Primary productivity refers to the rate at which radiant energy is stored by photosynthetic and
chemosynthetic activity of producers; it is further distinguished as gross primary productivity (GPP)
and net primary productivity (NPP). It is expressed in terms of weight (g/m2/yr) or energy (kcal/m2).
Secondary productivity refers to the rates of energy storage at consumer levels. An understanding of
ecology is essential in the management of modern industrialized societies in ways that are
compatible with environmental preservation and enhancement. The branch of 6 ecology that deals
with predicting the impacts of technology and development and making recommendations such that
these activities will have minimum adverse impacts, or even positive impacts, on ecosystems may be
termed as Applied Ecology. It is a multidisciplinary approach. Interactions among living organisms
are grouped into two major groups viz., Positive interactions Negative interactions I. Positive
interactions Here the populations help one another, the interaction being either one way or
reciprocal. These include (i) Commen salism, (ii) Proto co-operation and (iii) mutualism. 1.
Commen salism In this one species derives the benefits while the other is unaffected. Eg. (i)
Cellulolytic fungi produce a number of organic acids from cellulose which serve as carbon sources for
non-cellulolytic bacteria and fungi. (ii) Growth factors are synthesised by certain microorganisms and
their excretion permits the proliferation of nutritionally complex soil inhabitants. 2. Protocooperation It is also called as non-obligatory mutualism. It is an association of mutual benefit to the
two species but without the co-operation being obligatory for their existence or for their
performance of reactions. Eg. N2 can be fixed by Azotobacter with cellulose as energy source
provided that a cellulose decomposer is present to convert the cellulose to simple sugars or organic
acids. Mutualism Mutually beneficial interspecific interactions are more common among organisms.
Here both the species derive benefit. In such association there occurs a close and often permanent
and obligatory contact more or less essential for survival of each. Eg. (i) Pollination by animals. Bees,
moths, butterflies etc. derive food from hectar, or other plant product and in turn bring about
pollination. (ii) Symbiotic nitrogen fixation: Legume - Rhizobium symbiosis. Bacteria obtain food from
legume and in turn fix gaseous nitrogen, making it available to plant. II. Negative interactions 7
Member of one population may eat members of the other population, compete for foods, excrete
harmful wastes or otherwise interfere with the other population. It includes (i) Competition, (ii)
Predation, (iii) Parasitism and (iv) antibiosis. (i) Competition It is a condition in which there is a
suppression of one organism as the two species struggle for limiting quantities of nutrients O2 space
or other requirements. Eg. Competition between Fusarium oxysporum and Agrobacterium
radio bacter. (ii) Predation A predator is free living which catches and kills another species for food.
Most of the predatory organisms are animals but there are some plants (carnivorous) also, especially
fungi, which feed upon other animals. a) Grazing and browsing by animals on plants. b) Carnivorous
plants such as Nepenthes, Dar ligtoria, Drosera etc. consume insects and other small animals for
food. c) Protozoans feeding on bacteria. (iii.) Parasitism A parasite is the organism living on or iA
parasite is the organism living on or in the body of another organisms and deriving its food more or
less permanently from its tissues. A typical parasite lives in its host without killing it, whereas the
predator kills its upon which it feeds. Eg. Species of Cuscuta (total stem parasite) grow on other
plants on which they depend for nourishment. Parasitism may occur even within the species.
Hyper parasites which are chiefly fungi growing parasitically on other parasites, (ie) Parasite on a
parasite. Eg. Cicinnobolus cesatii is found as hyperparasite on a number of powdery mildew fungi
This page editing tutorial and tips and tricks and always your favourite editing tutorial
ConversionConversion EmoticonEmoticon