Aim: How did life on earth begin?

How is life able to exist today?????

I. Heterotroph Hypothesis

A. Autotroph - An organism capable of synthesizing its own food from inorganic substances, using light or chemical energy. Green plants, algae, and certain bacteria are autotrophs.

1. Carry out photosynthesis

6CO2 + 12H2O + sunlight ---> 6O 2 + C6 H12O 6 + 6H2 O or...carbon dioxide + water + sunlight ---> oxygen + carbohydrate + water

B. Heterotroph - An organism that cannot synthesize its own food and is dependent upon complex organic substances for nutrition. Animals are heterotrophs.

1. Carry out respiration

1 glucose + 6 oxygen = 6 carbon dioxide + 6 water + energy

C6H12O6 + 6O2 6CO2 + 6H2O + energy

respiration - process by which an organism exchanges gases with its environment.

C = Carbon

H = Hydrogen

O = Oxygen

N = Nitrogen

C6H12O6 = Glucose

Subscript indicates how many molecules of the particular element are present.

CO2 = Carbon Dioxide

H2O = Water

O2 = Oxygen

6CO2 + 12H2O + sunlight 6O 2 + C6 H12O 6 + 6H2 O

ReactantsYields

Products

C6H12O6 + 6O2 6CO2 + 6H2O + energy

Photosynthesis

Respiration

C. Early Earth Atmosphere

1. The early Earth atmosphere contained mostly hydrogen, water, ammonia, and methane.

2. Stanley Miller and Harold Urey recreated early Earth.

a. They filled a flask with hydrogen, methane, ammonia and water to represent the atmosphere.

b. They passed electric sparks through the mixture to simulate lightning.

c. The result: several amino acids (building blocks of proteins) began to accumulate.

Over time, the molecules became more complex and began to collaborate to run metabolic processes. Eventually, the first cells came into being. These cells were heterotrophs, which could not produce their own food and instead fed on the organic material from the primordial soup.

Heterotroph cells

Anaerobic cells – do not need oxygen to create energy

Release CO2 into atmosphere

Photosynthetic autotrophs

Release oxygen into atmosphere

Aerobic heterotrophs (anaerobic organisms die)