1. Chapter 14: Geological Time

2. Aim: How do we divide geologic time?

3. Geological Time Scale
Paleontologists have divided Earth’s history into time units based on the life-forms that lived during certain periods
4 Major subdivisions:
Eons
Longest subdivison
Based upon abundance of certain fossils

4. Eras
2nd longest subdivision
Marked by worldwide change in types of fossils present
Ex: Mesozoic Era-many invertebrates became extinct
Periods
Characterized by the types of life existing worldwide
Epochs
Smaller than periods
Characterized by differences in life forms

5. Aim: How does evolution relate to the divisions of the geologic time scale?

6. Organic Evolution Species have changed over geologic time
Environmental changes can affect an organism’s survival
Those that don’t adapt to changes are less likely to survive
Species- group of organism that normally reproduce only with other members of their group
Offspring of 2 different species can not reproduce (sterile)

7. Natural Selection Charles Darwin proposed this theory
Sailed around the world gathering information
Is a process by which organisms with characteristics that are suited to a certain environment have a better chance of surviving and reproducing than organisms that do not have these characteristics
Organisms compete with each other for resources (food and living space)
Organisms in the same species can show variations-could help or hurt the organism’s chance of surviving

8. Organisms poorly adapted to environment-produced few or no offspring
Organisms suited for their environment-lived longer and better chance of producing offspring
Organisms poorly adapted to environment-produced few or no offspring
A new characteristic becomes common in a species only if:
some members already possess that characteristic
That trait increases the animal’s chance of survival

9. Aim: How do trilobites help explain evolution?

10. Trilobites Structure of the hard outer skeleton or exoskeleton
3 lobes that run the length of the body
Body made up of
Head-cephalon
Segmented middle-thorax
Tail-pygidium
Figure 7-Pg 397

11. Lived in Earth’s oceans for more than 200 million years
During Paleozoic Era, some species of trilobites became extinct and new ones evolved
Showed different characteristics during the different periods of the era
Trilobite eyes-changed over time, tell us about where they lived
Trilobite bodies-changed over time too
Olenellus had an extremely segmented body compared to other trilobites, thought to be primitive

12. Aim: How has Plate Tectonics affected species?

13. Plate Tectonics
Earth’s moving plates caused continents to collide and separate many times
Collisions caused mountains and closed seas
Pangaea-supercontinent when the continents came together (end of Paleozoic Era)
Separation of continents caused wider and deeper seas
trilobites lived in oceans and their environment changed or was destroyed
Only one explanation of the extinction of trilobites

14. Aim: What was life like during the Precambrian Time?

15. Precambrian Time Longest part of Earth’s history
Includes the Hadean, Archean and Proterozoic Eons
Lasted from 4.5 billions years ago to 544 million years ago
Little is known about this time because rocks have been so deeply buried they have been changed by heat and pressure
Many fossils can’t stand these conditions

16. Earth was a lifeless planet with many volcanoes
Stromatolites-layered mats formed by cyanobacteria
Cyanobacteria-blue green algae; one of the earliest life forms on Earth
First appeared 3.5 billion years ago
Contain chlorophyll
Used photosynthesis
Produced O2 which helped change Earth’s atmosphere
O2 became a major atmospheric gas
Ozone layer began to form

17. Invertebrates appeared toward the end of Precambrian time
The production of O2 made it possible for single-celled organisms to evolve into more complex organisms
Many of these fossils are trace fossils
Edicaran animals
Bottom dwellers
Might have had tough outer coverings
Looked like modern jellyfish, worms and soft corals

18. Aim: What was life like during the Paleozoic Era?

19. Paleozoic Era Organisms with hard parts mark the beginning of this era
Began about 544 million years ago
Ended 248 million years ago
Warm, shallow seas covered large parts of continents
Many life forms during this time were marine
Trilobites present
Fossils shows many animals had shells

20. Invertebrates not the only animals
Vertebrates evolved during this era
First vertebrates were armoured fish-had very powerful jaws
By the end of Devonian Period forests appeared and vertebrates adapted to land
Many ancient fish had lungs and gills-enabled fish to live in low O2 leveled water
Paleontologists believe amphibians evolved from panderichthys- leglike fins and lungs

21. By the Pennsylvanian Period reptiles evolved
Produced egg with a membrane that protected it from drying out-reproduction takes place away from water
Have skin with hard scale that prevent loss of body fluids
Many mountains formed during this era
Ex: Appalachian Mountains
Ocean separating North America from Europe and Africa closed
Collision of volcanic islands generated mountains
African plate collided with the North American plate

22. At the end of the era:
90% of all marine species died off
70% of all land species died off
Possible reasons are climate change and lowering of sea level
Pangaea formed closing seas and creating mountains
Organisms were unable to adapt to these changes
Volcanoes were very active
A large asteroid may have hit Earth

23. Aim: What were the characteristic life-forms during the Mesozoic Era?

24. Mesozoic Era Started 243 million years ago Ended 65 million years ago
Marked by rapid movement of Earth’s plates
All continents joined (Pangaea)
Separated into 2 large landmasses (Laurasia and Gondwanaland)
These 2 land masses continued to break apart into the present day continents

25. Reptiles became the largest group of animals on land by the Triassic period
First small dinosaurs appeared during Triassic period
Larger dinosaurs appeared during the Jurassic and Cretaceous periods
Fossils indicated some dinosaurs might have been warm-blooded and fast moving animals like present day mammals and birds

26. Birds appeared during the Jurassic period
Fossils indicated some dinosaurs nurtured their young and traveled in herds
Ex: Maiasaura
Birds appeared during the Jurassic period
Paleontologists believed birds evolved from small, meat-eating dinosaurs
Earliest bird-Archaeopteryx
Mammals first appeared in the Triassic period
Earliest mammals resembled today’s mouse
Warm-blooded vertebrates and produce milk to feed young
These 2 characteristics enables mammals to survive in many changing environments

27. Gymnosperms dominated the Mesozoic Era-are plants that produce seeds, but not flowers
Many are still around today
Angiosperms (flowering plants) first evolved during the Cretaceous Period
Can live in many environments
Most diverse and abundant land plants today
Ex: magnolia and oak trees

28. Ended with a major extinction of land and marine species
Dinosaurs disappeared
Scientists believe an asteroid or comet collided with Earth blocking out the sun
Plants and those organisms that depended on plants died out
The animals you see today and descendants of those who survived this mass extinction

29. Aim: What are the characteristics and life-forms of the Cenozoic Era?

30. Cenozoic Era Era of recent life Began 65 million years ago
Living in this era today
Many mountain ranges in North America, South America and Europe formed during the beginning of the era
Ice age occurred
Divided into 2 periods-Tertiary Period and Quaternary Period, which began 1.8million years ago

31. Alps in Europe formed
Andes in South America formed
Himalya formed while India moved northward and collided with Asia (highest mountain on Earth)

32. Many kinds of mammals became larger
As Australia and South America separated from Antarctica many species became isolated
Evolved separately from life-forms in other parts of the world
Evidence of this is marsupials
Homo sapiens appeared about 140,000 years ago
Appearance of humans could have led to the extinction of many other mammals