Nutrition is define as the process by which living organisms obtain and make use of food rich compound to obtain energy. Or a process <here by living organism obtain and assimilate food nutrients. Green plants such as protoctist manufacture their own food substances from simple inorganic materials.

            Organisms that are capable of manufacturing their own food are known as Autrotrophs and this type of nutrition is called Autotrophic nutrition. While some organism are not capable of manufacturing their own food i.e they depend on read-made food or food manufactured by autotroph as such this type of nutrition is called Heterotrophic nutrition.

            Heterotrophic nutrition is divided into three

-HOLOZOIC                         -PARASITIC              -SAPROPHITIC

-PARASITIC NUTRITION

These are organism that live on or in the body of another living organism of a different specie obtaining food, shelter, protection or maybe harmful to the host. Those that live inside the host are known as endoparasite and those that live outside the host are known as ectoparasite.

-HOLOZOIC NUTRITION

            This are organisms that obtain solid organic complex food that are broken down during digestion into simpler molecules from which energy is obtain e.g Amoeba.

-SAPROPHITIC NUTRITION

            They are organisms that breakdown dead decay organic material or matter to obtain energy e.g bread mould.

                        Heterotrophic nutrition is divided into: Chemosynthesis and photosynthesis.

-CHEMOSYNTHESIS

            It is a process were by certain bacteria manufacture organic substances by combining carbondioxide and water but energy comes from oxidation of various inorganic materials such as ; ammonia, hydrogen sulphide and iron(II) and not from sunlight.

- PHOTOSYNTHESIS

            It is a process by which green plant bring protoctists can manufacture organic substances such as carbohydrate(glucose) by combining inorganic compound such as carbondioxide , water in the presence of sunlight energy absorb or tract by chlorophyll by the release of oxygen as a byproduct or waste product.

6CO₂+6H₂O-^{sunlightenergy} C₆ H₁₂O₆+6O₂

HOW A LEAF IS ADAPTED

• A leaf has a flat surface which increases the surface area for the absorption of CO₂ an sunlight via the stomata to the mesophyll cells
• The leaf are thin so as to minimize the distance over which gases can diffuse.
• The leaf has numerous stomata that permit the diffusion of gases in and out of the leaf.
• The chloroplast found in the ground cells, mesophyll cells and the palisade cells allows or permit the absorption  of sunlight energy.
• The veins and the midribs of the leaf helps to carry food and water manufactures in the lamina to other part of the plant.
• The palisade cells are closely feeded together to reduce excess water lost and the arrangement of right angle help for maximum absorption of sunlight.
• The curticle of the leaf prevent excess water lost by transpiration and evaporation.
• The leaves do not overlap, hence each leave can absorb a maximum amount of sunlight.
• The curticle is transparent for easy penetration of sunlight energy for the process of photosynthesis
• The mesophyll mayers or cell has or cell has numerous intercellular air space which facilitates the diffusion of gases