Nutrition and its need

Nutrition is the process of acquiring energy and carbon. Organisms need energy for synthesis of substances for growth and repair. Ex: Protein synthesis, active transport of substances into and out of cells against  concentration gradient (Sodium-Potassium pump), electrical transmission of nerve impulses, mechanical contraction of muscle and beating of cilia and flagella. lets find out more about nutrition.

 Different modes of nutritional patterns in the living world:

                       •    Living organisms can be grouped on the basis of their source of energy or source

                        of carbon

                       •    Organisms which have an inorganic source of carbon  such as carbon dioxide are

                        described as autotrophic

                       •    Organisms having an organic source of carbon are described as heterotrophic

                       •   Organisms using light energy are described as phototrophic

                       •   Organisms using chemical energy are described as chemotrophic

•   Autotrophs synthesize their own organic  requirements from simple inorganic

                        materials

                       •   Autotrophic nutrition is of two types:

                        •   Photoautotrophic – Energy source is sunlight and carbon source is

                           carbondioxide.eg: cyanobacteria,  green bacteria ,green plants

                        •   Chemoautotrophic- energy source is chemical substances and carbon source is

                           Carbondioxide eg; nitrifying bacteria like  Nitrobacter, Nitrosomonas

                       •   Heterotrophic organisms feed on an organic source of carbon. All  animals and

                        fungi and majority of bacteria are heterotrophic

                        •    Modes of heterotrophic nutrition

                        •    There are three types:

                            •   Saprotrophic

                            •   Holozoic

                            •   Symbiotic

        Saprotrophic nutrition

                                  Organisms which feed on dead or decaying organic matter are called

                                saprotrophs. eg: Many fungi and bacteria. Saprotrophs secrete  enzymes on

                                to the dead organic matter  and  digest. Soluble end products of this

                                extracellular digestion are then absorbed and assimilated by the saprotrophs

        Holozoic nutrition

                                  Most animals are holozoic. They ingest food into their alimentary canal.

                                This mode of nutrition consists of five main steps ;

                                  Ingestion, digestion, absorption, assimilation and ejection.

        Symbiosis

                                 Two different species of organisms living together. It is divided into three

                                groups.

                                •   Mutualism

                                •   Parasitism

                                •   Commensalism

                                 •   Mutualism

                                        It is a close association between two living organisms of different

                                   species, which is beneficial to both partners. e.g., Legume root nodules

                                   and  Rhizobium

                                 •   Parasitism

                                   It is a close association between two living organisms of different

                                   species, which is beneficial to one (parasite) and harmful to the other

                                   (host)

                                                    ,

                                   e.g.,  Plasmodium Necator americanus,Cuscuta

                                 •   Commensalism

                                   It is a close association between two living organisms of different

                                   species which is beneficial to one and does not affect the other. e.g.,  Sea

                                   anemone and hermit crab, epiphytes (orchids)

                       •   Insectivorous plants

                        This is a special type of nutrition. These plants capture insects passively or actively

                        and obtain  specially their nitrogen requirements by digesting them.

                        e.g.,   Nepenthes, Drosera, Utricularia