Cycles Scavenger Hunt
The ___hydrologic_____ cycle is driven by the power of the Sun’s
energy. The sun causes ___evaporation________of water on the surface
of the oceans. Approximately 80% of all evaporation on Earth occurs
over __tropical_______oceans where the water and air is warmer. Once
the gaseous water (water vapor) is in our atmosphere, it ___condenses__
into tiny droplets which cling to dust particles. The tiny dust and dirt
particles known as “aerosols” are called “__condensation_____
___nuclei____”. These particles are vital to the process of condensation.
These tiny water droplets form clouds. Once heavy enough, these
droplets fall to Earth as __precipitation____. Once the water hits the
Earth’s surface, it has a few options…the first is ___infiltration_____
which occurs when water penetrates Earth’s surface and becomes
groundwater. When the ground is particularly _impermeable_____ due
to pavement, or saturated already, the water may runoff causing
flooding. ____Transpiration___ is how plants contribute to the water
cycle. It is the evaporation of water into the atmosphere from the leaves
and stems of plants through microscopic openings called “_stomata__”.
_Evapotranspiration__, which combines evaporation and
_transpiration___ accounts for approximately 10% of all evaporating
water. The amount of precipitation and evaporation is ___balanced___
throughout the world. Sometimes, one part of the world is experiencing
a drought, while another is experiencing flooding rains.
_Nitrogen _ is critically important to the formation of _amino_
___acids__, which are monomers of proteins. The basic structure of the
amino acid includes two _functional____ __groups___. The one which
contains nitrogen is known as the _amine___ _group___, and at the
other end, a _carboxyl___ __group__ (which is a carbon linked with
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oxygen and hydrogen). There are _21_ known amino acids, which in
turn form all of the proteins in your body, and all other organisms’
bodies for that matter. _Enzymes___ carry out almost all of the chemical
reactions in your body, and are proteins too. The chief reservoir of
nitrogen on Earth is the _atmosphere___, which is about 78% nitrogen.
This form of nitrogen is not assimilated by organisms besides one
special group, which __fix__ nitrogen in such a way as to make it
useable by other life. Nitrogen can also be __fixed__ by the action of
__lightning_____, which actually “burns” it out of the atmosphere,
creating __nitrate__(NO3) which is nitrogen bound to three oxygen
atoms. Nitrogen fixing bacteria called rhizobium are found in the roots
of __legumes___, and fix nitrogen either in the form of _nitrates__
(NO3), or _ammonia__ (NH3). Since NH3 is rather toxic, we are
fortunate that there are __nitrifying____ bacteria in the soil and in the
water which take up ammonia and convert it to _nitrite___, (NO2).
Ammonia is also somewhat toxic, but __nitrate___ bacteria, take it and
convert it to nitrate, which can be taken up by plants to continue the
cycle. _Assimilation____ is the process whereby plants absorb (NH3) ,
_ammonium___ ions (NH4), and nitrate ions (NO3-) through their roots.
Most plants can take up ___nitrate_____ and convert it to amino acids,
which are, of course, the building blocks of proteins. __Heterotrophs__
acquire all of their amino acids when they eat plants (or other animals
that consume plants). When organisms die and ___decompose_____, or
release __waste________ the nitrogen is returned to the soil, usually in
the form of __ammonia____. This NH3 or NH4 is a product of
decomposing bacteria, and in this state, may be reused by plants,
especially with the help of nitrate bacteria. If this is indeed a cycle…how
is N2 returned to the atmosphere? It turns out that there are
__denitrifying____ bacteria (usually anaerobic) which take the nitrites
and nitrates and combine the nitrogen back into _N2_ gas, and nitrous
oxide. This, of course, sends it back into the atmosphere to begin the
cycle all over again.
___Carbon dioxide____ is a molecule that has a huge capacity to
absorb great amounts of thermal energy. It is this molecule that is most
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often attributed to global warming. The __carbon___ __cycle__
moves and stores carbon in the __biosphere____ (living subsystem),
lithosphere, __hydrosphere_____(watery subsystem) and atmosphere.
Carbon is stored in the biosphere as __organisms____, and in the
atmosphere as _carbon___ ___dioxide __ gas. In the lithosphere,
which includes the solid part of Earth’s crust, both continental and
oceanic…as well as soil organic matter, you will also find Earth’s fossil
fuel deposits, and sedimentary rock deposits, which are generally
composed of substances like __limestone___ or calcium carbonate
(CaCO3). In the oceans, rivers and streams, carbon is stored as dissolved
carbon dioxide gas and as calcium carbonate shells in marine organisms
(although parts of the hydrosphere overlap with the atmosphere, because
remember, _water___ can exist in three states on Earth, and when it is a
gas, it is in the atmosphere).
Humans have altered the ___carbon____ __ cycle___ through fossil
fuel burning, deforestation, and land-use change. The net result of these
processes is an increasing concentration of carbon dioxide in the
atmosphere. Remember, a carbon __sink___ is an area that “stores”
carbon. The largest storage place for carbon on Earth is the
__ocean____ and marine ___sediments_____.
__Phosphorus______ is the simplest of all the nutrient cycles, as it
doesn’t exist in the __atmosphere_____ for the most part…but it is
found in soil, rock, and sediment. Also, of all the cycles, this one is more
__local_____ rather than global… than the others. It is usually released
from sediments in the form of ___phosphate___ (PO4-3), which is very
__soluable_______and can be dissolved easily in water and then
absorbed from the soil by plants. Phosphorus is a __limiting________
__factor_____ in the growth of plants, so plants that are exposed to
minimal amounts of phosphorus are usually __stunted_______.
