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Chapter 9a

Economic Importance of Bacteria

Class 9 - Concise Biology Selina


Multiple Choice Type

Question 1

Bacteria are no more classified as plants primarily because:

  1. These are unicellular ✓
  2. These are microscopic
  3. Many of them are parasitic
  4. They have no chlorophyll

Question 2

A particular species of which one of the following, is the source bacterium of the antibiotic, discovered next to penicillin, for the treatment of tuberculosis?

  1. Escherichia
  2. Streptomyces ✓
  3. Rhizobium
  4. Nitrobacter

Question 3

Which bacteria is rod shaped?

  1. Coccus
  2. Spirillum
  3. Bacillus ✓
  4. Vibrio

Question 4

Which bacteria fixes nitrogen in the soil?

  1. Nitrobacter
  2. Nitrosomonas
  3. Rhizobium ✓
  4. Clostridium

Very Short Answer Type

Question 1

Name the three common types of bacteria.

Answer

The three common types of bacteria are as follows:

  1. Bacilli (rod-shaped bacteria)
  2. Cocci (spherical bacteria)
  3. Spirilla (twisted or spiral bacteria)

Question 2

Match the items in Column A with those in Column B

Column AColumn B
PenicilliumBacteria occurring in chains.
DiplococciAntibiotic.
StreptococciBacteria occurring in pairs.

Answer

Column AColumn B
PenicilliumAnibiotic.
DiplococciBacteria occurring in pairs.
StreptococciBacteria occurring in chains.

Short Answer Type

Question 1

Would you consider the bacteria and yeast as plants? Give reason.

Answer

We cannot consider bacteria and yeast as plants. The reasons for it are as given below:

  1. Bacteria belongs to the Kingdom Monera while yeast belong to Kingdom Fungi. Plants belong to Kingdom Plantae.
  2. The plant kingdom consists of the multicellular organisms while bacteria and yeast are unicellular.

Question 2

In what form bacteria may be present in the air?

Answer

In air, bacteria can be present in the form of spores.

Question 3

Why is spore formation in bacteria not considered a form of reproduction?

Answer

Spore formation in bacteria cannot be considered as a form of reproduction as they can reproduce through asexual means only such as cell division or fission. The formation of spores in bacteria is only an escape tactic from unfavorable condition that is exhibited by them.

Question 4

In what respect do you consider bacteria as simple organisms?

Answer

Bacteria are unicellular organisms that lack membrane bound cell organelles like chloroplast, mitochondria, etc. and even a well-defined nucleus is absent which states that they have a simpler cellular organization.

Question 5

State the differences between

  1. Decay and putrefaction.
  2. Pasteurization and sterilization of food/objects/equipments.

Answer

  1. Decay and Putrefaction.
DecayPutrefaction.
Complete breakdown of organic matter by bacteria.Incomplete breakdown of organic matter by bacteria.
Does not emit a foul smell.Emits a foul smell.
  1. Pasteurization and Sterilization
PasteurizationSterilization
Temperature - 60°CTemperature - 110°C
Does not kill sporesKills even spores
Partial sterilizationComplete sterilization
Example – Milk sterilizationExample – Canned food sterilization.

Question 6

Why is it generally advised that every living room in the house should get direct sunlight at least for a short time?

Answer

Direct sunlight contains ultraviolet radiations of the Sun, which help in killing of mould spores present in air. Hence, it is advised that every living room in the house should get direct sunlight at least for a short time.

Question 7

Would there be any bacteria in an aquarium?

Answer

Yes, bacteria can exist in aquarium. Bacteria can exist practically everywhere, as they can withstand any climatic condition.

Long Answer Type

Question 1

Both bacteria and yeast reproduce by asexual method, but how does this method differ in them?

Answer

Bacteria reproduce asexually by means of the binary fission, while yeast reproduces asexually by budding producing chains.

Question 2

Describe the role of micro-organisms in industrial production.

Answer

Role of micro-organisms in industrial production-

  1. Bacteria are used in coffee and tobacco processing and also to produce vinegar.
  2. Bacteria can be used to produce different flavours of coffee, tea etc.
  3. Leather tanning indirectly involves the action of some micro-organisms.
  4. Bacteria are also involved to make fibres that are used to make linen, rope etc. They are obtained by fibre loosening of flax and hemp by ratting.
  5. Bacteria can be used in the large scale production of antibiotics, hormones, vaccines etc.

Question 3

How do bacteria obtain their nourishment?

Answer

Most bacteria are heterotrophic i.e. they depend on readymade food from different sources. In this category, the bacteria maybe:

  1. Saprotrophic — Such bacteria draw nourishment from decaying dead organisms.
  2. Parasitic — Such bacteria draw nourishment from the body of their living hosts.

The bacteria secrete powerful enzymes from their cells into the surrounding food containing material. The enzymes make the food material soluble which is then absorbed as a solution into the bacterial cell.

Question 4

Describe any two uses of bacteria in industry.

Answer

Uses of bacteria in industry:

  1. Tanning of leather — It is brought about by sunlight with the involvement of a few bacteria which breakdown the soft perishable parts of the skin.
  2. Tea curing — Different flavours of tea are produced by certain bacteria.

Question 5

What are antibiotics? Name any two examples.

Answer

Antibiotics are chemical substances produced by a living organism which inhibits or kills the growth of micro-organisms that cause the diseases such as fungi and bacteria. Examples of antibiotics are:

  1. Streptomycin
  2. Penicillin

Question 6

Is tinned and sealed food always safe to eat? Give reasons in support of your answer.

Answer

No, tinned and sealed food are not always safe to eat as it may contain harmful bacteria like Clostridium botulinum that causes food poisoning. Clostridium botulinum releases toxins under low-oxygen conditions. These toxins are very lethal and can block nerve functions leading to muscular and respiratory paralysis.

Moreover, the chemicals used in the inner coating of the container can be harmful for humans.

Structured / Application / Skill Type

Question 1

Study the diagram given below and then answer the questions that follow:

Briefly describe how nitrogen of the atmosphere is converted to nitrates by leguminous plants. Economic Importance of Bacteria and Fungi, Concise Biology Solutions ICSE Class 9.

(a) Briefly describe how nitrogen of the atmosphere is converted to nitrates by leguminous plants.

(b) Name the bacteria that converts (i) Ammonium compounds to nitrites (ii) Nitrites to nitrates

(c) State how the nitrates in the soil get converted to nitrogen of the atmosphere.

(d) Role of plants and animals in the formation of ammonium compounds.

Answer

(a) Soil bacteria such as Rhizobium are present in the root nodules of leguminous plants. These bacteria convert free nitrogen of the soil to soluble nitrates.

(b) The names of the bacteria are as follows:
    (i) Ammonium compounds to nitrites — Nitrosomonas
    (ii) Nitrites to nitrates — Nitrobacter

(c) Denitrifying bacteria in the soil break down nitrates present in the soil to release nitrogen gas which enters the atmosphere.

(d) Soil contains nitrifying bacteria that are crucial in converting nitrogenous wastes of dead and decaying matter of plants and animals to ammonia. This ammonia is then converted to ammonium compounds. This is how animals and plants assist in forming ammonium compounds.

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