origins of life

life from random reactions

How did life begin? In order to answer this question, scientists need to know what kinds of materials were available at that time. We know that the ingredients for life were present at the beginning of Earths history. Scientists believe early Earth did not contain oxygen gas (photosynthesis had yet to evolve), but did contain other gases, including: nitrogen gas, carbon dioxide, carbon monoxide, water vapor, hydrogen sulfide. Some of the oldest fossils on Earth were found along the coast of Australia, similar to the area shown here. Where did these ingredients come from? Some chemicals were in water and volcanic gases ( Figure 1.2). Other chemicals would have come from meteorites in space. Energy to drive chemical reactions was provided by volcanic eruptions and lightning. Today, we have evidence that life on Earth came from random reactions between chem- ical compounds, which formed molecules, or groups of atoms bonded together. Small molecules, such as those present in the early atmosphere, can provide the components (including the elements C, H, N, O and S) to make larger molecules. These early molecules further reacted and eventually formed even larger molecules and organic compounds, such as amino acids (which combine to form proteins), and nucleotides (which form nucleic acids - RNA or DNA). These organic molecules eventually came together in the right combinations to form basic cells. The components that were necessary for the formation of the first cells are still being studied. How long did it take to develop the first life forms? As much as 1 billion years. Many scientists still study the origin of the first life forms because there are many questions left unanswered, such as, "Did proteins or nucleic acids develop first?" or "What exactly were early Earths atmospheric conditions like?" There is a lot of work still left to answer these and similar questions. Some clues to the origins of life on Earth come from studying the early life forms that developed in hot springs, such as the Grand Prismatic Spring at Yellowstone National Park. This spring is approxi- mately 250 feet deep and 300 feet wide.

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origin of life

There is good evidence that life has probably existed on Earth for most of Earths history. Fossils of blue-green algae found in Australia are the oldest fossils of life forms on Earth. They are at least 3.5 billion years old ( Figure 1.1).

instructional diagrams

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questions

early earth was full of gas like oxygen and carbon dioxide.

a. true

-->  b. false

organic compounds are needed to build cells.

-->  a. true

b. false

which of the following was not present in early earth?

a) nitrogen gas

b) carbon dioxide

c) water vapor

-->  d) hydrogen sulfoxide

chemical reactions need energy. where did this energy come from?

-->  a) volcanic eruptions and lightning

b) volcanic eruptions and nuclear fusion

c) lightening and thunder

d) thunder and volcanic eruptions

what is needed to build proteins?

-->  a) amino acids

b) nucleotides

c) organic compounds

d) all of the above

how old is the earliest forms of life?

a) at least 350,000 years old

b) at least 3.5 million years old

-->  c) at least 3.5 billion years old

d) over 5 billion years

where did these ingredients for early molecules come from?

a) water vapor

b) meteorites

c) volcanic gases

-->  d) all of the above

diagram questions

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