Geologic Time

1. Geologic Time Life and Geologic Time Chapter 6---Section 1

2. Geologic Time Scale • Division of Earth’s history into time units based largely on the types of life-forms that lived only during certain time periods • Four major subdivisions: • Eons (largest) • Eras • Periods • Epochs (smallest)

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4. The geologic time scale takes us all the way back from present day • Phanerozoic Eon • Cenozoic Era • Quaternary Period • Holocene Epoch to the origin of Earth 4.5 billion years ago during the • Hadean Eon (Precambrian Time)

5. Evolution • The process of change that occurs over time

6. Lamarck’s Theory of Evolution • Organisms pass on characteristics that they acquired during their lifetimes to their offspring • Ex: He thought giraffes necks got longer after a lifetime of eating foliage that was very high up in trees. Each succeeding generation would have a longer neck. • Was his theory correct?

7. NO!!!! • Think: Does a mouse that had its tail chopped off have a baby mouse with no tail?

8. Charles Darwin • Famous biologist who wrote a book called The Origin of Species in 1859 • Based on what he learned during his travels to the Galapagos Islands while traveling aboard the HMS Beagle in the 1830s

9. Darwin’s Theory of Evolution by Natural Selection • Main points: • Overproduction - most organisms produce more offspring than can be supported by the environment…not all of them can survive • Variation - there are many variations within a species…those who possess the most favorable ones have a better chance of survival

10. Natural Selection - Organisms with more favorable variations will live longer and, thus, have more opportunities to reproduce • Change Over Time - If organisms with favorable traits reproduce more than others, then these traits will be passed on more to future generations. If enough changes occur in a group, a new species may develop

11. Natural Selection • The process by which organisms best suited to the environment survive and reproduce • Also known as “survival of the fittest”

12. Modern Day Example of Evolution by Natural Selection • Peppered Moth - light-colored in countryside where no pollution, but dark-colored in industrial cities where there is a lot of dark soot from pollution on tree trunks • Light moths have a better chance of surviving and passing on their white genes in the countryside • Dark moths have a better chance of surviving and passing on their dark genes in the city

14. Trilobites • Organisms with a three-lobed exoskeleton • Lived in the ocean during the Paleozoic • Are considered to be index fossils • Different kinds of trilobites lived during different periods. All the different types show how trilobites evolved in response to changes in the environment.

15. Species • A group of organisms that normally reproduces only with other members of their group and whose offspring are fertile

16. Artificial Selection • Humans use artificial selection when breeding domestic animals. • By carefully breeding individuals with desired characteristics, animal breeders have created many breeds of cats, dogs, cattle, chicken, etc.

18. What drives evolution? • A response to major changes in: • Type of environment • Climate • Caused by Earth processes or dramatic life-changing events • Organisms are left with two choices: • adapt or become extinct!

19. Early Earth History Chapter 6---Section 2

20. Precambrian Time • Longest part of Earth’s history (90%) • Hadean, Archean, Proterozoic Eons • 4.5 billion to 544 million years ago • Life-forms: • Cyanobacteria • Invertebrates • Ediacaran Fauna

21. May be the longest time period, but relatively little is known about the organisms that lived then • Buried so deeply that they have been changed by heat and pressure • Have long since eroded • Most organisms didn’t have hard parts

22. Cyanobacteria • Blue-green algae thought to be one of the oldest life-forms on Earth • Colonies formed layered mats called stromatolites • Contained chlorophyll and used photosynthesis • Produced the first oxygen for Earth’s atmosphere

23. Invertebrates • Animals without backbones that appeared toward the end of the Precambrian • Not often preserved as fossils because of their soft bodies • Most evidence of their existence comes in the form of trace fossils

24. Ediacaran Fauna • Group of very unusual animals with shapes similar to modern jellyfish, worms, and soft corals that arose late in Precambrian Time • First found in Ediacara Hills in Australia • Bottom dwellers • Might have had tough outer coverings like air mattresses • Trilobites might have outcompeted them and caused their extinction, but nobody knows for sure

25. Paleozoic Era • 544 million to 248 million years ago • Traces of life are much easier to find in Paleozoic rocks because organisms with hard parts, such as shells, started to become common

26. Warm, shallow seas covered large parts of continents, so there are many marine fossils • i.e. trilobites • Life-forms: • Vertebrates • Amphibians • Reptiles

27. Vertebrates • Animals with backbones • First ones were fishlike creatures without jaws • Armored fish with jaws appeared during the Devonian • Some were large enough to eat sharks!

