Biology June 2003 Essay
Cycles in Biology
Biology could be said to be constrained in its actions by a number of vital cycles
which without life could not exist. There are ecological cycles, cell cycles and
physiological cycles at just a glance.
An extremely important cycle is the Nitrogen cycle, with the earth’s atmosphere being
made up of roughly 78% Nitrogen it is the largest pool of Nitrogen, Nitrogen is
present in all Amino acids (for example), and is essential for any life.
The first stage of the Nitrogen cycle is Nitrogen cycle where nitrogen is converted
from its inert chemical N2 to NH3 by a number of Prokaryotes. Plants can then absorb
the Ammonium through their root hairs via a process called Assimilation. It is worth
noting that some plants have nodules and a relationship with bacteria that allows
direct N2 fixation to Ammonia. Animals can then absorb nitrogen in Amino acids (for
example) when food is consumed.
When a plant dies or an animal excretes the nitrogen will be organic (urea for
example) and this is turned into Ammonia by certain bacteria by a process called
Ammonification. Ammonia is then converted to nitrate by the process Nitrification
(from soil living bacteria) and finally Dentrification which is the process of reducing
nitrates back to nitrogen gas. This final stage completes the cycle and restores the
amount of Nitrogen gas in the atmosphere.
While this is essential to the support life, life itself is only achievable through the cell
cycle. The cell cycle is, in short, Mitosis in which two identical daughter cells form
from one eukaryotic cell. There are four processes of Mitosis which are Prophase,
metaphase, anaphase and telophase. There is also interphase which is hugely
important but occurs outside of Mitosis – interphase is the action of all genetic data in
the cell being replicated.
Talk about Mitosis stuff
Nervous system
Predator Prey cycle
End.