Term Paper on the Types of Nutrition | Organisms | Biology

Here is a term paper on the autotrophic and heterotrophic types of nutrition in organisms.

Term Paper on the Types of Nutrition

Term Paper # 1. Autotrophic Nutrition:

In autotrophic nutrition, an organism makes its own food from simple raw materials. Carbon and energy requirements of the autotrophic organism are fulfilled by photosynthesis.

Photosynthesis- Green plants, which are autotrophic, synthesize food through the process of photosynthesis. Photosynthesis is a process by which green plants, having chlorophyll, synthesize the simple sugar (glucose) from the simple raw materials, water and carbon dioxide using the energy of sunlight. Oxygen is released in this process.

The overall equation of photosynthesis is:

All green parts of a plant are capable of performing photosynthesis, the leaves photosynthesize the most. The cells of the leaves contain special organelles called chloroplasts, which are the main sites of photosynthesis. These are plastids which contain the light-absorbing green pigment chlorophyll.

The chloroplasts in leaves contain closely packed flattened sacs, called thylakoids, arranged in piles, called granum. Granum lies in a colourless ground substance, called stroma. Thylakoids contain green pigments, called chlorophyll, which trap solar energy.

Carbon Dioxide is inhaled by stomata. Stomata are tiny pores present on the surface of the leaves. Massive amounts of gaseous exchange takes place in the leaves through these pores for the purpose of photosynthesis.

However exchange of gases occurs across the surface of stems, roots and leaves as well via stomata. Since large amounts of water can also be lost through these stomata, the plant closes these pores when it does not need carbon dioxide for photosynthesis.

The opening and closing of the pore is regulated by guard cells. The guard cells swell when water flows into them, causing the stomatal pore to open. Similarly, the pore closes if the guard cells shrink.

Water required for photosynthesis is absorbed from the soil by the roots in terrestrial plants. Other materials like nitrogen, phosphorus, iron and magnesium are mixed in water in the soil.

Nitrogen is an essential element used in the synthesis of proteins and other compounds which is taken up in the form of inorganic nitrates or nitrites, or it is taken up as organic compounds which have been prepared by bacteria from atmospheric nitrogen.

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Term Paper # 2. Heterotrophic Nutrition:

The word ‘heterotroph’ is derived from two Greek words—hetero (other) and trophe (nutrition). Heterotrophic organisms obtain food from other organisms. Thus, they are also called as consumers. All animals and non-green plants like fungi come under this category.

All organisms are not capable of eating complete food and breaking it inside the body like multicellular animals. Hence, fungi like bread mold, yeast and mushrooms break down food outside and absorb nutrients decaying food.

Some other organisms derive nutrition from plants or animals without killing them. This parasitic nutritive strategy is used by a wide variety of organisms like cuscuta (amar-bel), orchids, ticks, lice, leeches and tape-worms.

The Nutrition in unicellular organisms like Amoeba and Paramecium is Holozoic.

Amoeba:

Amoeba takes in food using temporary finger-like extensions of the cell surface which fuse over the food particle forming a food-vacuole. Inside the food vacuole, complex substances are broken down into simpler ones which then diffuse into the cytoplasm. The remaining undigested material is moved to the surface of the cell and excreted.

Paramecium:

In Paramecium, the cell has a definite shape and food is taken in from a specific spot. Cilia which cover the entire cell surface move the food to the entry spot. The food in the food vacuoles of the Amoeba and Paramecium is digested by lytic enzymes.

Nutrition in Human Being:

Humans eat food that has many complex materials to be broken down filtered and separated in the body for proper use. The process of breaking down complex molecules into simple molecules is called digestion. The digestive system is made of the alimentary canal or digestive tract, which is a long tube and runs from the mouth (where food enters) to anus (where indigestible waste leaves).

The mouth, buccal cavity, pharynx, oesophagus, stomach, intestine, rectum and anus are parts of the alimentary canal. The digestive glands are the salivary glands, the gastric glands, the liver, the pancreas and the intestinal glands.

