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Chapter 13 – Geologic Time

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1 Chapter 13 – Geologic Time
13.1 Evolution and Geologic Time

2 The geologic time scale is a record of Earth’s history that shows events, time units and ages.

3 2. It is subdivided into smaller
units based on: 1. The types of life-forms living at the time. 2. Geologic events occurring at the time.

4 3. Eras- largest – based on life-forms. Periods- divide eras – based on life-forms and geologic events. Epochs- divide periods- smallest amount of time.

5 4. Organic evolution – the change in life-forms through time.

6 5. Species- a group of organisms that normally reproduce only among themselves.

7 6. When 2 different species breed their offspring are unable to reproduce.
Tigon – male tiger + female lion Liger – male lion + female tiger Males are sterile in both species



10 Albert's Squirrel South Rim Grand Canyon Kaibab Squirrel North Rim Grand Canyon

11 7. Natural selection – organisms with traits that are suited to a certain environment have a better chance of surviving to reproduce. First proposed by Charles Darwin in 1836.

12 8. The main cause of evolution of new species is
1. changes to environments 2. competition with others for resources

13 9. The Earth process most responsible for changing environments is
plate tectonics.

14 10. Endangered – when only a small number of members are living.
11. Extinct – when none of its members are living.

15 12. 3 ways humans contribute to extinctions.
1. destruction of habitat 2. competition for same food supply 3. overhunting

16 Precambrian - Longest geologic time unit in Earth’s history.
Began: 4600mya (4.6bya) Ended: 570mya

17 2. Precambrian fossils are sparse because:
Rocks are deeply buried or eroded away. Rocks have been changed by heat and pressure. Early organisms were soft-bodied – no hard parts.



20 3. Cyanobacteria – bacteria + algae. They photosynthesize
3. Cyanobacteria – bacteria + algae. They photosynthesize. Form stromatolites. Appeared: 3.5 billion years ago Take in: CO2 Release: O2



23 4. Cyanobacteria were important because: They changed Earth’s atmosphere by adding free O2 to the air. The ozone layer formed protecting organisms from UV rays. Single-celled organisms evolved into complex organisms.

24 Invertebrate- animal without a backbone.
Appeared: near the end of the Precambrian. Ex: jellyfish, sponges, worms





29 Evolutionary advancement that marked the beginning of the Paleozoic:
when organisms developed hard parts.


31 Paleozoic – “ancient life”.
Life-forms that were most abundant during the Paleozoic- ocean dwelling (marine ) organisms. Why? Warm, shallow seas covered most of the Earth. Ex: trilobites, brachiopods, cephalopods, crinoids.







38 Vertebrate – animals with a backbone.
Appeared: Ordovician Period Ex: jawless fishes, bony fishes, reptiles, mammals




42 10. Amphibian – vertebrates that live on land but must return to water to reproduce (lay eggs).
Appeared: Devonian Period Ex: frogs, salamanders


44 11. Reptiles – vertebrates that live entirely on land – eggs have a leathery or mineralized covering. Appeared: Late Carboniferous (Pennsylvanian Period) Ex: tortoises, snakes, lizards, crocodiles.



47 12. Appalachian Mountains formed at the end of the Paleozoic.
13.What marked the end of the Paleozoic? Largest mass extinction in Earth’s history. Formation of Pangaea.

48 Mesozoic – “Middle Life” aka – “Age of Dinosaurs”

49 All continents are still together as Pangaea

50 3. Laurasia – North America, Europe, Asia, Greenland

51 3. Gondwanaland – South America, Africa, Antarctica, India, Australia

52 Small dinosaurs first appeared in the Triassic Period.
Sellosaurus Coelophysis

53 5. Evidence that dinosaurs were warm-blooded:
Tracks indicate they were fast- moving. 2. They traveled in herds and nurtured their young. 3. Bone structure resembles warm-blooded animals.

54 6. Birds first appear in the Jurassic Period

55 7. Archaeopteryx had wings and feathers like a bird, but teeth, claws and a tail like a dinosaur.

56 8. Mammals first appeared in the Triassic Period.

57 9. Traits allowing mammals to survive:
1. Hair or fur covering their bodies.

58 2. They are warm-blooded. 3. Produce milk to feed their young.

59 10. Gymnosperms – "naked seed plant", no fruit covering their seeds.

60 First appeared: Devonian Period
Ex: ferns, palms, ginkgos, pines

61 11. Angiosperms – flowering plants
11. Angiosperms – flowering plants. Produce seeds with a hard outer covering and/or fruit. First appeared: Early Cretaceous Period

62 Ex: fruits, vegetables, flowers, flowering trees

63 11. The end of the Mesozoic Era was marked by:
Break-up of Pangaea, seas drained from lands, extensive volcanism, extinction of dinosaurs.

64 12. Cenozoic – "Recent Life" aka "Age of Mammals"

65 13. The Alps in Europe form from collision between African and Eurasian plates.

66 14. The Himalaya Mountains formed from the collision between the Indian and Eurasian plates.

67 15. Placental mammals – nourish their young internally from a placenta
15. Placental mammals – nourish their young internally from a placenta. Offspring born live & independent. First appeared: Cretaceous Period




71 Ex: rodents, bats, dogs, cats, cows, humans

72 16. Marsupials – offspring are born immature – must complete development in a pouch.
First appeared: Cretaceous Period

73 Ex: kangaroo, koala, wombat, opossum

74 The size of a Koala just after birth, crawling to the pouch.
17. Australia has the greatest number of marsupials. The size of a Koala just after birth, crawling to the pouch.

75 Monotremes – egg-laying mammals

76 18. Homo sapiens first appeared about 500,000 years ago.
Homo sapiens neanderthalensis appeared about 250,000 years ago. Homo sapiens sapiens appeared about 100,000 years ago. We see the emergence of specifically human activities, such as art and religion.

77 19. Humans have been the dominant life form for the past 10,000 years.
Starting about 10,000 years ago, agriculture, the domestication of animals, cities, and writing soon followed.

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