Download Section 3.1 The origins of life Q1. Bk Ch3 S3.1 Q1 Describe the

Section 3.1 The origins of life
Q1.
Bk Ch3 S3.1 Q1
Describe the conditions on the early Earth, and the types of chemicals that probably occurred there.
A1.
Bk Ch3 S3.1 A1
The early Earth probably had large expanses of ocean with only relatively small landmasses. The
atmosphere contained water vapour, hydrogen, hydrogen cyanide, carbon dioxide, nitrogen, and
possibly ammonia and methane but no oxygen and no ozone. Violent electrical storms were
commonplace and volcanic activity produced large amounts of gases, ash, dust and heat.
Q2.
Bk Ch3 S3.1 Q2
Define the term ‘evolution’.
A2.
Bk Ch3 S3.1 A2
Evolution means the changing of life-forms over time.
Q3.
Bk Ch3 S3.1 Q3
Why is it possible that there are other forms of life in the universe?
A3.
Bk Ch3 S3.1 A3
Carbonaceous chondrites are meteorites that have been found to contain organic molecules including
amino acids. The meteorites originated from outer space, which suggests that organic molecules also
exist in other parts of the universe.
Q4.
Bk Ch3 S3.1 Q4
Outline two scientific theories that attempt to account for the appearance of organic compounds on
Earth.
A4.
Bk Ch3 S3.1 A4
Theory 1: Meteorites that already contained organic compounds fell to Earth from outer space.
Theory 2: Organic substances were formed on Earth through chemical reactions between existing
inorganic materials using energy available from ultraviolet radiation or electrical discharges from
lightning.
Q5.
Bk Ch3 S3.1 Q5
Describe Urey and Miller’s experiment, and explain the significance of their results.
A5.
Bk Ch3 S3.1 A5
Urey and Miller set up a closed system containing ammonia, hydrogen and methane and subjected the
chemicals to continuous powerful electrical discharges. After a week the contents of the closed
chamber contained a number of amino acids. The results of their experiment were significant because
they demonstrated that complex organic molecules can be produced from simple, inorganic molecules
by natural systems.
3.1 Origins of life QA
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Q6.
Bk Ch3 S3.1 Q6
Identify two technological advances that have had an impact on our knowledge of the origins of life,
and explain how they had such an impact.
A6.
Bk Ch3 S3.1 A6
More recent experiments have been successful in producing amino acids using carbon dioxide instead
of ammonia and methane together with ultraviolet radiation instead of electrical discharge. This is
important because such conditions are believed to more closely resemble those that prevailed on the
early Earth.
Experiments using organic molecules together with water or heat have also added to our
understanding of how cell membranes may have formed in early life-forms. For example, certain
complex organic molecules spontaneously form individual droplets when suspended in water. That is,
each droplet is characterised by a distinct boundary that separates the molecules inside the droplet from
the surrounding environment.
3.1 Origins of life QA
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