Nutrition is one of the characteristics of living organisms. It is the process by which living organisms obtain and utilize materials from the external environment for metabolic activities such as respiration, growth, reproduction etc.
These macromolecules obtained from the environment are used to meet the energy requirements, building of body organs and repair of worn-out tissues. These molecules are taken as food. Hence, we can define food as any substance which when absorbed into the body of cells , yields energy and materials for growth, repairs of damaged tissues and regulation of body processes without substantial causing
It is one of the basic characteristics of living organisms as it is a pool for survival. Animals and plants undergo so many movements and processes to achieve nutrition. All living organisms posseses one or more features which enables it to successfully secure food from the environment.
Aquatic organisms develop breathing roots in order to survive, animals such as hawk, hyena, lion etc develop features for the tearing of fresh for nutritional purposes.
Mode of nutrition
Living organisms have evolved different mode of nutrition. This mode of nutrition ranges from simple prokaryotic cells such as bacteria to more complex being such as man.
Organisms can be classified into two major groups based their mode of feeding viz
Autotrophic mode of nutrition (self feeders)
This mode of nutrition is carried out by organisms which manufacture their own food through photosynthesis or chemosynthesis.
photosynthesis involves the use of sun’s energy (light) in the presence of chlorophyll, water and carbon dioxide to yield starch and oxygen. Chlorophyll is is the pigment that gives leaves its greenish coloration. It also traps sun energy which is the driving force of photosynthesis. Photosynthesis occurs majorly in leaves and other greenish part of plpla
Chemosynthesis occurs in organisms that breakdown inorganic compounds and uses it to generate carbohydrates, other necessary molecules and energy. Such organisms includes sulphur bacteria, nitrosomonas etc. All organisms in this group or mode of nutrition are referred to as autotrophs.
Heterotrophic mode of nutrition (dependent feeders)
This group of organisms are incapable of manufacturing their own food from simple inorganic compounds as they lack the presence of chlorophyll in their system. They are dependent on the autotrophs or the primary producers for their metabolic requirements. These group of animals are known as heterotrophs. Heterotrophs are further split into macrophagous organisms an microphagous organisms.
Macrophagous organisms are those animals that take in large molecules of food and have evolved teeth for the breakdown of the food in the mouth, in order to fit the size of the esophagus. All heterotrophs are primarily animals.
They can be further split into
a. Holozoic nutrition: in this type of nutrition, food molecules are taken as solid organic materials which are eaten, digested and absorbed by the organism. They exhibit different efficient digestive systems that enable them to digest food obtained.
b. Saprophytic nutrition: in this type of nutrition, non chlorophyll containing plants feed on dead decaying organic matter. They are known as saprophyte. Their mode of digestion is external, as the saprophyte releases digestive enzymes that breakdown the dead decaying organic matter before assimilation.
c. Symbiotic nutrition: this is a type of nutrition in which two types of organisms of different species live together to advantage of each other. These organisms are found in association in which one provides a basic need of the other organisms, and in return the organism houses or also provide another basic need of the other.
Examples can be seen in the association of alga and fungus in lichens, cellulose digesting bacteria and herbivores, hermit crab and sea anemone etc.
d. Parasitic mode of nutrition: this is a form of nutrition or association where an organism known as parasite lives in/on another organism where it obtains nutrition and shelter, thereby causing substantial harm to the host. Parasites includes licks, dodder plant, tape worm, plasmodium etc.