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A population cycle in zoology is a phenomenon where populations rise and fall over a predictable period of time. There are some species where population numbers have reasonably predictable patterns of change although the full reasons for population cycles is one of the major unsolved ecological problems.
An example chemical cycle, a schematic representation of a Nitrogen cycle on Earth. This process results in the continual recycling of nitrogen gas involving the ocean. Chemical cycling describes systems of repeated circulation of chemicals between other compounds, states and materials, and back to their original state, that occurs in space ...
The dynamics of the elementary hypercycle can be modelled using the following differential equation: [3] ˙ = (+,) where =, =. In the equation above, x i is the concentration of template I i; x is the total concentration of all templates; k i is the excess production rate of template I i, which is a difference between formation f i by self-replication of the template and its degradation d i ...
Agricultural interest in 18th-century soil chemistry led to better understanding of nutrients and their connection to biochemical processes. This relationship between the cycles of organic life and their chemical products was further expanded upon by Dumas and Boussingault in a 1844 paper that is considered an important milestone in the development of biogeochemistry.
In a chemical reaction, the half-life of a species is the time it takes for the concentration of that substance to fall to half of its initial value. In a first-order reaction the half-life of the reactant is ln(2)/ λ , where λ (also denoted as k ) is the reaction rate constant .
A population inversion (N 2 > N 1) has thus been achieved between level 1 and 2, and optical amplification at the frequency ν 21 can be obtained. Because at least half the population of atoms must be excited from the ground state to obtain a population inversion, the laser medium must be very strongly pumped.
Bioaccumulation is the gradual accumulation of substances, such as pesticides or other chemicals, in an organism. [1] Bioaccumulation occurs when an organism absorbs a substance faster than it can be lost or eliminated by catabolism and excretion.
A biogeochemical cycle, or more generally a cycle of matter, [1] is the movement and transformation of chemical elements and compounds between living organisms, the atmosphere, and the Earth's crust. Major biogeochemical cycles include the carbon cycle , the nitrogen cycle and the water cycle .