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BIOLOGY WORKSHEET
CHAPTER 17 HISTORY OF
LIFE ON EARTH - NOVAK
• Ws Ch17HistoryOfLife K1-12.doc
Chapter 12 Section 1
• How Did Life Begin
How long ago did the Earth
form? ___
• FOUR POINT FIVE BILLION
What did the water vapor
condense into? ___
• OCEANS
Scientist think life has
evolved over hundreds of
___ of years?
• MILLIONS
Evidence of
the age of the
Earth can be
found by
measuring the
age of ___.
• ROCKS
___ ___ is the estimation of
the age of an object by
measuring its content of
certain radioactive isotopes.
• RADIOMETRIC DATING
___ are unstable isotopes
that break down and give off
energy in the form of
charged particles called ___.
• RADIOISOTOPES AND RADIATION
What is this breakdown
called? ___
• RADIOACTIVE DECAY
___ ___ is the time it takes for
one half of a given amount of
a radioisotope to decay.
• HALF LIFE
• Half life from radioactive decay
By measuring
the proportions
of certain
radioisotopes
and their
products of
___, scientists
can compute
how many half
lives have
passed since a
rock was
formed.
• DECAY
The half life of uranium is
760 million years.
If the age of the earth is 4.2
billion years, then 4.2/.76 =
about 6 doublings or about 64
times as much uranium
existed on earth at creation as
exists now.
• Half life from radioactive decay
These chemical reactions
produced many different
simple ___ molecules.
• ORGANIC
Energized by the ___
and ___ heat, these
simple molecules
formed more
complex molecules
that eventually
became the building
blocks of the first
cells.
• SUN &
VOLCANIC
The hypothesis that many of
the organic molecules
necessary for life can be
made from molecules of ___
matter has been tested and
supported by results of lab
experiments.
• NONLIVING
In the 1920s A. I. Oparin and
J.B.S. Haldane suggest that
the early ___ contained large
amounts of organic
molecules.
• OCEANS
What did this hypothesis
become known as? ___
• PRIMORDIAL SOUP MODEL
They also hypothesized the
molecules formed
spontaneously in chemical
reactions activated by ___
radiation, ___ eruptions, and
___.
• SOLAR AND VOLCANIC AND
LIGHTNING
The early Earth’s
atmosphere lacked ___
making formation of organic
molecules possible.
• OXYGEN
Name four common
compounds in Earth’s early
atmosphere NOT including
water. ___ ___ ___ ___ ___
• NITROGEN GAS AND HYDROGEN
GAS AND AMMONIA AND
METHANE
In 1953, who tested the
primordial soup model? ___
• STANLEY MILLER AND HAROLD
UREY
According
to Figure 2,
Miller-Urey
heated ___
in a flask.
• WATER
29. According
to Figure 2,
Miller-Urey
they then
added water
vapor and
what other
gases to the
tubes? ___
___ ___ ___
___
• NITROGEN GAS AND HYDROGEN GAS AND
AMMONIA AND METHANE
According to
Figure 2, MillerUrey, after the
spark and the
vapors had been
condensed, what
did they find in the
beaker below?
• ORGANIC COMPOUNDS
These results support the
hypothesis that some basic
chemicals of ___ could have
formed ___ under conditions
like those in the experiment.
• LIFE AND SPONTANEOUSLY
Recent discoveries have
caused scientists to ___ the
Miller-Urey experiment.
• REEVALUATE
Four billion years ago, Earth
did not have a protective
layer of ___ gas.
• OZONE
Without ozone, ___ radiation
would have destroyed any
ammonia or methane in the
early atmosphere.
• ULTRAVIOLET
• KEY
36. If these
gases are
absent from
the MillerUrey
experiment,
___
biological
molecules
are NOT
made.
If the chemicals
needed to form
life were not in
the atmosphere
some scientists
argue that the
chemicals ere
produced within
ocean ___ or
ocean ___.
• BUBBLES AND VENTS
In 1986, geophysicist Louis
Lerman hypothesized the ___
model of chemical origins.
• BUBBLE
The bubbles
protected the
methane and
ammonia
needed to make
amino acids
from ___ ___.
• ULTRAVIOLET RADIATION
Next, the bubbles rose to the
surface and burst, releasing
simple ___ molecules into
the air.
• ORGANIC
Once in the wind, these
simple organic molecules
were exposed to ultraviolet
radiation which provided ___
for further reactions
• ENERGY
Scientists ___ about the
details of the process that
lead to the origin of life.
• DISAGREE
However, short
chains of ___
have been
made to form
on their own in
water.
• RNA
RNA is the
nucleic
acid that
does what?
_________
• HELPS CARRY OUT DNA’S
INSTRUCTIONS
In The 1980s,
Thomas Cech
hypothesized
that ___ was the
first selfreplicating
informationstorage
molecule.
• RNA
Certain lipids, when
combined with other
molecules, can form a tiny
droplet whose surface
resembles a ___ ___.
• CELL
MEMBRANE
Short chains of amino acids
can gather into tiny droplets
called ___.
• MICROSPHERES
Another type of
droplet, called a
___ is composed
of molecules of
different types,
including linked
amino acids and
sugars.
• COACERVATES
Why do scientists think
microspheres are
important? _________
• THEY MIGHT HAVE BEEN THE
FIRST STEP TOWARD CELLULAR
ORGANIZATION
Scientists disagree about
the origin of ___.
• HEREDITY
Many
scientists
agree that
doublestranded
DNA evolved
after ___.
• RNA
RNA “___”
catalyzed
the
assembly
of the
earliest
___.
• ENZYMES AND
PROTEINS
But
researchers
do not yet
understand
how DNA,
RNA and
hereditary
mechanisms
first ___.
• DEVELOPED
END of Chapter 12 Section 1