The Metamorphosis of Butterfly
The first stage is the egg, The eggs hatch into
wormlike creatures known as larvae, The common name is caterpillar.
Caterpillars are busy and hungry. They may eat once or twice their own weight
in leaves each day.
In the third stage the caterpillar goes into a
resting state and is called a pupa. This stage may last two weeks; it may last
a whole winter. During this period the caterpillar changes into a full-grown
butterfly
Then, a beautiful, flying adult emerges. This adult
will continue the cycle.
Carbon
Cycle
The
movement of carbon, in its many forms, between the biosphere, atmosphere,
oceans, and geosphere is described by the carbon cycle, illustrated in the
adjacent diagram. The carbon cycle is one of the biogeochemical cycles. In the cycle there are various sinks, or stores, of carbon
(represented by the boxes) and processes by which the various sinks exchange carbon
(the arrows).
We
are all familiar with how the atmosphere and vegetation exchange carbon. Plants
absorb CO2 from the atmosphere during photosynthesis, also
called primary production, and release CO2 back in to the atmosphere
during respiration. Another major exchange of CO2 occurs
between the oceans and the atmosphere. The dissolved CO2 in the
oceans is used by marine biota in photosynthesis.
Two
other important processes are fossil fuel burning and changing land use. In
fossil fuel burning, coal, oil, natural gas, and gasoline are consumed by
industry, power plants, and automobiles. Notice that the arrow goes only one
way: from industry to the atmosphere. Changing land use is a broad term which
encompasses a host of essentially human activities. They include agriculture,
deforestation, and reforestation.
The
adjacent diagram shows the carbon cycle with the mass of carbon, in gigatons of
carbon (Gt C), in each sink and for each process, if known. The amount of
carbon being exchanged in each process determines whether the specific sink is
growing or shrinking. For instance, the ocean absorbs 2.5 Gt C more from the
atmosphere than it gives off to the atmosphere. All other things being equal,
the ocean sink is growing at a rate of 2.5 Gt C per year and the atmospheric
sink is decreasing at an equal rate. But other things are not equal. Fossil
fuel burning is increasing the atmosphere's store of carbon by 6.1 Gt C each
year, and the atmosphere is also interacting with vegetation and soil.
Furthermore, there is changing land use.
The
carbon cycle is obviously very complex, and each process has an impact on the
other processes. If primary production drops, then decay to the soil drops. But
does this mean that decay from the soil to the atmosphere will also drop and
thus balance out the cycle so that the store of carbon in the atmosphere will
remain constant? Not necessarily; it could continue at its current rate for a
number of years, and thus the atmosphere would have to absorb the excess carbon
being released from the soil. But this increase of atmospheric carbon (in the
form of CO2) may stimulate the ocean to increase its uptake of CO2 .
What
is known is that the carbon cycle must be a closed system; in other words,
there is a fixed amount of carbon in the world and it must be somewhere.
Scientists are actively investigating the carbon cycle to see if their data
does indeed indicate a balancing of the cycle. These types of investigations have led many scientists to believe
that the forests of the Northern Hemisphere are, in fact, absorbing 3.5 Gt C
per year, and so changing land use is actually removing carbon from the
atmosphere (~2 Gt C/year), not increasing it as the diagram shows. Experiments
are ongoing to confirm this information.
