rocklike structures

4. Sedimentary Rock

5. Continue Fossils 2. mold – imprint in rock in the shape of an organsim
- limestone
3. cast – forms when molds are filled with hard minerals

6. Limestone Limestone – most abundant , non-classic sedimentary rocks.
Limestone is produced from the mineral calcite (calcium carbonate) and sediment.
Chalk is another type of limestone that is made up of very small single-celled organisms.

7. Cast !

8. Robert Hooke
He concluded that fossils are remains of plants and animals
He mostly studied “petrified wood” with the aid of the microscope
He hypothesized that living organisms had somehow been turned to rock

9. Petrified Wood Wood that has turned to stone!

10. Distribution of Fossils
Nicolaus Steno ( )
“law of superpositon” – states that the top layers of stratum contain the youngest fossils while the lower ones are older
This technique helps scientists to determine the “relative age” of a fossil
“absolute age”- age in years determined by radiological evidence

11. Succession of Forms
Mass extinctions – brief periods during which large numbers of species disappears.
Some of these life forms were unlike any organisms alive today
Probably resulted from drastic changes in the environment, volcanic activity or collisions with asteroids (may have blocked sunlight for long periods of time and decreased temp.)

12. Biogeography
Biogeography – is the study of the geographical distribution of fossils and of living organisms.
A comparison of fossil types with types of living organisms in the same geographic area
shows that new organisms arise in areas where similar forms already lived.
Ex: armadillos in North & South America where glyptodonts lived in the past.

13. Armadillos

14. Glyptodonts

15. Scaphognathus crassirostris Lab Fossil

16. Theories of Evolution
I. Lamarck’s Explanation:
He hypothesized that acquired traits were passed on to offspring.
Proposed that similar species descended from a common ancestor (fossil records)

17. Acquired Trait It’s not determined by genes!
Occurs during an organism’s lifetime
result of the organism’s experience or behavior.
Ex: 1. Muscles on a body builder
2. Giraffe’s necks did not get longer by trying harder and harder to reach tall trees- Genetic

18. Beginning of Modern Evolutionary Theory
II. Charles Darwin ( ) & Alfred Wallace ( )
Darwin & Wallace announced their hypotheses at the same time
Darwin’s name became more associated with evolution The Origin of Species published

19. Darwin’s Voyage on the Beagle
Sailed in 1831 for five years
Collected specimens and kept careful records of his observations
Sailed to South America (Galapagos Islands) and the South Pacific

20. Voyage of the Beagle

21. Darwin’s Findings
Collected 13 similar but separate species of finches.
Each finch species had a distinctive bill for specialized food source.
Implied that the finches shared a recent common ancestor

22. Darwin’s Finches

23. Darwin’s Findings

24. Darwin’s Theories TWO THEORIES;
1. DESCENT WITH MODIFICATION – The newer forms appearing in the fossil record are actually the modified descendants of older species
Organisms similar to each other- common ancestor
Organisms that are dissimilar -share a more remote ancestor

25. Continue…
2. MODIFICATION BY NATURAL SELECTION – states HOW evolution occurs.
Organisms best suited to their environment reproduces more successfully than other organisms

26. Adaptation- Adaptive advantage
A population of organisms adapt to their environment
# of genes for favorable traits increases
Fitness- a single genetic organism’s contribution to the next generation’s survival
A well adapted organism will reproduce successfully and have a high fitness

27. High Fitness? Low Fitness?

28. High Fitness? Low Fitness?

29. High Fitness? Low Fitness?

30. High Fitness? Low Fitness?