Homework 2 ASTBIO 115 2023
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Dec 6, 2023
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ASTBIO 115, AU 2023, HW2
Astrobiology: Life in the Universe
Name:
Lab Section:
Homework #2
50 points
Chapter 4
(30 pts)
1.
Describe the three basic types of rock and the rock cycle. What is a mineral? How do we
study rocks in the laboratory? (3pts)
Igneous, metamorphic, and sedimentary. Magma cools and crystals start forming creating
igneous rock. The elements erode and weather rocks into sediments, these sediments are
then deposited and compacted down and cemented together creating sedimentary rock. A
rock is exposed to high heat and temperature within the crust. However, the rock doesn’t
melt all the way it can have a new mineral composition or texture. A mineral is a solid
substance with a well-defined composition and a specific crystal structure. They use
optical microscopes to closely examine rocks and soil for mineral composition and grain
size.
2.
How old is the Earth? How do we know? (2pts)
Earth is estimated to be 4.5 billion years old, and we know this because of radiometric
dating.
3.
What evidence do we have for the operation of plate tectonics in Earth’s distant past?
Why do we think Earth has plate tectonics? (3pts)
We have evidence of plate tectonic movement from fossils, glaciers, and complementary
coastlines. We can compare one location to the next and see similarities pointing to
tectonic movement. As Earth’s mantle heated and cooled and broke the crust apart
creating continents and mountains which continues today.
4.
Briefly describe the mechanism by which the greenhouse effect warms a planet. What are
the most common greenhouse gasses? (3pts)
The sun sends out waves of energy and Earth’s atmosphere allows only certain ones
through and reflects the other ones back into space. The wavelengths that are let through
are trapped, heating up Earth. Carbon dioxide, methane, nitrous oxide, and various
synthetic chemicals are the most common greenhouse gases.
5.
Choose the best answer to each of the following. Explain your reasoning with two or
more complete sentences
. (3pts)
Earth’s oceans formed…
(a) During the late stages of accretion as water ice collected on the surface
(b) from water vapor outgassed by volcanoes
(c) when Earth underwent differentiation.
It is theorized that water came from ice in asteroids or that water was always present in Earth’s
mantle. As Earth was heating up water vapor was released and expelled through openings or
volcanoes.
6.
Choose the best answer to each of the following. Explain your reasoning with two or
more complete sentences
. (3pts)
Earth has retained a lot of internal heat primarily because of its…
(a) distance from the Sun
(b) large iron core
(c) relatively large size.
Combined with Earth’s atmosphere and its closeness to the sun, Earth can retain heat and stay at
a survivable temperature. The sun sends out wavelengths and some can penetrate the Earth’s
atmosphere which is then trapped heating up Earth.
7.
Choose the best answer to each of the following.Explain your reasoning with two or more
complete sentences
. (3pts)
Earth has far less atmospheric carbon dioxide than Venus because…
(a) Earth was born with less of this gas
(b) Earth’s carbon dioxide was lost in the giant impact that formed the
Moon
(c) Earth’s carbon dioxide is locked up in carbonate rocks.
Venus’s surface is so hot and dry that carbon bearing compounds that the carbon is evaporated
releasing it into the atmosphere. On the other hand, Earth isn’t hot enough for the carbon to
evaporate so it remains in the rocks.
8.
This is a short answer/short essay question. In 5-8 sentences react to the following
prompt: (5pts)
Suppose the giant impact that formed the Moon had never occurred. How would
you expect Earth to be different? Explain your reasoning carefully.
To begin with without the moon there would be no waves or tides in the ocean there would only
be solar tides, as a result there would be a different climate possibly even uninhabitable. It is
possible that Earth would be a different size, because it is believed that Earth gained some mass
from the Theia impact. The Earth would be darker at night because the moon reflects the sun
giving the night light, but we would be able to see more stars. Also Earth would probably be
colder because Theia gave Earth iron for Earth’s core which causes it to be warmer. Earth would
probably rotate on a perfect up and down axis.
9.
For this question, please show all calculations clearly
AND
state your final answers in
complete sentences
. (5pts)
“In daylight, Earth’s surface absorbs about 400 watts per square meter. All of
Earth’s internal radioactivity produces a total of 3 trillion watts, which leak out
through the surface. Calculate the internal heat flow (watts per square meter)
averaged over Earth’s surface. Compare this internal heat flow quantitatively to
solar heating, and comment on why internal heating drives geological activity.
30*10^13=4
πr^2
.06 watts per square meter
sun=~7000
Earth’s surface area is represented as 4πr^2, and we assume the radioactivity is
uniform across Earth. So the amount of energy per square meter is the total energy
produced divided by the Earth’s surface area. Therefore, .06 watts per squared
meter is given off of Earths crust.
Look up earth surface
5.1*10^8km^2
Chapter 5 (20 pts)
10. What are the three domains of life? Which domain do we belong to? (2pts)
Bacteria, Archaea, Eukarya and we belong to the Eukarya domain.
11. Briefly describe the six key properties that appear to be shared by most living organisms
on Earth. (3pts)
Order, homeostasis, growth and development, reproduction, energy utilization, response
to environment
12. Choose the best answer to each of the following. Explain your reasoning with two or
more complete sentences
. (4pts)
Natural selection is the name given to…
(a) the occasional mutations that occur in DNA
(b) the mechanism by which advantageous traits are preferentially passed
on from parents to offspring
(c) the idea that organisms can develop new characteristics during their
lives and then pass these to their offspring.
Natural selection and the evolution of advantageous characteristics happens over many
lifetimes. Species change from generation to generation adapting to their environment and
passing down traits that promote survival.
13. Why do we say that living cells are carbon-based? Briefly discuss whether life elsewhere
could be based on something besides carbon. (2pts)
Carbon is very abundant, and it forms stable bonds with several different elements. It also forms
polymers at temperatures commonly found on Earth. It is unlikely that life elsewhere would be
something other than carbon based because carbon is so compatible with different elements and
there aren’t any abundant elements that can form as many bonds as carbon can.
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14. Choose the best answer to each of the following. Explain your reasoning with two or
more complete sentences
. (4pts)
Generally speaking, an extremophile is an organism that…
(a) thrives in conditions that would be lethal to humans and other animals
(b) could potentially survive in space
(c) is extremely small compared to most life on Earth.
Extremophiles are capable of surviving in extreme environments that are unsuitable to all or
almost all other species. These organisms can be considered ecologically dominant. There have
been encased spores and bacteria that have been dormant or more than 40 million years, and
they continue to live and survive.
15. For this question, please show all calculations clearly
AND
state your final answers in
complete sentences (5pts)
“A typical eukaryotic cell, such as a cell in the human body, uses about 2 * 10^-
17 joule of energy each second. The breakdown of a single molecule of ATP (in
which a phosphate separates from ATP to make ADP; see Figure 5.13) releases
about 5 * 10^-20 joule of energy.
(a) About how many molecules of ATP must be broken down and reassembled
each second to keep a eukaryotic cell alive?
2*10^-17/5*10^-20=400 The amount
of energy a human cell uses divided by the breakdown of single molecule of ATP
equals the amount of ATP breakdown to keep a eukaryotic cell alive.
(b) How many times does this ATP recycling occur each day in a typical cell?
ATP recycles 3.46*10^7 each day in a typical cell.
(c) The human body has roughly 1014 cells. Approximately how many cycles of
the ATP reaction occur each day in your body?”
3.46*10^21 is the amount of cycles the ATP reaction occurs in the human body each day.