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Miller and Urey

Experiments suggested how mixtures of the organic compounds necessary for life could have arisen from similar compounds present on a primitive Earth; tested hypothesis and produced 20 amino acids; MIller was first person to obtain indirect evidence that organic molecules could have formed on early earth


hypothesized that organic compounds formed in warm seas and energy from the sun or lightning allowed the compounds to form more complex molecules to form the first organism

Schleiden, Schwann, and Virchow

-Came up with the cell theory: all living things are made of one or more cells
-All cells come from pre- exsiting cells (Virchow)
-Cells are the basic unit of structure and function in living things

main features of cells

plasma membrane, nucleus or nucleoid, and cytoplasm

plasma membrane

bilayer, fluid, and mosaic


where reactions happen in the cell; mostly made up of water

Why are cells small?

the membrane must allow for sufficient and rapid exchange to support the cell contents

endosymbiotic theory

theory that eukaryotic cells formed from a symbiosis among several different prokaryotic organisms


saclike structures that store materials such as water, salts, proteins, and carbohydrates


small membrane sacs that specialize in moving products into, out of, and within a cell

Key differences between prokaryotes and eukaryotes

Prokaryotes: bacteria, small, simple, formed 3.5 billion years ago
Eukaryotes: plant and animal cells, large, complex. formed 1.5 billion years ago

Where did life originate?

in early Earth's warm shallow seas the early atmosphere yielded organic molecules which yielded protocells. "primordial soup"

When did life on Earth originate?

3.5 billion years ago

animal cells

1) lacks cell wall 2) lacks chloroplasts 3) lacks large central vacuole

plant cells

1) have cell wall 2) have chlorophyll/chloroplasts 3) large central vacuole

Prokaryotes roles

O2 in atmosphere; nitrogen fixing; decomposition and cycling on nutrients; critical for soil fertility; imp. mutualists

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