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What is Allocation of Resources?
Resource Allocation involves partitioning of available energy and material into
various vital activities or structures. If an organism allocates energy to one
function, such as growth or reproduction, it reduces the amount of energy
available to other functions, such as defense.
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An organism must survive in order to reproduce.
Failure to invest adequately in whatever it takes to survive therefore can result
in a failure to be reproductively successful. On the other hand, an organism
that invests excessively in survival can end up having few resources available
to devote to reproduction. The most fit organisms typically are those that best
balance these conflicting demands.
A good example of this conflict, as defined by the principle of allocation, can be
seen with iteroparous organisms – organisms that display more than one
reproductive episode per lifetime. That is, with such organisms excessive
investment in reproduction in one year can reduce an organism's potential to
survive and/or reproduce in a subsequent year.
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Semelparity and iteroparity refer to the reproductive strategy of an organism.
A species is considered semelparous if it is characterized by a single
reproductive episode before death, and iteroparous if it is characterized by
multiple reproductive cycles over the course of its lifetime.
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Semelparity also known as "big bang" reproduction, since the single
reproductive event of semelparous organisms is usually large as well as fatal.
A classic example is Pacific salmon (Oncorhynchus spp.), which lives for many
years in the ocean before swimming to the freshwater stream of its birth,
spawning, and dying.
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Introduction: The chemical reactions of metabolism are organized
into metabolic pathways, in which one chemical is transformed through a
series of steps into another chemical, by a sequence of enzymes. Enzymes
are crucial to metabolism because they allow organisms to drive desirable
reactions that require energy. Energy release will not occur by themselves, but
by coupling them to spontaneous reactions that will release energy. Enzymes
act as catalysts that allow the reactions to proceed more rapidly. Enzymes also
allow the regulation of metabolic pathways in response to changes in
the cell's environment or to signals from other cells.
The word metabolism can also refer to all chemical reactions that occur in
living organisms, including digestion and the transport of substances into and
between different cells, in which case the set of reactions within the cells is
called intermediary metabolism or intermediate metabolism.
Relations to ARs: Change in metabolic status, defined as change in the
availability of nutrients and energy to the tissues, is a powerful regulator of
reproductive function in both sexes.
Significance: These enzyme-catalyzed reactions allow organisms to grow and
reproduce, maintain their structures, and respond to their environments.
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Metabolism is usually divided into two categories. Catabolism, that breaks
down organic matter and harvests energy by way of cellular respiration,
and anabolism that uses energy to construct components of cells such
as proteins and nucleic acids.
Catabolism is the set of metabolic processes that break down large molecules.
These include breaking down and oxidizing food molecules. The purpose of
the catabolic reactions is to provide the energy and components needed by
anabolic reactions.
The exact nature of these catabolic reactions differ from organism to organism
and organisms can be classified based on their sources of energy and carbon
(their primary nutritional groups).
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Primary nutritional groups are groups of organisms, divided in relation to the nutrition mode
according to the sources of energy and carbon, needed for living, growth and reproduction.
A chemoorganoheterotrophic organism is one that requires organic substrates to get its carbon
for growth and development, and that produces its energy from oxido-reduction of an organic
compound. This group of organisms may be further subdivided according to what kind of
organic substrate and compound they use.
Decomposers are examples of Chemoorganoheterotrophs which obtain carbon and electron
reactions from dead organic matter. Herbivores and carnivores are examples of organisms that
obtain carbon and electron reactions from living organic matter.
Chemoorganotrophs are organisms which oxidize the chemical bonds in organic compounds
as their energy source. Chemoorganotrophs also attain the carbon molecules that they need
for cellular function from these organic compounds. The organic compounds that they oxidize
include sugars (i.e. glucose), fats and proteins.
All animals are chemoheterotrophs (meaning they oxidize chemical compounds as a source of
energy and carbon), as are fungi, protozoa, and some bacteria. The important differentiation
amongst this group is that chemoorganotrophs oxidize only organic compounds while
chemolithotrophs instead use inorganic compounds as a source of energy.
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All sorts of combinations may exist in nature. For example
i.
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Most cyanobacteria are photoautotrophic, since they use light as an energy source, water
as electron donor, and CO2 as a carbon source.
Fungi are chemoorganotrophic since they use organic carbon as both an electron donor
and carbon source.
Eukaryotes are generally easy to categorise.
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All animals are heterotrophic, as are fungi.
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Some eukaryotic microorganisms, however, are not limited to just one nutritional mode.
For example, some algae live photoautotrophically in the light, but shift to
chemoorganotrophy in the dark.
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Plants are generally photoautotrophic.
Even higher plants retained their ability to respire heterotrophically on the starch at night
which had been synthesised phototrophically during the day.
Prokaryotes show a great diversity of nutritional categories. For example,
i.
ii.
Purple sulfur bacteria and cyanobacteria are generally photoautotrophic whereas purple
non-sulfur bacteria are photoorganotrophic.
Some bacteria are limited to only one nutritional group, whereas others are facultative
and switch from one mode to the other, depending on the nutrient sources available.
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Mixotroph or bitroph is an organism that can use a mix of different sources of
energy and carbon, instead of having a single trophic mode on the continuum
from complete heterotrophy at one end to autotrophy at the other.
Possible combinations are photo- and chemotrophy, litho- and organotrophy,
auto- and heterotrophy or other combinations of these. Mixotrophs can be
either eukaryotic or prokaryotic. They can take advantage of different
environmental conditions.
Such mixotrophic organisms may dominate their habitat, due to their capability
to use more resources than either photoautotrophic or organoheterotrophic
organisms.
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