The Origin of Life PowerPoint Notes 3/03 Integrated Science 2 Redwood High School Name: Period: I. Early Theories

A. -The hypothesis that life arises regularly from

things.

II. Experiments That Helped to Disprove Early Theories

A. Italian scientist, (1730’s)

1. Hypothesis: arose from tiny, non-viable eggs laid on meat

2. Procedures:

a) Put pieces of meat in several jars,

b) Cover the other half with thin gauze to

3. Results:

a) After a few days, meat in all jars spoiled and were found

only on the meat in the

B. French scientist, (1864)

1. Hypothesis: Microorganisms arise from nutrient broth

2. Procedures:

a) Place nutrient broth in a flask with a (this

permitted to enter, but trapped and other particles)

b) Boil the flask thoroughly to kill any

c) Do NOT the open end of the flask

d) Wait an before gathering results

3. Results:

a) After a year, could

be found in the broth!

b) Pasteur then the curved neck,

permitting dust and other particles to enter.

In just , the flask contained

microorganisms!

c) Microorganisms had clearly entered the flask with the

dust particles

III. Current Theories

A. The Formation of Complex Molecules

1. Procedures: Scientists have simulated the gaseous conditions of Earth’s early atmosphere,

to simulate early sunlight and lightening

Origin Of Life PowerPoint Notes 2

2. Results

a) In a few days, a of molecules formed including (the

building blocks of proteins)

b) collections of these molecules in combination with water tend to gather together into tiny

B. The First True Cells

1. They were (lacked nucleus), (survived in absence of oxygen)

that resemble types of bacteria alive today.

2. (not DNA) stored the

C. The Evolution of Photosynthesis

1. Early heterotrophs fed on until the supply diminished

2. favored organisms that could harness energy from an outside source

and use it for food.

3. At some point, a primitive form of evolved using H2S instead of __

4. The first were commonplace 3.4 bya and grew in layered formations

called

IV. The Road to Modern Organisms

A. Oxygen and Life

1. Modern photosynthesis using H2O evolved bya

2. Oxygen was released into the atmosphere as a

3. Oxygen was to early anaerobic organisms and most

4. Organisms that could survive, , in an environment began

to proliferate.

B. Eukaryotes and the Origin of Complex Cells

1. Eukaryotic organisms with a , DNA and membrane-bound organelles

evolved between bya

2. Eukaryotic ancestors probably that performed specific

functions, later becoming and .

C. Sexual Reproduction and Multicellular Life

1. The origin of sexual reproduction rapidly increased the rate of

2. Genes and traits began and combining in ways they were not capable of

before

3. created new species under the influence of natural selection