ORIGINS OF LIFE

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HISTORY OF THE SEARCH FOR A BEGINNING

Spontaneous Generation: Idea that life comes from non-living things. Lazzaro Spallanzani (1729)*Francesco Redi*John Needham**Were all contemporariesLouis Pasteur (1864)

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REDI’S EXPERIMENT

Proof that spontaneous generation did not work as Needham and others thought.

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What did Spallanzani do? Was skeptical of spontaneous generation.Was influenced by the work of Redi.

Redi said that animals didn’t just appear, that eggs

were laid that were too small to see.Noted that covering the flask prevented growth of bacteria in the gravy.

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Why was Needham Wrong?

What do you see is the problem with Needham’s set up? Why did he think that his work supported SG?

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PASTEUR’S EXPERIMENT

Experiment proved SG was wrong, led to a deeper understanding “germs”

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PASTEUR’S FLASK

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ANCIENT EARTH-4.6BYA

ANCIENT EARTH IN UPPER MICHIGAN?

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-Greenstone, a rock that contains microfossils can be found in the UP

-The fossils are prokaryotes (no nucleus)

EVIDENCE FOR ANCIENT LIFE WORLDWIDE

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WORLD OF THE PRECAMBRIAN

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EARTH’S ANCIENT ATMOSPHERE

WATER VAPOR (H20)

CARBON MONOXIDE (CO)

CARBON DIOXIDE (CO2)

HYDROGEN (H2)

NITROGEN(N2)

AMMONIA(NH3)

METHANE (CH4)

MILLER AND UREY EXPERIMENT

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-Tried to imitate Earth’s early atmosphere by mixing gases

-Simulated sun and lightning by electrical spark.

-Produced organic molecules, including some components of DNA, RNA

ORGANIC MOLECULES IN SPACE AND FROM BELOW

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HOW DO COMPLEX MOLECULES FORM?

Organic molecules collect together in the absence of oxygen to form short protein chains.

The molecules tend to form into “droplets”, these are coacervates, they are life-like but not alive.

RNA has chemical properties that lead us to believe it was formed first.

FIRST CELLS

Prokaryotes that are similar to bacteria.

Anaerobes, can live without oxygen.

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Photosynthesis-the Early Years

Organisms would need to learn how to get food.

Heterotrophs would need to get their own food (they can’t make their own).

Autotrophs, organisms that can carry out photosynthesis, would have been successful.

Early autotrophs would have used hydrogen sulfide instead of water.

Formed stromatolites

BANDED IRON FORMATION

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Evolution of Aerobic Metabolism

Started as Earth’s atmosphere developed more Oxygen because of photosynthesis.

Metabolism that uses oxygen.

Gives more energy per sugar molecule than aerobic methods.

Eukaryotic Revolution!1.4 to 1.6 BYACells that contain a nucleus.Have other organellesReproduce sexuallySexual reproduction is an advantage because it mixes the genes around in a better way.Would lead the way to multi-cellular organisms.

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What is an microbial mat?

Very thin layer of microbes and cyanobacteriaProvide clues to very early life on earth.Early example of photosynthesis.Grow in such a variety of places that scientists use them as a guide for the search for extraterrestrial life.

We study the past by using the present as a model!

Principle of uniformitarianism

Extremophiles

Microbial Mats

Microbial Mats

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Microbial Mats Continued

What are extremophiles?

Organisms that live in extreme conditions.

Severe cold, heat

High acid or Low acid (pH scale)

Extreme pressures

Used as clues to possible life forms in space.

Let’s look at Yellowstone National Park for an Example

Other Examples

Halophiles, Methanogens

Where can we look to study life similar to our ancient origins?

EXTREME LOCATIONS ON EARTH

USE THIS INFORMATION TO SEEK OUT LIFE IN OTHER LOCATIONS IN OUR SOLAR SYSTEM

OTHER SOLAR SYSTEMS TOO.

CALLED ASTROBIOLOGY

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