28. Life on Land • Many ancient fish had lungs as well as gills • Enabled fish to live in water with low oxygen levels because they could swim to the surface and breathe • Similar creatures are alive today that can get their oxygen from both water and air

29. Some had lungs and leglike fins, which they used to swim and crawl around on the bottom • Amphibians may have evolved from them • Still had to lay eggs in moist places

30. Then, some amphibians evolved an egg with a membrane that protected it from drying out, meaning it could be laid on land • These were the first reptiles • Had skin with hard scales that prevented the loss of bodily fluids • Now they could live far from water

31. Extinction • At the end of the Paleozoic Era (Permian Period), more than 90% of all marine species and 70% of all land species went extinct • Might have been caused by changes in climate and lowering of sea level caused by the formation of Pangaea • Might have been caused by extremely high level of volcanic activity

32. Might have been caused by an asteroid or comet impact • Perhaps it was a combination of all these factors

33. Mountain Building • Several mountain-building episodes occurred during the Paleozoic Era. • This is when the Appalachian Mountains formed.

34. Middle and Recent Earth History Chapter 6---Section 3

35. Mesozoic Era • 248 million to 65 million years ago • Pangea started to break apart during the Mesozoic Era. • Life-forms: • Dinosaurs • Birds • Mammals • Gymnosperms • Angiosperms

36. Dinosaurs • First small dinosaurs appeared during the Triassic Period • Larger species, like the Tyrannosaurus and Apatosaurus appeared during the Jurassic and Cretaceous • Dinosaurs were active • Gallimimus could run up to 65 mph! • Some may have been warm-blooded

37. Some dinosaurs nurtured their young and traveled in herds in which adults cared for their young. • Ex. Maiasaura

38. Birds • First appeared during the Jurassic Period • Some paleontologists think birds evolved from small, meat-eating dinosaurs. • The earliest known bird fossil is Archeopteryx. • Not a direct ancestor of modern birds

39. Mammals • Warm-blooded vertebrates that have hair covering their bodies. Females produce milk to feed their young. • First appeared during the Triassic Period • Earliest mammals were small, mouselike creatures

40. Gymnosperms • Plants that produce seeds, but no flowers • Ex: pine and ginkgo trees • First appeared during the Paleozoic and dominated for the majority of the Mesozoic

41. Angiosperms • Flowering plants that produce seeds with hard outer coverings • Ex: magnolia and oak trees • First evolved during the Cretaceous Period • Because their seeds are enclosed and protected, they can live in many environments • Angiosperms are the most diverse and abundant land plants today.

42. Extinction • The Mesozoic Era ended when many groups of animals, including the dinosaurs, disappeared suddenly. • Probably caused by an asteroid impact that sent up a huge cloud of dust and smoke, which blocked out sunlight causing many plants to die. All the animals that depended on these plants also died.

43. Cenozoic Era • 65 million years ago to present • The climate became much colder and ice ages occurred. • All the organisms that are alive today are descendants of survivors of the last mass extinction. • Mammals continued to evolve and became dominant.

44. Mammals • Many kinds of mammals became larger • Ex: horses • Not all mammals remained on land • Ex: ancestors of present-day whales and mammals evolved to live in the sea • Many species became isolated and evolved separately from other life-forms • Ex: marsupials in S. America and Australia • Homo sapiens evolved around 140,000 years ago.

45. Mountain Building • Many mountain ranges formed during the Cenozoic Era. • Alps in Europe • Andes in S. America • Himalayas in Asia