1

2

What is Allocation of Resources?Resource Allocation involves partitioning of available energy and material intovarious vital activities or structures. If an organism allocates energy to onefunction, such as growth or reproduction, it reduces the amount of energyavailable to other functions, such as defense.

An organism must survive in order to reproduce.Failure to invest adequately in whatever it takes to survive therefore can resultin a failure to be reproductively successful. On the other hand, an organismthat invests excessively in survival can end up having few resources availableto devote to reproduction. The most fit organisms typically are those that bestbalance these conflicting demands.A good example of this conflict, as defined by the principle of allocation, can beseen with iteroparous organisms – organisms that display more than onereproductive episode per lifetime. That is, with such organisms excessiveinvestment in reproduction in one year can reduce an organism's potential tosurvive and/or reproduce in a subsequent year.

3

Semelparity and iteroparity refer to the reproductive strategy of an organism.A species is considered semelparous if it is characterized by a singlereproductive episode before death, and iteroparous if it is characterized bymultiple reproductive cycles over the course of its lifetime.

4

5

Semelparity also known as "big bang" reproduction, since the singlereproductive event of semelparous organisms is usually large as well as fatal.A classic example is Pacific salmon (Oncorhynchus spp.), which lives for manyyears in the ocean before swimming to the freshwater stream of its birth,spawning, and dying.

6

Introduction: The chemical reactions of metabolism are organizedinto metabolic pathways, in which one chemical is transformed through aseries of steps into another chemical, by a sequence of enzymes. Enzymesare crucial to metabolism because they allow organisms to drive desirablereactions that require energy. Energy release will not occur by themselves, butby coupling them to spontaneous reactions that will release energy. Enzymesact as catalysts that allow the reactions to proceed more rapidly. Enzymes alsoallow the regulation of metabolic pathways in response to changes inthe cell's environment or to signals from other cells.The word metabolism can also refer to all chemical reactions that occur inliving organisms, including digestion and the transport of substances into andbetween different cells, in which case the set of reactions within the cells iscalled intermediary metabolism or intermediate metabolism.Relations to ARs: Change in metabolic status, defined as change in theavailability of nutrients and energy to the tissues, is a powerful regulator ofreproductive function in both sexes.Significance: These enzyme-catalyzed reactions allow organisms to grow andreproduce, maintain their structures, and respond to their environments.

7

Metabolism is usually divided into two categories. Catabolism, that breaksdown organic matter and harvests energy by way of cellular respiration,and anabolism that uses energy to construct components of cells suchas 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 ofthe catabolic reactions is to provide the energy and components needed byanabolic reactions.The exact nature of these catabolic reactions differ from organism to organismand organisms can be classified based on their sources of energy and carbon(their primary nutritional groups).

8

9

10

Primary nutritional groups are groups of organisms, divided in relation to the nutrition modeaccording 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 carbonfor growth and development, and that produces its energy from oxido-reduction of an organiccompound. This group of organisms may be further subdivided according to what kind oforganic substrate and compound they use.Decomposers are examples of Chemoorganoheterotrophs which obtain carbon and electronreactions from dead organic matter. Herbivores and carnivores are examples of organisms thatobtain carbon and electron reactions from living organic matter.Chemoorganotrophs are organisms which oxidize the chemical bonds in organic compoundsas their energy source. Chemoorganotrophs also attain the carbon molecules that they needfor cellular function from these organic compounds. The organic compounds that they oxidizeinclude sugars (i.e. glucose), fats and proteins.All animals are chemoheterotrophs (meaning they oxidize chemical compounds as a source ofenergy and carbon), as are fungi, protozoa, and some bacteria. The important differentiationamongst this group is that chemoorganotrophs oxidize only organic compounds whilechemolithotrophs instead use inorganic compounds as a source of energy.

11

All sorts of combinations may exist in nature. For examplei. Most cyanobacteria are photoautotrophic, since they use light as an energy source, wateras electron donor, and CO2 as a carbon source.ii. Fungi are chemoorganotrophic since they use organic carbon as both an electron donorand carbon source.Eukaryotes are generally easy to categorise.i. All animals are heterotrophic, as are fungi.ii. Plants are generally photoautotrophic.iii. Some eukaryotic microorganisms, however, are not limited to just one nutritional mode.For example, some algae live photoautotrophically in the light, but shift tochemoorganotrophy in the dark.iv. Even higher plants retained their ability to respire heterotrophically on the starch at nightwhich had been synthesised phototrophically during the day.Prokaryotes show a great diversity of nutritional categories. For example,i. Purple sulfur bacteria and cyanobacteria are generally photoautotrophic whereas purplenon-sulfur bacteria are photoorganotrophic.ii. Some bacteria are limited to only one nutritional group, whereas others are facultativeand switch from one mode to the other, depending on the nutrient sources available.

12

Mixotroph or bitroph is an organism that can use a mix of different sources ofenergy and carbon, instead of having a single trophic mode on the continuumfrom 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 beeither eukaryotic or prokaryotic. They can take advantage of differentenvironmental conditions.Such mixotrophic organisms may dominate their habitat, due to their capabilityto use more resources than either photoautotrophic or organoheterotrophicorganisms.

13

14

15

16

17