The journey of food in the digestive system is as follows:

i. Mastication:

Digestion begins in the mouth. A brain reflex triggers the flow of saliva into the mouth when we see or think about food. Saliva moistens the food while teeth chew it up and make it easier to swallow. Saliva contains an enzyme named amylase that breaks down starch in the food into simple sugars.

ii. Pharynx:

The muscles in the tongue and the mouth help in swallowing the food. The food enters pharynx, which is a passage for food and air. A small flap of skin, called epiglottis, closes over the pharynx preventing the food from entering the trachea.

iii. Oesophagus:

The food moves down a muscular tube in the chest called as oesophagus. At the end of oesophagus, there is sphincter that allows the food into to the stomach, then closes back up so that the food does not travel back into the oesophagus. This is called as Oesophageal Sphincter.

iv. Stomach:

The stomach is a large organ that expands when food enters it. The muscular walls of the stomach help in mixing the food thoroughly with more digestive juices. In the stomach, food is mixed with the gastric juices secreted by the gastric glands, which contain chemicals like hydrochloric acid and enzymes like pepsin, rennin and lipase. The partially digested food in the stomach is acidic, and is known as chyme.

The hydrochloric acid creates an acidic medium that facilitates the action of the enzyme pepsin. The mucus protects the inner lining of the stomach from the action of the acid under normal conditions. The exit of food from the stomach is regulated by a sphincter muscle that releases it in small amounts into the small intestine.

v. Small Intestine:

The food now enters the small intestine. This is the longest part of the alimentary canal which is fitted into a compact space because of extensive coiling. The small intestine is the site of the complete digestion of carbohydrates, proteins and fats.

a. Liver:

The liver and pancreas secrete digestive juices into the small intestine. The food coming from the stomach is acidic and has to be made alkaline for the pancreatic enzymes to act. Bile juice from the liver accomplishes this in addition to acting on fats.

Fats are present in the intestine in the form of large globules which makes it difficult for enzymes to act on them. The bile salts break fats into smaller globules increasing the efficiency of enzyme action. This is similar to the emulsifying action of soaps on dirt.

b. Pancreas:

The pancreas secretes pancreatic juice that contains enzymes like trypsin for digesting proteins and lipase for breaking down emulsified fats.

The walls of the small intestine contain glands that secrete intestinal juice. The enzymes present in it finally convert the proteins to amino acids, complex carbohydrates into glucose and fats into fatty acids and glycerol. The digested food is taken up by the walls of the intestine.

vi. Villi:

Villi are finger-like structure supplied with blood vessels, which increase the surface area for the absorption of food and supply it to every cell of the body.

vii. Large Intestine:

The large Intestine is divided into cecum, colon and rectum. There are trillions of bacteria, yeast, parasites living in the intestine and mostly in the colon. Villi absorb the water from the undigested food, passed from the small intestine, which turns into solid waste. This solid waste is stored as excreta in the rectum.

viii. Anus:

The anus excretes the solid waste from the body. The exit of this waste material is regulated by the anal sphincter.

Illustration 1:

Absorption spectrum of chlorophyll is maximum in – light.

(a) Red

(b) Blue

(c) Yellow

(d) Blue-Violet

Sol:

We can see how different wavelengths of light affect photosynthesis by looking at action spectra. An action spectrum relates the rate of photosynthesis to the wavelength of light being received by a plant.

For green plants, including algae, the action spectrum shows that most photosynthetic activity takes place in blue-violet and orange-red lights since these are the colors that are mostly absorbed by the main chlorophylls and the carotenoids. Photosynthetic activity is lowest in green light since green light is hardly absorbed at all by these pigments.

The relative absorption of light of different wavelengths by pigments can be shown in absorption spectra. Action and absorption spectra correspond quite closely. Wavelengths of light which are more readily absorbed by photosynthetic pigments cause higher levels of photosynthesis. Option b is the answer.