CBSE NCERT Solutions for Class 8 Science Chapter 2

NCERT solutions are easy to understand and can help students to clear their doubts instantly. The solutions cover each chapter and exercise from the class 8 science book.

CBSE NCERT Solutions for Class 8 Science Chapter 2:


What are the major groups of microorganisms?


There are five major groups of micro-organisms:
i. Bacteria - They are single celled disease-causing micro-organisms. They can be
spiral or rod- shaped.
ii. Fungi - They are mostly multicellular disease-causing microbes. Bread moulds are
common examples of fungi.
iii. Protozoa - They mainly include organisms such as Amoeba, Plasmodium, etc. They can be unicellular or multicellular.
iv. Virus -Viruses are disease-causing microbes that reproduce only inside the host
v. Algae - They include multicellular, photosynthetic organisms such as
Spirogyra, etc.


Write 10 lines on the usefulness of microorganisms in our lives.


Micro-organisms are too small to be seen through naked eyes. However, they are
vital to plants and the environment.
i. Lactobacillus is used to form curd from milk.
ii. Rhizobium present in the roots of pulse plants fix nitrogen from air and supply
nitrogen compounds to the pulse plants.
iii. Micro-organisms are also used in winemaking, baking, pickling, and other food making processes.
iv. Alcoholic fermentation by yeast is widely used in the preparation of wine and
v. Microbes are used to reduce pollution. For example, decomposers such as bacteria and fungi break down dead bodies and excreta to form inorganic compounds, which can be absorbed by plants.
vi. Microbes also play an important role in the preparation of medicines. Antibiotics are chemicals produced by micro-organisms to kill bacteria. Penicillin is an antibiotic made from Penicillium.
vii. Bacteria present in our intestine helps in proper digestion and release Vitamin B which is absorbed by intestine.
viii. Many vaccines are prepared from micro-organisms. These vaccines are given to
children to protect them from disease.
ix. Certain microbes are also used in the biological treatment of sewage and industrial effluents.
x. Yeast is used in making idli, bhaturas, bread, pastries and cakes.


Can microorganisms be seen with the naked eye? If not, how can they be seen?


Microorganisms are too small to see them with naked eye. They can be seen
with the help of a magnifying glass or microscope.