• Nutrition is the process of acquiring energy and carbon
• Organisms need energy for
  • Synthesis of substances for growth and repair.
  • 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
  • Beating of cilia and flagella

• 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 plants
• Chemoautotrophic– energy source is chemical substances and carbon source is Carbondioxide eg; nitrifying bacteria like Nitrobacter, Nitrosomonas

 

Heterotrophic nutrition – 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

 

• 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

• Most animals are holozoic.
• They ingest food into their alimentary canal.
• This mode of nutrition consists of five main steps ;
  • Ingestion
  • Digestion
  • Absorption
  • Assimilation
  • Ejection

 

Development of the Digestive System in animals to facilitate Holozoic nutrition

• All animals are heterotrophic
• Among them most of them show holozoic mode of nutrition
• All are multicellular
• When size increases, their energy requirement and complexity increases
• Thus they require much amount of energy
• Need for a specific system to ingest, digest, absorb, assimilate and eject the food emerged
• Lead to the origin of the digestive system

• 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, Loranthus

 

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)

• This is a special type of nutrition.
• These plants capture insects passively or actively and obtain specially their nitrogen requirements by digesting them.
• g., Nepenthes , Drosera , Utricularia