Evolution and the History of Evolution and the History of Life Life

Part 3Part 3MLKMLK

Fall 2005Fall 2005

M.ElizabethM.Elizabethwww.marric.us/teachingwww.marric.us/teaching

Chapter 9: The History of Life on EarthChapter 9: The History of Life on Earth

I. Chapter 9.1: Evidence of the PastA. FossilsB. The Age of Fossils

Relative DatingAbsolute Dating

C. The Geologic Time ScaleDivision of the Geologic Time ScaleMass Extinctions

D.The Changing EarthPangaeaDo the Continents MoveAdaptations in Slow Motion

FossilsFossils

• Fossils are traces or imprints of living things. Fossils are found most often found in _____________________. Sedimentary rocks

•So what is a rock.•The rock cycle describes how rocks are formed. But sometimes there area complications

3 types of rocks3 types of rocks3 types of rocks3 types of rocks

• Igneous Rock

• Sedimentary Rock

• Metamorphic Rock

Rocks are classified according to how they were formed.

is a sequence of events involving the formation, alteration, destruction, and reformation of rocks as a result of natural processes ...

Glossary of Geology, Bates & Jackson, AGI

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The Rock Cycle is…The Rock Cycle is…• A process in which rocks change

form from one type to another type. Any of the three classes of rock can be changed into any other class.

• Igneous Rock- Formed from cooled magma

• Sedimentary Rock- Formed from sediments compacted and cemented together

• Metamorphic Rock- formed by changes in heat and pressure

• Metamorphic Rock

The Rock Cycle Rock Cycle explains how RocksRocks and Natural Natural

ProcessesProcesses are related

weathering

melting

pres

sure

, hea

t

Sedimentary Metamorphic

Igneous

compaction, cementation

Types of RocksTypes of RocksTypes of RocksTypes of Rocks

Igneous RocksMetamorphic Rocks

Sedimentary Rocks

Igneous RocksIgneous RocksWhat are They?What are They?

Igneous RocksIgneous RocksWhat are They?What are They?

• Fire Rocks• Formed

underground by trapped, cooled magma

Intrusive• Formed above ground

when volcanoes erupt and magma cools

ExtrusiveExamples? Intrusive igneous ____________________Extrusive igneous _____________

Sierra Nevada GraniteHawaiian Lava

Catastrophic Event: Eruption of Mount Vesuvius, Catastrophic Event: Eruption of Mount Vesuvius, Italy, 79 ADItaly, 79 AD

Catastrophic Event: Eruption of Mount Vesuvius, Catastrophic Event: Eruption of Mount Vesuvius, Italy, 79 ADItaly, 79 AD

Effects: Mass human mortality in Pompeii and Herculaneum

Volcanic ashlayerexcavated ruins

.

Minerals make up rocks.

Natural compounds and elements combine to form minerals.

Elements combine to form the natural compounds.

Rocks make up the Earth.This is a hierarchy of

the elements of Geology

Atoms make up elements.

Well back to Dating FossilsWell back to Dating Fossils

The Age of FossilsThe Age of Fossils• Relative Dating

– the law of superposition.

• Absolute Dating– the law of radioactive decay

Relative DatingRelative Dating• Relative Dating: the law of

superposition. • Older rocks are on the bottom and newer

layers are on the top, unless there has been folding, faulting or uplift.

• This method of dating fossils or layers relative to each other is called relative dating.

• Exact ages cannot be determined with relative dating.

Examples of complications when Examples of complications when reading sedimentary rocksreading sedimentary rocks

Absolute DatingAbsolute Dating • Absolute Dating: the law of radioactive

decay. Atoms are made of neutrons, protons, and electrons.

• Isotopes are atoms of the same element but with different numbers of neutrons. Some isotopes are not stable – unstable isotopes – release energy by decaying radioactively.

• Each time an isotope decays it becomes another element that may or may not be stable. Eventually, a stable isotope will be formed.

Absolute DatingAbsolute Dating • Each isotope decays at a particular

rate. The time it takes for one-half of the unstable isotopes (parent isotopes) to decay (into daughter isotopes) is its half-life.

• By measuring the ratio of parent isotopes to daughter isotopes is how the age of rock and fossils in the rock can be determined. Remember the Geology lab$$

• Absolute dating is how exact ages can be determined.

Example problemsExample problems• Thorioum-232 has a half life of 14.1 billion

years. How much of an 8 mg sample will be unchanged after one half-life? _____. How much after two half-lives?_______. How much after three half-lives?_______. How much after four half-lives?________.

• Carbon-14, an isotope of carbon, has a half-life of 5780 years. How much of the original sample will be left after 11560 years?

• After 17190 years?

4 mg2 mg

1 mg0.5 mg

25% = 1/412.5%= 1/8

Geologic Time ScaleGeologic Time ScaleBecause

geologic time is soooo long a different type of calendar is used to describe geologic time – the geologic time scale.

Divisions in the Geologic Time Divisions in the Geologic Time ScaleScale

• Paleontologists have divided the time scale into large blocks of time called eras which are then subdivided into periods that can be subdivided again.

• Our four eras are (Papa Pete Makes Cake)

• Precambrian, Paleozoic, Mesozoic, and Cenozoic.

• Eras are characterized by the type of animal that dominated the Earth at the time.

Major Era CharacteristicsMajor Era Characteristics• Precambrian Era – all time up to 540 million

years ago (_____) – prokaryotic (without nucleus) and eukaryotic (with nucleus) single celled organisms.

