Selina Concise Class 9 Biology Chapter 9 Economic Importance of Bacteria and Fungi Solution

Selina Concise Class 9 Biology Solution Chapter No. 9- ‘Economic Importance of Bacteria and Fungi’ For ICSE Board Students.

Exercise 1 Solution

A.)

1.)

Answer: d) they have no chlorophyll.

Most of the bacteria are not included in the plants because they are dependent on the food from different resources and do not have chlorophyll.

2.)

Answer: b) Streptomyces.

The next antibiotic ‘streptomycin’ was discovered by Selman Waksman which is source of bacterium ‘Streptomyces griseus’.

3.)

Answer: c) Bacillus.

The bacteria is divided into four types according to their shapes. The Bacillus bacteria is of rod-shaped bacteria.

4.)

Answer: c) Rhizobium.

The soil bacteria is Rhizobium. It is present in small nodules on the roots of leguminous plants. It pick up nitrogen from soil and converts into soluble nitrates.

B.)

1.)

Answer:

The three common types of bacteria are: Bacilli which is a rod-shaped bacteria, Cocci which is spherical bacteria and Vibrio which is comma-shaped bacteria.

2.)

Answer:

Column A Column B (Answers)
Penicillium b) Antibiotic
Diplococci c) Bacteria occurring in pairs
Streptococci a)Bacteria occurring in chains

 C.)

1.)

Answer:

Plants have some features which includes them in this category. Plants have chlorophyll and they produce their own food by photosynthesis. Their mode of nutrition is different from bacteria and yeast. Bacteria and yeast don’t have chlorophyll pigment and they are saprotrophic, sometimes parasitic. So, bacteria and yeast are not plants.

2.)

Answer:

The bacteria which are present in the air are in the form of spores. This can be carried far by wind or water.

3.)

Answer:

The spore formation is a method of escaping unfavourable condition. The reproduction in bacteria occurs asexually by cell division. Hence, spore formation in bacteria is not considered a form of reproduction.

4.)

Answer:

The bacterium cell is simple and bacteria is simple organisms because the nucleus in bacteria is not well defined. But, bacteria have central region where chromatin (DNA) is present. And it does not contain membrane bound organelles.

5.)

Answer:

a)

Decay Putrefaction
The complete breakdown of organic matter with the help of bacteria occurs in Decay. The incomplete breakdown of organic matter with the help of bacteria occurs in Putrefaction.

 b)

Pasteurization Sterilization
After boiling at 60° C temperature, it does not kill spores. After boiling at 110° C temperature, it kills spores.

 6.)

Answer:

The ultraviolet radiations of sunlight helps to kill spores and moulds which are present in the air. If a place is not getting direct sunlight then the formation of bacteria will occur. So, direct sunlight is advised for the house.

 7.)

Answer:

The Nitrobacter and Nitrosomonas are the bacteria that are present in the aquarium. So, there is presence of bacteria in the aquarium.

 D.)

1.)

Answer:

By the fission or cell division the bacteria reproduce asexually. In the beginning of the reproduction, the circular DNA duplicates and cell expands. Because of this expansion, two DNA gets separated on two sides.

The separation of the two daughter cell is depends on the type of bacteria. In some bacteria, two daughter cell will remain attached or they can separate. The separated cells will be independent cells.

 2.)

Answer:

Role of micro-organisms in industrial production are as follows:

i) Certain bacteria are useful in the production of different flavours of tea. This is called as tea curing.

ii) Some bacteria are involved in the leather tanning.

iii) Bacteria are useful in the productions of antibiotics, serums and vaccines.

iv) Bacteria are also helpful in agriculture field. The nitrogen fixing bacteria play important role.

3.)

Answer:

The bacteria are able to obtain their nourishment by two ways are as follows:

i) Saprotrophic- Some bacteria have saprotrophic mode of nutrition. In the saprotrophic, bacteria obtain nourishment from decaying dead organisms.

ii) Parasitic- Some bacteria have parasitic mode of nutrition. In this mode of nutrition, bacteria obtain nourishment from the body of their living hosts.

4.)

Answer:

  1. Tea curing
  2. Tanning of leather

Refer Que. 2 Answer.

5.)

Answer:

Antibiotic: It is a chemical substance which is produced by the living organisms where it can stop the growth of some disease-causing bacteria and fungi.

Examples of antibiotics are:

i) Penicillin

ii) Streptomycin

iii) Chloromycetin

6.)

Answer:

Spoilage of food mainly occurs by bacteria especially in summer. Tinned and sealed food is not safe for eating because it carries bacteria. Unsafe food can cause food-poisoning. Due to the tinned and sealed food, serious disease can cause like Botulism.

A special bacterium is responsible for Botulism. The affects will end with gas.

E.)

1.)

a)

Answer:

Rhizobium is a soil bacteria which found living in the small nodules of roots of leguminous plants such as beans. The nitrogen is picked up by the bacteria and bacteria converts it into soluble nitrate. Bacteria converts nitrogenous waste of animals and dead remains of plants and animals into ammonia. And then ammonia is converted into ammonium compounds.

