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
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
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
1) lacks cell wall 2) lacks chloroplasts 3) lacks large central vacuole
1) have cell wall 2) have chlorophyll/chloroplasts 3) large central vacuole
O2 in atmosphere; nitrogen fixing; decomposition and cycling on nutrients; critical for soil fertility; imp. mutualists