• Paleozoic Era began 540 mya to 248 mya – plants and fishes. Included the largest mass extinction when 90 percent of marine organisms and 75 percent of terrestrial organisms became extinct.

• Mesozoic Era – 248 mya to 65 mya –dominated by dinosaurs and other reptiles, and birds until their mass extinction when the era ended. Age of the Reptiles.

• Cenozoic Era – 65 mya to now – dominated by mammals – Age of Mammals.

mya

Mass ExtinctionsMass Extinctions• When a species is extinct it does not reappear.• There have been five major extinctions in the

Earth’s history. These extinction events are called mass extinctions.

• There are many possible reasons for these mass extinctions, a possible explanation for the dinosaur extinction is a meteorite hit that caused a brief changes in climate or atmospheric composition - Catastrophic.

• It is thought that man’s activities may be the source of the rapid extinctions that are occurring today.

• Is this the sixth mass extinction?

Name of Extinction Episode

Percent of species lost

MYA Affected Species Hypotheses

Ordovician(Paleozoic)

85% 440mya

Marine speciesTropical areas are

hit hardest. No terrestrial

vertebrates have evolved yet

Glaciation, oxygen depletion

Devonian(Paleozoic)

83% 360mya

Marine speciesMany fish and

marine invertebrates die

out.

Meteor impact, volcanism, glaciation, oxygen depletion

Permian(Paleozoic Era ends)

95% 250mya

Trilobites and other marine

species, but some land plants,

amphibians, and reptiles

Greatest mass extinction ever. Volcanism, meteor impact, sea level change, global warming glaciations

Name of Extinction Episode

Percent species lost

MYA Affected Species

Hypotheses

Triassic(Dinosaurs and mammals had just recently evolved; both live through this extinction.)

80% 213mya

Mostly marine species,

some land animals

Global cooling, meteor impact, sea-level change, oxygen depletion

Cretaceous/ Tertiary

akaKT ExtinctionMesozoic Era

ends

76% 66mya

Affected both land

and marine species.Dinosaurs become extinct

Meteor impact, volcanism, continental drift, mammal competition.

65 million of years after this mass extinction, early humans evolve.

QuaternaryFindings from a United Nations Report of 1,100 scientists in 2002)

70% NOW + 30 years

Affected both land

and marine species.

Anthropogenic -Human caused effects such as pollution, over population, global warming, over fishing, and deforestation.

0102030405060708090

100

Perc

enta

ge o

f S

peci

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ost

Geologic Period

QuestionsQuestions1. Which hypotheses is the most

common over all the mass extinctions?

2. Which mass extinction is the greatest?

3. Which mass extinction is the least?

Meteor Impacts

Permian

Quaternary – What is occurring now due to human activities

4. After each mass extinction new species evolved, what is this process called?

5. Has the number of species on Earth remained the same or changed over the history of the Earth?

SPECIATION

The number of species on Earth has changed with speciation and extinctions occurring over Earth’s history

6. Extinction normally occurs at what rate?

7. If the scientists are correct and trends continue, should we worry about extinctions today? Why?

10-100 species per year – VERY SLOWLY

Losing 70% of all species would be one of the great mass extinctions of the planet and we are the cause. The conditions that cause the loss will also affect our ability to live as well.

We are not

alone

The Changing EarthThe Changing Earth

• Example of the results from a changing earth:– Marsupials – mammals that carry their young in

pouches are found in Australia almost exclusively, although there are some in South America and one in North America.

– Why is a question that requires careful thought not just a “because”.

– The answer that geophysicists have developed is called plate tectonics which explains why Australia is so different.

– Australia separated from the main landmass of the earth’s early beginning.

http://www.ucmp.berkeley.edu/mammal/marsupial/marsupial.html

Opossum

PangaeaPangaea• Pangaea is the name given to the Earth’s

early landmass by Alfred Wegner. • Wegener published his theory called

Continental Drift in his 1915 book, On the Origin of Continents and Oceans.

• In it he also proposed the existence of the supercontinent Pangaea, and named it (Pangaea means "all the land" in Greek).

• The evidence Wegener used included the shapes of continents, the fossils of plants and animals at coastal margins, and that there has been drastic changes in the climates of continents.

Do the Continents Move? • Plate Tectonics – the outer crust is

underlain by a semi-molten material that circulates and in doing so creates convection currents that move the overlying crustal plates.

Adaptations in Slow Motion• Tectonic plates move slowly, slowly

enough for adaptations to occur.

Converging/Diverging Converging/Diverging PlatesPlates

Glacial StriationsGlacial Striations• How to “track” a glacier………..

Striations help determine which direction the ice was flowing as it moved across an area.

http://nsidc.org/glaciers/gallery/grooves.html

Homo sapiensHomo sapiens• The modern species of humans, the

only extant species of the primate family Hominidae.

• Thought to have originated in Africa.• ETYMOLOGY:New Latin Hom sapi ns,

species name : Latin hom , man + Latin sapi ns, wise, rational, present participle of sapere, to be wise.

That’s All FolksThat’s All Folks

What is theWhat is the

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The Rock Cycle

BerylBe3Al2(Si6O18)

MineralsMineralsMineralsMineralsGypsum (Mg Ca Carbonate)

Sulfur

PyritePyritePyritePyrite

Fools Gold (FeS2)

Metamorphic Grade - FoliatedMetamorphic Grade - FoliatedMetamorphic Grade - FoliatedMetamorphic Grade - Foliated

MetamorphicMetamorphicMetamorphicMetamorphic