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EARTH’S EARLY HISTORY: The formation of the planet and the beginning of life

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Earth’s Early History:. The formation of the planet and the beginning of life. An Important Note:. - PowerPoint PPT Presentation

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Page 1: Earth’s Early History:

EARTH’S EARLY HISTORY:The formation of the planet and the beginning of life

Page 2: Earth’s Early History:

AN IMPORTANT NOTE: These large-scale hypotheses are based on

a relatively small amount of hard evidence. Because of this, these exciting inferences will without doubt develop, improve, and even change over time.

Page 3: Earth’s Early History:

HOW THE PLANET FORMED

Page 4: Earth’s Early History:

FORMATION OF PLANET EARTH 4.6 billion years

ago

Cosmic debris

Collisions, compression, decay…HEAT

Page 5: Earth’s Early History:

FORMATION OF PLANET EARTH Differentiation:

Iron sank

Less dense “floated” to form crust

Least dense = first atmosphere

Page 6: Earth’s Early History:

EARTH’S EARLY ATMOSPHERE Very different from today’s atmosphere:

Much hotter Frequent volcanic eruptions Little or no oxygen Toxic to us!

vs

Page 7: Earth’s Early History:

SETTING THE STAGE FOR LIFE 3.8 billion years ago, Earth cooled, water

in liquid form

Global ocean

Here, life will somehow form!

Page 8: Earth’s Early History:

ANIMATION

http://www.precisiongraphics.com/portfolio/animation/

Page 9: Earth’s Early History:

THE FIRST ORGANIC MOLECULESLife cannot begin without these!

Page 10: Earth’s Early History:

HOW DO WE GET LIFE?

Living things can come from non living things

All living things must come from a living thing

Spontaneous Generation Biogenesis

In the mid 1600’s Francesco Redi decided to find out…

Page 11: Earth’s Early History:

REDI’S EXPERIMENT: DO FLIES SPONTANEOUSLY GENERATE ON ROTTING MEAT?

Uncovered jars with rotting meat

Covered jars with rotting meat

Air could pass through but not flies

Control Group Experimental Group

Page 12: Earth’s Early History:

RESULTS: BIOGENESIS

Page 13: Earth’s Early History:

TWO MORE EXPERIMENTS…1700’SLazzaro Spallanzani: Tried to prove micro-

organisms did not come from a “vital force” in the air

Opponents said that he heated the flasks for too long removing the “vital force”

Page 14: Earth’s Early History:

FINALLY AN ANSWER…MID 1800’SLouis Pasteur Similar to Spallanzi’s

but allows for the air to continue to be exchanged with the outside

Curve prevents solids from passing into the flask

FINALLY Accept Biogenesis

Page 15: Earth’s Early History:

THE FIRST ORGANIC MOLECULES Could organic molecules have evolved under

the conditions of early Earth?

2 American chemists tried to answer that: Miller and Urey

Page 16: Earth’s Early History:

MILLER AND UREY EXPERIMENT Showed that

mixtures of organic compounds necessary for life can be created from simpler compounds that were present on early Earth

Page 17: Earth’s Early History:

IMPORTANT NOTE: Not accurate!

Corrected, showed that organic compounds CAN form under these conditions…even cytosine and uracil, two bases found in RNA!

Page 18: Earth’s Early History:

LIFE’S ORIGINS

Page 19: Earth’s Early History:

PROTEINOID MICROSPHERES Organic molecules forming bubbles

Selectively permeable membranes

Can store and release energy

Similar to modern cell

Page 20: Earth’s Early History:

RNA AND DNA RNA molecules can form

Theory: could these early forms of RNA (that predate more complex DNA and RNA molecules) have found a home inside a microsphere?

Page 21: Earth’s Early History:

OXYGEN

The fossil record photosynthetic bacteria

Rising levels of oxygen in atmosphere

The rise of oxygen drove some life forms to extinction (it was toxic to them), while other life forms were able to thrive

Page 22: Earth’s Early History:

THE BEGINNING OF MODERN LIFEEukaryotic Cell Origins

Page 23: Earth’s Early History:

ORIGIN OF EUKARYOTIC CELLS Prokaryotic cells

Internal membrane nucleus

Cells with a nucleus! The first eukaryotes!!!

Page 24: Earth’s Early History:

ORIGIN OF EUKARYOTIC CELLS Endosymbiotic Theory

Page 25: Earth’s Early History:

EVOLUTION OF MULTICELLULAR LIFEThrough 4 eras

Page 26: Earth’s Early History:

PRECAMBRIAN ERA 650-544 million years ago

Simple anaerobic life forms Photosynthetic life develops adding oxygen

to the atmosphere Eukaryotes appear

Life still only in the sea!

Page 27: Earth’s Early History:

PALEOZOIC ERA 544-245 million years ago

Diversity of marine life First vertebrates First organisms walked on land Plants and insects appeared Mass extinction – 95% of life dies out!

Page 28: Earth’s Early History:

MESOZOIC ERA 245-65 million years ago

Appearance of dinosaurs (which later dominate the land on Earth) Small mammals develop Leafy trees, shrubs, and flowering plants

develop Mass Extinction – 50% of life dies out

Page 29: Earth’s Early History:

CENOZOIC ERA 65 million years ago – present

Plants and insects thrive Mammals adapt to environment well and

dominate life on Earth Appearance of human ancestors Ice age

Page 30: Earth’s Early History:

BUT HOW DO WE KNOW THIS?Fossilization and Determining Ages

Page 31: Earth’s Early History:

FOSSILIZATION Fossil = remains or traces of an organism that

died long ago Ways to make a fossil

Sedimentary Rock Amber Volcanic Ash

Page 32: Earth’s Early History:

SEDIMENTARY ROCK – RELATIVE DATING

Principle of Superposition (1669) – if rock strata (layers) have not been disturbed, the lowest stratum was formed first

Relative Age – age compared to other fossils, determined by location in the strata

Page 33: Earth’s Early History:

RADIOMETRIC DATING Compare the

amount of a naturally occurring isotope to its decay products.

Absolute Age – age of the rock as determined by radiometric dating

Half Life – Time it takes for half of the material to decay