Q2 of 8 Page 189

Living organisms show a great degree of diversity in their size. A considerable number of species are not visible to naked eye. They can only be seen with the help of a microscope. How will you measure the size of micro organisms?

Due to very small size, some organisms are not visible to naked eye and can only be seen under a microscope. Such organisms are thus called microorganisms. To measure them, units such as micron (10^-6 m, or tenth lac fraction of one metre), or millimicron (10^-9) are used.


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1

Choose the best answer:

a) Algal bloom leads to loss of species diversity which is known as _______. (Eutrophication, Pasteurisation)


b) Which one of the following cause amoebic dysentery? (Entamoeba histolytica, Plasmodium vivax, Plasmodium falciparum)


c) Milk is heated to 72o C for 30 minutes and then suddenly cooled to12o C. Microbes are killed without causing damage to the taste and quality of milk. Name this process (dehydration, pasteurisation)


d) Nodules are responsible for nitrogen fixation. Name the bacteria present inside the root nodules. (Acetobactor, Rhizobium, Clostridium)

 3

Fungi do not possess chlorophyll. Hence, they are incapable of photosynthesis. So, they depend on either living organisms or non-living things. Name the two types of modes of nutrition in fungi.

 4

Communicable diseases are pathogenic diseases which are spread from person to person either directly or indirectly. Write the mode of transmission of the following diseases.

i) Cholera, typhoid


ii) Malaria

 5

The conversion of sugar solution into alcohol and liberation of carbon dioxide is known as fermentation. Which microorganism is responsible for this process?