CBSE Std 8 Biology Microorganisms : Their types-questions-answers-scandisk

Biology (CBSE)

Microorganisms : Their types

  • Scandisk (Question-answer)

1) True(T) or false(F)

a) All microorganisms form colonies.   F

b) The rod-shaped bacteria are called cocci.   F

c) Facultative bacteria can live either in the presence or absence of oxygen.    T

d) Yeast multiply by budding.    T

e) Diseases such as cold and cough are caused by bacteria.    F


2) Fill in the blanks.

a) Each mushroom consists of two parts, stalk and cap.

b) Bacteria that require oxygen for their growth are called aerobic bacteria.

c) Malaria is caused by a protozoan called Plasmodium.

d) The three types of fungi are yeast,mushroom and moulds.


3) Give one word for the following.

a) The process by which a parent cell divides into two equal daughter cells,each with nucleus. Binary fission

b) These germinate under suitable environment conditions to form new moulds. Spores

c) Formed as a result of a symbiotic association between fungi and photosynthetic algae. Lichens

d) These reproduce only inside the living cells of organisms. Virus


4) Name the four major groups of microbes.

  • Bacteria
  • Fungi
  • Algea
  • Protozoa
  • Virus

5) Name two types of micro organisms that undergo sporulation for reproduction.

  • Bacteria
  • Fungi (mushroom and mould )

6) Give any two salient features of yeasts.

  • They are small and unicellular
  • They are useful for the production of alcohol, wine ,bread etc.
7) Give one unique feature of protozoans.
  • They posses animal-like characteristics like heterotrophic mode of nutrition and locomotion

8) Define microbes.

Microbes are group of organisms that are too small to be visible to the naked eye.

9) Mentions the conditions necessary for the growth of microorganisms.

  • Oxygen : Aerobic microbes thrive in the presence of oxygen,but anaerobic bacteria are inhibited by its presence.
  • Temperature : Microbe have an optimum temperature range for growth.
  • Sunlight : Some autotrophs require sunlight,but many grow and survive well without it.
  • Moisture : Microbes grow and multiply easily under moist and humid conditions.
  • Nutrients : Microbes may produce energy by synthesizing their own food or may be dependent on another source for their energy needs.

10) How are bacteria present in the human intestine beneficial to human being ?

E . coli is a bacteria present in the human intestine. It thrives on food present in intestine and in turn releases vitamin B and K,which are useful to human beings.

11) With the help of diagram explain the process of binary fission in bacteria.

12) Draw a graphic organiser to show the classification of bacteria on the basis of their shape and oxygen requirement.

13) What are moulds made up of? How do they multiply?

Moulds are made up of hyphae and spore.They multiply by sporulation.

  • steps of multiplication in moulds
  1. spore sacs containing spores develop at the tips of hyphae
  2. spore sacs burst open to release spores
  3. spores germinate under suitable environmental conditions to form new mould


14) How does budding take place in yeasts?

  • small bud develops on the body of the yeast
  • bud pinches off,thus giving to new yeast cell
  • can remain attached to the parent cell,forming a chain of yeast cells
15) Give any four salient features of protozoans.
  • It possess animal-like characteristics like heterotrphic mode of nutrition and locomotion
  • Found in most of aquatic environments from potholes to oceans,and in moist soil.
  • Act as herbivores, predators,decomposers and parasites in nature.
  • Reproduce by asexual and sexual mode of reproduction.

16) Which microbes would grow easily on a leather bag left under moist conditions?why?

  • Fungi(mould) would grow easily on a leather bag left under moist conditions because they are present in the air and it requires high humidity.

17) The decomposition of dead and decaying matter is essential for human beings. why?

  • To get nutrients from dead bodies for soil.
  • If there is no composers then dead bodies will pile up.
  • Plants can’t grow well without natural nutrients and so food chain will be disturb.
  • There is no breakdown of food.
  • As we can’t bury dead bodies,we have to burn them. so air will be more polluted.

18) What do you think would happen if all algal forms were wiped out from the oceans?

If all algal forms wiped out from the oceans,ocean food webs would completely collapse because algae is the main driver of photosynthesis.It provides significant oxygen.If algae were removed many organisms died.The more oxygen is used up for decomposition of these dead organisms. This would lead to even less oxygen to remaining species.

19) What are bacteriophages?

A virus that invades bacteria is called a bacteriophage.

20) Why does curd set well in summers as compared to winters?

Lactobacillus bacteria in changes milk into curd. These bacteria activated and multiply at 30-40 degrees centigrade temperature. In summer this temperature acquires perfectly so curd set well in summer as compared to winters.

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