Phosphorus is an important nutrient because it is an essential building
block of _nucleic__ __acids____, which of course compose DNA and
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ATP. Humans have affected the natural cycling of this nutrient by
mining phosphorous rich rocks for __fertilizers______. When we add
those to soil it interacts with the hydrologic cycle, and becomes leached
out after rain, and washed to rivers and eventually into the __ocean____
where it can cause _artificial_________ _eutrophication____. The
resulting _algal__ __bloom____ from artificial addition of these
nutrients has a short life span. When the algae dies, it sinks to the
bottom, and through the process of _decomposition__, consumes
massive amounts of _dissolved_____ _oxygen___. This depletes the
oxygen levels to such an extent as to rob the aquatic vertebrates and
invertebrates of their oxygen source…which causes a _fish_____
__kill___. The phosphorus is simply returned to the sediment when
organisms that have incorporated it into their systems die and
__decompose______.
The _rock___ __cycle_____ has the ability to take sediment over time
and turn it into a solid through the process of lithification. Over
thousands of years, a sandy beach might become part of a
__sedimentary______ ___rock__ known as sandstone. Sedimentary
rocks make up about three-quarters of the rocks at the Earth surface.
__Fossils______ of ancient living things are preserved in sedimentary
rocks too. These rocks help us solve puzzles about the past
__environments______.
_Igneous______ __rocks__ form when molten rock cools and
becomes solid. Molten rock is called _magma___ when it is below the
Earth’s surface and __lava__ when it is above. These volcanic rocks are
divided into two groups, based on where the rock forms. Those that form
below the Earth’s surface are called _intrusive____ igneous rocks. They
form when magma enters an underground chamber, cools very slowly,
and forms rocks full of large crystals. Those that form above the Earth’s
surface are called __extrusive___ igneous rocks. These rocks, also
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called volcanic rocks, form when lava cools quickly at or above the
Earth’s surface and are full of _tiny___ crystals. _Metamorphic______
rocks form in a place that is very _hot__and under high _pressure____.
You can find such a place where Earth's __tectonic____ plates are
coming together. There, the colliding plates squish rocks, and hot pools
of magma heat them deep underground. When minerals within
__metamorphic_____ rock are organized a way that makes them flake
apart, it is called _foliation______ . Some metamorphic rocks are
_foliated____ and others are nonfoliated.
The cycling of _sulfur_____is important for proteins, which have
the ___sulfur__- containing amino acids cysteine and cystine. The
__sulfur_____ cycle is similar to the phosphorus cycle, as it only
contains a brief atmospheric component. __Sulfur______ is mainly
found in rocks and soil (coal, oil, and peat) as sulfate minerals.
Weathering (by the _hydrologic___ cycle) exposes sulfates in the rocks,
and helps remove them into the soil and aquatic ecosystems. In both
these ecosystems, plants and other photosynthetic organisms take up and
assimilate sulfates into their tissues.
__Consumers_____ eat the plants and likewise assimilate sulfates into
their tissues. Death and __decomposition___ convert organic sulfates
into inorganic sulfates. Animal __waste___ also add sulfates to the soil
or water. Sulfates then recycle. There is one important difference
between the sulfur cycle and the phosphorus cycle, however. The sulfur
cycle does contain a small atmospheric component. Atmospheric
hydrogen sulfide sources include _volcanoes___ and ___power____
__plant_____ emissions from burning fossil fuels which contain sulfur.
In the atmosphere, hydrogen sulfide gas quickly breaks down into sulfur
dioxide, where it combines with water vapor to form _sulfuric___
__acid___. This combines with rain water to form _acid_ __rain___,
thereby returning sulfur to the soil and water ecosystems.
Molecular _oxygen_____ is a critical substance for living things. It
is a by-product of _photosynthesis_______ and a reactant in respiration.
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__Oxygen____ is very chemically reactive. The combination of biology
and chemistry help to cycle oxygen on Earth. When talking about the
way that oxygen cycles on Earth, you will always see it in association
with the carbon cycle. They work hand in hand, cycling these two
nutrients in a vital way.
The main supply of __oxygen__ on Earth is the atmosphere, which
is 21% this gas. Oxygen cycles between the atmosphere, living
organisms, aquatic ecosystems and Earth’s crust. It can be removed, or
added. Processes responsible for the removal include chemically
reacting with rocks and minerals exposed by weathering. Certain red
rocks were originally composed of _iron___ which has reacted with the
O2 in the atmosphere to produce “rust”, or _iron__ _oxide____.
__Respiration___ by producers, consumers, and decomposers also
removes oxygen from the atmosphere. Oxygen is produced through the
process of photosynthesis, when plants use CO2 and _water___in the
presence of sunlight, and generate __glucose_____ and oxygen.
_Photochemical_____ ____dissociation_____ occurs when sunlight
breaks down water vapor in the atmosphere, into hydrogen and oxygen.
The hydrogen escapes to outer space and the oxygen remains. This
oxygen can combine with diatomic molecular oxygen to produce
triatomic oxygen (O3), also known as __ozone____. This gas is a vital
part of Earth’s atmosphere, at least where it belongs, in an area of the
__stratosphere_____ (atmospheric layer), known as the _ozone___
layer. The formation of triatomic oxygen on Earth MUST have predated
the origin of life, as living cells and more complex tissue could not
survive without its protective value. O3 sits in this layer and absorbs
most of the incoming ultraviolet radiation, which is destructive to cells.
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