The bacteria Nitrosomonas converts ammonium compound into nitrites. Nitrobacter then converts nitrites into nitrate which is the end step of nitrification.

b)

Answer:

i) Nitrosomonas

ii) Nitrobacter

c)

Answer:

The nitrates are broken down by the denitrifying bacteria which are present in the soil. They release nitrogen gas that later enters atmosphere.

d)

Answer:

Some bacteria converts nitrogen wastes of animals and the dead remains of plants and animals into ammonia and later it gets converted into ammonium compound. The plants and animals are responsible for the formation of ammonium compound.

Exercise 2 Solution:

A.)

1.)

Answer: b) Yeast

By killing yeast cells, the ethanol or ethyl alcohol is produced and starts at concentration.

2.)

Answer: c) Spore formation

The spores will germinate in warmth and moisture condition. Hence, spore formation occurs in all fungi but not in all bacteria.

3.)

Answer: d) they do not have a true nucleus

The prokaryotic organisms don’t have well defined nucleus. The bacteria don’t have true nucleus so they are referred as prokaryotes.

4.)

Answer: a) Ethyl alcohol

The production of ethyl alcohol occurs at a concentration of about 12% by killing yeast cells.

B.)

1.)

a)

b) Correct

c)

d) Correct

C.)

1.)

Answer:

The mould Rhizopus is most common mould which mainly found on bread mould. It also grow on various organic matter like fruits, animal dung and leather goods in warm and humid climate.

2.)

Answer:

The ultraviolet radiations of sunlight helps to kill spores and moulds which are present in the air. If a place is not getting direct sunlight then the formation of moulds of fungus will occur. So, direct sunlight is advised for the house.

3.)

Answer:

The role of certain fungi in industrial area are as follows:

  1. Fungi are useful in wine production which is an alcoholic beverage.
  2. Fungi are also useful in bread baking which is also called as baking.
  3. They are helpful in the production of antibiotics.
  4. They are used in the production of alcohol.
  5. Useful in Cheese making
  6. Helpful in the preparation of organic acids.

4.)

Answer:

Useful effects of wine includes:

i) It can be a stimulant if in mild quantity.

ii) It can reduce anxiety and helps in digestion.

Harmful effects of wine includes:

i) If a person is alcoholic then can develop body ailments, particularly liver cirrhosis.

ii) It can cause high blood pressure, if takes in large quantity.

5.)

Answer:

a)

Saprophyte Parasite
Saprophytic organisms obtain nourishment from dead organic matter. Parasitic organism can obtain their nourishment from body of the living hosts.

 b)

Aerobic respiration Anaerobic respiration
The products of aerobic respiration are CO2, Water, and ATP. The products of Anaerobic respiration are Ethanol, CO2, and Energy.

D.)

1.)

Answer:

Antibiotic: It is a chemical substance which is produced by the living organisms where it can stop the growth of some disease-causing bacteria and fungi.

Examples of antibiotics are:

i) Penicillin

ii) Streptomycin

iii) Chloromycetin

2.)

Answer:

Spoilage of food mainly occurs by bacteria especially in summer. Tinned and sealed food is not safe for eating because it carries bacteria. Unsafe food can cause food-poisoning. Due to the tinned and sealed food, serious disease can cause like Botulism.

A special bacterium is responsible for Botulism. The affects will end with gas.

3.)

Answer:

The Nitrobacter and Nitrosomonas are the bacteria that are present in the aquarium. So, there is presence of bacteria in the aquarium.

E.)

1.)

a)

Answer:

The moulds get inside the bell-jar because moulds are already present in air, water etc. or everywhere.

b)

Answer:

The mould will occur on bread but, it can occur after some time. In humid and warm condition, production of mould increases rapidly.

c)

Answer:

If the moist bread is kept below freezing point then the mould will not grow on bread.

d)

Answer:

The spores or mycelia will grow firstly on the bread.

e)

Answer:

The mode of nourishment in bread mould is of saprophytic type. It obtains nourishment from the substratum and it grows on substratum.

2.)

Answer:

Five steps in edible mushroom cultivation are as follows:

i) Composting- Wheat or paddy straw, chicken manure and some organic and inorganic fertilizers mixture forms compost and is kept at 50° C for one week.

ii) Spawning- Mycelium have mushroom seed which is introduced to compost and kept it for couple of days.

iii) Casting- Formation of thin soil layer on compost is an essential step. It provides support to the mushroom, humidity and regulates temperature.

iv) Cropping and harvesting – Mycelium grows between 2 to 6 weeks and fully grown mushroom taken out.

v) Preservation- vacuum cooling, gamma radiation and freeze drying are some of methods of preservation.

3.)

a)

Answer:

The denitrifying bacteria are responsible for the supply of nitrate to the plants. Large amount of nitrates to the plant is harmful for the ecosystem. Therefore, denitrifying bacteria are blessing as well as curse to farmers.

b)

Answer:

The yeast is used in dough and it makes dough to rise when baked. It gives bubble or spongy texture to the bread. So, yeast is used in bakeries and breweries.

Updated: August 24, 2021 — 11:49 am

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