history of the earth chapter 14. formation of the earth

History of the Earth

Chapter 14

Formation of the Earth

Where does life come from?

Spontaneous generationthe belief that living things arise from nonliving things

Biogenesis all living things come from other living things

Redi’s experiments Spallanzani’s experiments

Pasteur’s experiments

Redi’s Experiment (1626-1697)

Italian physician and poet who demonstrated that the presence of maggots on rotting meat does not result from spontaneous generation but from eggs laid on the meat by flies.

Pg. 279

Spallanzani’s Experiments (1729-1799)

Italian naturalist whose experiments disproved that microorganisms spontaneously generated from meat broth in open flasks.

Pg. 280

Pasteur’s Experiment (1822-1895)

A French chemist who proved that microorganisms are carried by dust and not air.

Improved on Spallanzani’s experimentPg. 281

The First Organic Compounds

Alexander Oparin’s Hypothesis, 1920’s):

Thought that primitive atmosphere contained: NH3, H2, H20, and C-H compounds

At high temperatures, these gases might have formed simple organic compounds like amino acids

Oparin’s Theory Con’t

When the Earth cooled, the water vapor condensed into lakes and seas with the organic compounds within

With the help of lightning and UV radiation, these organic compounds reacted with each other forming macromolecules essential to life.

Can that REALLY happen?

Yes! According to experiments performed by Miller and Urey

Products of experimental synthesis:Amino acidsATPDNA nucleotides

Miller ExperimentMiller Experiment

Water Vapor Forms

Water Vapor Forms

Input Chamber

Input Chamber

CondenserCondenser

Spark Chamber

Spark Chamber

Attempts to Create LifeAttempts to Create Life

“It came from outer space!”

Some scientists hypothesize that organic compounds may have come from meteoroids from space

Microfossil Lab!

Earth’s Age

More than 4 BILLION years old!

How do scientists “know” this?Radiometric dating

Measurement of the decay of commonly occurring radioactive isotopes

Ex) Carbon dating

Fossils

The remains of ancient animals and plants

Found in every continent on earthFormed from sedimentary rockPaleontology- the branch of biology that

studies past forms of life (namely fossils!)

Ancient Bat Saber-Toothed Cat

The Fossil Record

From the 1830s onwards, geologists noted how fossils became more complex through time. The oldest rocks contained no fossils, then came simple sea creatures, then more complex ones like fishes, then came life on land, then reptiles, then mammals, and finally humans. Clearly, there was some kind of 'progress' going on.

The First Prokaryotes

About 3.5 bya the first prokaryotes,

cells without a true nucleus (like bacteria), came into existence.

The first cells were probably anaerobic and heterotrophic.

Resemble modern day Archaebacteria, which live in extreme enviornments

Rise of photosynthesis and aerobic respiration

Cyanobacteria- group of unicellular, autotrophic prokaryotes about 3 bya

Increased the level of atmospheric oxygen

The First Eukaryotes

Endosymbiosis- about 2.0 bya, a small aerobic prokaryote began to live inside a larger anaerobic prokaryote

aerobic prokaryotes evolved to modern mitochondria

Photosynthetic cyanobacteria evolved into chloroplasts

Endosymbiosis:

Extinction 65 mya

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