Saturday, July 14, 2012

Microorganisms: Friend and Foe : Solved Test Paper class 8

1.Fill in the blanks :
(1) Microorganisms can be seen with the help of a .......................... .
(2) Blue green algae fix .......................... directly from air to enhance fertility of soil.
(3) Alcohol is produced with the help of .......................... .
(4) Cholera is caused by a .......................... .
(5) Coci bacteria are ...................... in shape

(1) microscope.
(2) nitrogen
(4) bacteria.
(5) round.

Q.What are microorganisms ?

Ans. The living organisms aound us which we normally cannot see. These are called microorganisms or microbes.

Q.Into how many groups are microorganisms classified ?

Ans. Microorganisms are classified into four major groups. These groups are bacteria, fungi, protozoa and some algae. But viruses are also microscopic.

Q. Viruses are considered as being on the border line between living and non-living organisms,Why?

Ans: Viruses is nonliving out side living cells but grows and multiplies inside living cell so,viruses are considered as being on the border line between living and non-living organisms.The study of viruses is called Virology.
Virus was discovered by Ivanowsky, a Russian Botanist in 1892.

Q.What is bacteria explain?

Ans: Bacteria are unicellular and microscopic.The study of bacteria is called Bacteriology.
Bacteria were first observed under a microscope by the Dutch Scientist Anton VonLeeuwenhoek in 1675.
The bacterial cell is a  prokaryotic cell. It has a rigid cell wall protecting the cell and giving a definite
shape to it.

Four types of bacteria are recognized  based on shape. They are

1. Cocci (Spherical shaped)
2. Bacilli (Rod shaped)
3. Spirillum (Spiral or cork screw)
4. Vibrio (Comma Shaped)

On the basis of the number and arrangement of the flagella, bacteria are classified as

1. Monotrichous ( Single flagellum at one end)
2. Amphitrichous (Tuft of flagella arising at both ends).
3. Atrichous (Without any flagella).
4. Lophotrichous ( Tuft of flagella at one ends).
5. Peritrichous (Flagella all around). 

Questions: How do paramecium move and feed?
Ans: Paramecium swim in water by beating hair like structure called cilia against the water. The movement of cilia also direct food and water into gullet

Questions: Mention two ways in which fungi harm us?
Ans: Mould a kind of fungi spoil cooked food. Moulds and mildew grow on leather goods and cloths and furniture in monsoon and spoil them. Fungi cause diseases in plants and animals.

Questions: Mention three ways in which we use fungi?
Ans: Following are the three ways in which we use fungi

(i) Mushroom a kind of fungi eaten as a food.

(ii) Yeast is a kind of fungi used to prepare alcoholic drink, bakery product,

(iii) Penicillin and some other antibiotics are made from certain moulds

Questions: W hat does Sargasso Sea woe its name to?
Ans: Sargasso Sea woe its name to Sargassum, a particular sea weeds that grow abundantly in sea. Sailor avoids this sea as their boat stuck in the tangled mass of seaweeds.

Questions: What are the difference between the cell of bacteria and the cell of other living body?
Ans: The difference between the cell of bacteria and the cell of other living body are

(i) Cell wall is not made up of cell wall

(ii) Do not have nucleus

(iii)Does not have membrane bound organelles

Questions: Do red and brown algae have chlorophyll?
Ans: Yes, red and brown algae have pigment of colour which cover the colour of chlorophyll and make them appear red brown or yellowish

Questions: Name a protozoon which can photosynthesize?
Ans: Euglena contain chlorophyll and can photosynthesise, lack of cell wall

Questions: How do bacteria reproduce?
Ans: Bacteria reproduce by binary fission

Chapter: VIII Microorganisms-Friend and Foe
Microorganisms : Solved Questions   Read     Download 
Microorganisms-  : Notes                      Read     Download  
Microorganisms-  : MCQ 's                    Read     Download 

Microorganisms-  : Test Paper-1         Read     Download
Microorganisms-  : Test Paper -2       Read     Download 

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