1. History of Life
Chapter 19

2. The Fossil Record 19.1
Any evidence of an organism that lived long ago and are now extinct
Most are formed in sedimentary rocks
Provides info about structure, environment and way of life

3. Types of Fossils
Imprint
Cast
Mold
Trace
Amber-preserved

4. How are fossils formed?

5. Dating Earth’s History

6. Relative Dating Uses the position of fossils in sediment layers
Oldest at the bottom layer, youngest on top, not actual age
Index fossil
an easily recognized and widespread fossil used to compare the relative ages of rocks, ex. trilobites

7. Radiometric Dating
Uses radioactive isotopes (atoms with unstable nuclei that break down or decay)
Half-life – the time required for half of the radioactive atoms in a sample to decay
Potassium 40, half-life = 1.3 billion years
Carbon 14, half-life = 5730 years

8. Geologic Time Scale

9. Geological Time Scale Based on both relative and absolute dating
Major divisions
Eons
Eras
Periods

10. Precambrian Era Starts 4.7 bya Life began
Accounts for 90 % of Earth’s history
Primitive prokaryote were the first forms of life

11. Paleozoic Era Mesozoic Era Cenozoic Era
Appearance of plants and animals including fishes, reptiles, amphibians and ferns
Mesozoic Era
Mammals and dinosaurs
Flowering plants
Cenozoic Era
Primates
Modern human (200,000 years ago)

12. Life on a changing planet
Physical forces
Geological forces (building mountains and moving whole continents) have altered habitats of living organisms throughout Earth’s history
Plate tectonic theory
Explains the movement of continents (3 cm/year)
Africa and South America separated by Atlantic Ocean

14. Biological forces
Actions of living organism have changed conditions in the land, water, and atmosphere of the Earth
Earth cooled as CO2 decreased; used by early photosynthetic organisms

15. Patterns and Processes of Evolution 19.2

16. What processes influence survival or extinction of species and clades?
Group of species that includes a common ancestor and all descendants of that ancestor, living or extinct.

17. The more varied the species (more diversity) in a particular clade are, the more likely the clade is to survive environmental change.

18. Patterns of Extinction
Background extinction
Slow steady process of natural selection
Mass extinction
An event during which many types of living things suddenly die out
Makes new habitats and resources available to organisms left after a major catastrophe

19. Rate of Evolution

20. Gradualism
Species originate through a slow and steady change of adaptations

21. Punctuated Equilibrium
Speciation experience long, stable periods interrupted by brief periods of rapid evolutionary change

22. Patterns of Macroevolution

23. Adaptive radiation
When a single species or a small group of species evolves over a relatively short time into several different forms that live in different ways.

24. Hawaiian honeycreepers

25. Convergent Evolution Distantly related organisms evolve similar traits
Unrelated species occupy similar environments in different parts of the world

27. Coevolution
Process by which two species evolve in response to changes in each other over time
Ex. Flowers and pollinators (birds, bees, etc.)

28. Earth’s Early History 19.3 About 4.5 billion years old
Formed from cosmic debris colliding
Earth cooled enough for solid rocks to form and water vapor to condense and fall as rain, produce oceans
Earth’s atmosphere was primarily composed of
Carbon dioxide, water vapor, nitrogen

29. Hypotheses on how life began

30. Stanley Miller and Harold Urey’s experiment
Produced 21 amino acids—building blocks of proteins.
Proved incorrect
Nonlife to life is a big leap!

31. Microspheres Proteinoid microspheres
Contain selective permeable membrane
Water passes through
Store and release energy
About 3.8 billion years ago

32. RNA and DNA
Hypothesized that RNA formed before DNA

33. Origin of eukaryotic cells

34. Endosymbiotic theory
Prokaryotes were the ancestors of eukaryotic organisms
Small prokaryotes began living inside the larger cells

35. Mitochodria Chloroplasts
evolved from endosymbiotic prokaryotes that are able to use oxygen to generate energy-rich ATP
Chloroplasts
Evolved from endosymbiotic prokaryotes had the ability to photosynthesize

36. Modern evidence Lynn Margulis (1960) Supported endosymbiotic theory
Mitochondria and chloroplasts have DNA similar to bacterial DNA
Both have ribosomes resembling those of bacteria
Reproduce by binary fission when cells containing them divide by mitosis