8th Class Science Cell - Structure and Functions Microorganisms

     Microorganisms

A microorganism or microbe are the living organisms, which are too small to be visible to the naked eyes. The study of microorganisms is called microbiology. The microorganism are bacteria, fungi, etc. However, viruses and prions are not microorganisms, they are classified as nonliving. They are found everywhere on the earth, including water, air and land. They are also called extermophiles. They act as a decomposer, and help in nutrient recycling in ecosystem. Pathogenic or harmful microbes can invade other organisms and cause disease.

           Useful Microbes

There are some microorganisms, which are useful to us; where as some of them are harmful. The useful microorganisms feed on the things that were once living. The decayed materials get mixed with the soil and provide essential nutrients for plants to grow. Such organisms are called decomposers. Without decomposers, the soil would not have got the nutrients, and would have run out of it. They are the natural recyclers of living things on earth.  

            Harmful Microbes

Some microbes can cause illness or disease, such as, chickenpox, mumps and measles. These are infectious diseases. Some microbes can cause food decay. For example, moldy bread or fruit, sour milk and rotten meat etc. If we take these rotten food, it can cause stomach upset and many other health problems.

       Haden prepared soup for himself. Due to some urgent work, he could not take the soup and went to his office. When he returned next day from his office, he found that the soup was spoiled and emitting bad smell. Which one of the following microorganism had spoiled the soup?

(a) Bacteria

(b) Virus

(c) Fungus

(d) Plasmodium

(e) None of these

Answer: (a)

Explanation

The microorganism which spoils the liquid food is bacteria.

      The microorganisms, which are found everywhere on the earth i.e. on the land, water, and air are called:

(a) Extermophiles

(b) Prions           

(c) Pathogens

(d) Moulds

(e) None of these

Answer: (a)

Explanation

Extermophiles are the microorganisms, which are found everywhere on the earth.

                Difference between Plant Cell and Animal Cell

• The biological electron transfer reactions leading to the production of ATP molecules.
• The most primitive and earliest forms of life forms on the earth are prokaryotic single celled organisms.
• The specific function within the cell is carried out by certain structure called organelles.
• The life spans of cell within the human body are different. It varies from few days to years.
• The self destruction of cell, when it undergoes infection or get damaged is called apoptosis.

• The essential part of maintenance of life process is nutrition, respiration, transportation of materials within the body, from one part to another.
• There are two mode of nutrition; autotrophic and heterotrophic.
• Heterotrophic are either consumer or decomposer.
• Human being have very complex digestive system, which digest the food.
• Respiration breaks down the complex food molecule into simplerform and release energy in the form of ATP.
• Respiration is of two types: aerobic and anaerobic.
• In human beings, the respiratory system is well defined and very complex.
• In plants, transportation takes place with the help of well defined tissue called xylem and phloem.
• In human, excretion of waste material takes place in the form of soluble nitrogen compounds, with the help of kidney.
• In plants excretion takes place in the form of gums, resins, falling of leaves, reaping of fruits etc..