Autotrophic and heterotrophic nutrition - Biologie

                Autotrophic and heterotrophic nutrition:
Exist 4 kinds of nutrition and depends on organism. Autotrophic and heterotrophic is characteristic only for plants and animals. Humans, like all animals eat food which has be made by other organisms. The food we eat contains organic substances, especially carbohydrates, fats and proteins which have been made by plants. Plants are able to make these substances from inorganic ones; they use carbon dioxide and water to make carbohydrates by photosynthesis. The  addition of a few inorganic minerals ion, such as nitrates and  phosphates, enables them to synthesize all the other substance which they require ,such as proteins and nucleic acids.
All animals on organic substances which have originally been made by plants, both for their source of energy and for materials from which to build their bodies. Animals are therefore said to be  heterotrophic ,while plants are autotrophic .Hetero means ‘different’ or ‘other’, whereas   means ‘auto’ or ‘self’. Animals are depend on food produced by other organism, but plants can make our own food.
Animals  are not only group of organism which feed  heterotrophically. Fungi also are hetrotrophs, as are many protoctist   and  prokaryotes. All of them are dependent on food made by autotrophs.
                        Types of heterotrophic nutrition: 
Heterotrophic organisms have evolved many different ways of obtaining the organic nutrients they need.
 Holozoic nutrirtion
Is the method by which humans and other mammals feed, as well as many other animals such as insects .food, in solid or liquid form is taken into a tube called the alimentary canal where it is digested and absorded into the body.
Saprotrophic nutrition
Is the method by which  fungi and many prokaryotes feed. They live and grow on their substance , which can be anything organic, such as milk bread  or dead body .They secrete enzymes from their bodies, and digest the food material around them before absorbing it.
Parasitic nutrition
Is the method of feeding which has evolved in many different groups of organisms, including various kinds of worms and fungi and a few plants. Parasites fed on, and live in close association with, a living organism of a different species, called their host. They  can feed either holozoically biting their host or sucking fluids from it, or they can feed saprotrophically ,absorbing soluble food into their bodies.
                 Holozoic nutrition-feeding in humans:
Humans like all other animals are heterotrophs .This means that we need to eat food containing organic molecules. These organic molecules includes carbohydrates, fats and proteins. This all are our only source of energy. In contrast autotrophs   such as green plants do not need to take in any organic molecules at all. They obtain their energy from sunlight, and can use their energy to built organic molecules from inorganic one. They produce carbohydrates from carbon dioxide and water, by photosynthesis and can them use these carbohydrates, plus inorganic ions such as nitrate, phosphate and magnesium , to manufacture  all the organic molecules that they require .Heterotrophs therefore depend on autotrophs  for the supply of organic molecules on which they feed. Some of them feed directly on plants, while others feed further along a food chain. But eventually all of our food can be traced back to green plants, and the energy of sunlight.
             The structure of the human alimentary canal:
The alimentary canal is a long hollow tube which runs from the mouth to the anus .Together with several other organs, including the liver and the pancreas, it makes up the digestive system.
The total length of the human alimentary canal is between 5 and 6 m, from anus to mouth. To fit this considerable length into body, parts of the canal are folded and coiled inside the abdomen .The mucus is a substance secreted along the tube by cells lining its walls .Mucus helps food to slide through the canal without doing too much damage to the lining. It also forms a protective covering which keeps the digestive juices, which are inside the lumen of the canal, from coming into contact with the living cells of the walls. Along the whole length of  the alimentary canal there are muscles in the walls. These produce waves, of
Contraction and relaxation called peristaltic waves, which move food along the alimentary canal and help to mix the contents. Each region of the alimentary canal has it own function and different structure. There are 4 basic layers in the wall of the alimentary canal. Working from the inside these are: a) the mucosa b) the submucosa c) the muscularis externa d) the serosa. Many of this names came from Latin origin.
The mucosa is made up of 3 layers. The innermost layer is the epithelium. The structure of the epithelium varies in different parts   of   








the alimentary canal, but it always contains cells which secrete mucus.
Beneath it is a layer of connective tissue called lamina propria, which means ‘closest layer’. And beneath that is a layer of smooth muscle called the muscular is mucosa.
The sub mucosa is made up of areole connective tissue. This is an open-textured stretchy tissue, containing many elastic fibred and collagen fibres. Running through  it are numerous blood vessels and nerves.
The muscularis externa ia made of two  layers of muscle. The innermost layer has fibres running around the tube, and is called circular muscle. The outermost layer has fibres running along the tube and it is called longitudinal muscle.
The serosa is a very thin layer, made up of connective tissue covered with a single layer of thin, smooth closely fitting cells.

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