AP Env. Sci
You are to include your WIKI answers to chapter 4 questions below. Please include the number
of the question.
Karli:
5. Make a list of the food you have eaten today and trace each type of food back to a particular
producer.
Cereal (milk and Cheerios)- The Cheerios are made from wheat which belongs to the first
trophic level as it grows via photosynthesis and is its own producer. Milk is the byproduct of
cows (generally), so the cow ate grass or grain that are both on the first trophic level and are the
producers for the cows. The cows, as assumed, are the primary consumers on the second trophic
level as they eat the producers directly. The milk is then taken from the cow.
Ravioli- To make ravioli, you need noodles, sauce, and beef. The noodles are a product of wheat
which acts as its own producer while the sauce is made of tomatoes and herbs which all use
photosynthesis making them their own producers as well. The beef comes from the cow, a
primary consumer of the second trophic level that feeds on grass and other vegetation as well as
grain, which are all primary consumers of the first trophic level.
Apple- An apple is its producer as it contains seeds to plant more trees which in turn, use
photosynthesis to grow and bloom apples.
Chex Mix-The mix of Chex cereal and pretzels is comprised of enriched flour (made by grinding
grains/roots), whole wheat, vegetable oil (made from seed extract) and sugar (from sugar cane).
All of these some directly from the first trophic level as the sources of these all return to the
producers that use photosynthesis to function.
Evon:
4a. How would you set up a self-sustaining aquarium for tropical fish?
The important limiting factors for aquatic ecosystems include: temperature, sunlight, nutrient
availability, and dissolved oxygen content. In order to provide tropical fish with a self-sustaining
aquarium, there will need to be systems that account for all of these factors. To acquire the
accurate temperature and sunlight needed, the aquarium would need to be placed by a window
that generates sufficient sunlight or contain a light and heater. To manage the nutrient
availability and DO content, soil and plants will be needed.
4b. Suppose you have a balanced aquarium sealed with a clear glass top. Can life continue in the
aquarium indefinitely as long as the sun shines regularly on it?
There is no guarantee that life can continue on indefinitely/forever in the aquarium, but a few
years could be possible. For a container that only gets light from the sun, it needs enough air
space for oxygen to be stored for the night, as no oxygen is produced without light, and if the
oxygen runs out the ecosystem will fail. Putting the tank in front of a window can raise the light
level, but if the sun hit the tank directly, it can also raise the water temperature. As the water gets
warmer, it holds less oxygen—consistent monitoring would be required.
4c. A friend cleans out your aquarium and removes all the soil and plants, leaving only the fish
and water. What will happen? Explain.
Plants give off dissolved oxygen, which the fish needs to breathe. The plants and soil act as a
natural filtration system, but will need to be replaced in order for the fish to live due to the fact
that plants only produce oxygen during the day. Although the fish won’t necessarily die, it would
not be a safe environment for them.
Cadence:
7. Use the second law of thermodynamics to explain why many poor people in developing
countries live on a mostly vegetarian diet.
The second law of thermodynamics states that when energy is changed from one form to
another, some of the useful energy is always degraded to lower quality, more dispersed,
less useful energy. It takes much more energy, water and time to create a pound of meat
than it does a pound of grain or vegetables. From a thermodynamical standpoint, a pound
of grain has a certain amount of energy in it. If you eat it, you get all of this energy - but if
you feed it to a cow, part of it will be burned, and only a portion of it will be stored. Plants
derive their energy from the sun. Animals derive theirs from plants, or from other animals
who derive it from plants. But the animals use most of their energy to build and maintain
themselves. In order to best absorb the energy from the available food resources, people in
developing countries must consume vegetables at less quantities to be able to access the
same amount of energy someone in a more developed country would get from a
hamburger, as the energy in the hamburger has been through the plants the cow ate before
it was a hamburger. However, the plants the cow ate are closer in the energy-entropy chain
to the sun, and therefore have more energy than the beef of the cow itself.
Mackenzie:
9. Carbon dioxide (CO2) in the atmosphere fluctuates significantly on a daily basis. Why are
CO2 levels higher in the day than at night?
In large, the fluctuation in CO2 levels from day to night is a combination of a result from the
ocean temperature changes, and plant respiration. The ocean is a carbon sink and it
contains a large portion of the atmosphere's carbon, and when it warms up, some of that
dissolved CO2 is added back into the atmosphere, raising it's concentration. Because it is
warmer during the day than at night, the ocean is able to hold more CO2 at night, which
lowers the CO2 in the atmosphere. However, CO2 levels being higher during the day is
counter-intuitive because when looking at plant respiration and the calvin cycle, we see that
plants take in CO2 during the day (light dependent reaction) which lowers the daytime CO2
levels, and release CO2 at night (light-independent reaction). Therefore plants contribute to
higher levels of CO2 at night, but the ocean's contribution to the carbon cycle is more
significant and atmospheric CO2 levels are higher in the day.
Adrienne:
2. Why are microbes the real rulers of the earth?
Microbes are prokaryotic organisms that are so small, they can only be seen with the aid of a
microscope. The cells of a prokaryotic organism are different than our cells (or other eukaryotic
cells) because they don’t have a distinct nucleus or other internal parts enclosed by membranes.
Examples of microbes include bacteria, protozoa, fungi, and yeast. Although most of us don’t
realize, there are trillions of microbes all around us. Billions of them can even be found inside
our body.
Microbes are the real rulers of the earth because they perform vital functions that allow humans
and other organisms to live. Many of us are aware of some microbes in the form of infectious
bacteria and think of all microbes as a threat to our health. The fact is that only a minority of
microbes harm us, while trillions of others perform important tasks to keep us alive. The jobs
that microbes do which are vital to our survival include:
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converting nitrogen gas in the atmosphere into forms that plants can take up from the soil
as nutrients
producing foods such as bread, cheese, yogurt, vinegar, beer, and wine
decomposing organic wastes in soil into nutrients that can be taken up by plants
help purify the water we drink by breaking down wastes
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microbes in your nose prevent harmful bacteria from reaching your lungs
some are the source of disease-fighting antibiotics, including penicillin, erythromycin,
and streptomycin.
help control plant diseases and populations of insect species that attack our food crops
genetic engineers are developing microbes that can extract metals from ores, break down
various pollutants, and help clean up toxic waste sites.
One highlight from this list of tasks that microbes can perform would be that they produce
nutrients from nitrogen gas in the atmosphere as well as from decomposing organic wastes.
These nutrients can be transferred from the soil to plants. The plants are then providing energy to
humans; either directly, or indirectly through the food chain.