Question 1

A bacterium divides every $35$ minutes. If a culture containing $10^5$ cells$/$ml is grown in $175$ minutes, what will be cell concentration after that period

Accepted Answer

It is given that a bacterium divides every 35 minutes. At 0 minutes, the culture contains 10$^5$ cells/mlAfter 35 minutes, the culture will contain 2$^1$ x 10$^5$ cells /mlSimilarly, after 175 minutes, that is after 5 generations, the number of cells will be 2$^5$ x 10$^5$ cells/mlThis is equal to 32 x 10$^5$ cells/mlThus, the correct answer is '32 x 10$^5$.'

Question 2

Explain with examples types of asexual reproduction in unicellular organism.

Accepted Answer

Different types of asexual reproduction in unicellular organisms are;Binary Fission - In binary fission, the parent cell divides either transversely or longitudinally into two equal halves called daughter cells. For example, Amoeba divides transversely and Leishmania divides longitudinally.Multiple Fission - In multiple fission, the parent cell divides into multiple daughter cells at same time. For example, Sporozoans.Budding - In budding, organisms develop bud in their body surface which later develops into a separate individual. For example, Budding Yeast.

Question 3

Archaebacteria differ from eubacteria in

Accepted Answer

Archaebacteria generally have the same shape, size, nutrition and appearance as bacteria. They multiply by means of binary fission.However, archaebacteria cell walls do not contain peptidoglycan. They also have different membrane lipid bond as compared to the bacteria and eukarya. Archea membrane lipids have ether bonds whereas bacteria has ester-linked lipids.Thus, the correct answer is option A.

Question 4

.Describe in brief the economic importance of bacteria.

Accepted Answer

The economic importance of a bacteria which is prokaryote and microscopic organism is: 1. Beneficial effects of Bacteria: A)  Role in agriculture a)   Bacteria as Scavenging: Saprophytic bacteria obtain food from organic remains such as animal excreta, fallen leaves, meat etc. They decompose these substances by the action of digestive enzymes aerobically or anaerobically (known as fermentation). Thus they help in sanitation of nature, so also known as scavengers. E.g. Pseudomonas) Nitrification: Rhizobium bacteria, living in root nodules of leguminous plant symbiotically, helps in fixing atmospheric nitrogen. Similarly, Nitrosomonas and Nitrococcus convert ammonium salt to nitrites. Nitrites are further changed to nitrates by Nitrobacter and Nitrocystis. It enables plants to uptake nitrogen. c) Production of Organic Manure: As stated above, saprophytic bacteria help in breaking of the complex organic substance to simpler forms. Thus, in this process, they help to convert farm refuse, dung and other wastes to manure. d) Preparation of Ensilage: Ensilage is preserved cattle fodder prepared by packing freshly chopped fodder sprinkled with molasses. Fermentation activity of bacteria produces lactic acid that acts as a preservative in ensilage.e) Production of fuel: Bacteria, while converting animal dung and other organic wastes to manure, help in the production of fuel that is a must in gobar gas plant.f) Disposal of sewage: Bacteria help in disposal of sewage by decomposing it and thus, help in environmental sanitation.B) Bacteria role in Industry a) Dairy Industry: Bacteria such as Streptococcus lactis convert milk sugar lactose into lactic acid that coagulates casein (milk protein). Then, milk is converted into curd, yogurt, cheese etc needed for the industry.b) Production of Organic Compounds: Fermentation (breakdown of carbohydrate in absence of oxygen) action of various bacteria produces organic compounds like lactic acid (by Lactobacillus), acetic acid (by Acetobacter aceti), acetone (by Clostridium acetabutylicum) etc.c) Fibre Retting: The action of some bacteria like Clostridium,Pseudomonas etc. help in fiber retting i.e. separation of stem and leaf fiber of plants from other softer tissue.d) Curing: The leaves of tea and tobacco, beans of coffee and cocoa are cured off their bitterness with the help of action of certain bacteria such as Bacillus megatherium.e) Production of Antibiotics: Number of antibacterial and antifungal antibiotics such as Hamycin, Polymyxin, Trichomycin etc are obtained from mycelia bacteria (like Streptomyces). Similarly, Bacillus is used for the production of antibiotics such as Bacitracin, Gramicidin etcf)  Production of Vitamins: Different kinds of vitamins are produced from bacteria like Riboflavin from Clostridium butylicum, Vitamin B12 from Bacillus megatherium and Vitamin K and B-complex from Escherichia coli.2. Harmful effects of Bacteria: Though bacteria play important role in agriculture, industries and natural sanitation etc, it has the following harmful effects: a) Food Spoiling: Saprophytic bacteria always not only help in decomposition of dead matters, but they also cause the rotting of vegetables, fruits, meat, bread etc.b) Food Poisoning: Bacteria like Staphylococcus aureus cause food poisoning and cause people diarrhea and vomiting.c) Damaging domestic articles: Spirochete cytophaga deteriorates cotton, leather, and wooden articles.d) Denitrification: Bacteria such as Thiobacillus and Microbacillusconvert nitrate of the soil to the gaseous nitrogen. This hampers plants very much.e) Desulphurization: Bacteria such as Desulfovibrio convert soil sulfates into hydrogen sulfide.f) Cause of Diseases: It is known that over 90% of human diseases and over 10% of plant diseases are caused by bacteria.

Question 5

Every 20 minutes, one bacterium divides into two. How many bacteria will be produced after two hours, if one starts with 10 bacteria?

Accepted Answer

According to the question, in a 20 minutes cycle, cells double. In 2 hours i.e 120 minutes there will be 6 cycles of 20 min each. If we start from 10 bacteria, then after 6 cycles of 20 minutes each (2 hours in total), we will have 10x 2^6 cells after 2 hours.So, the correct answer is '2^6 x 10'.

Question 6

Which one of the following is an incorrect statement regarding mycoplasma?

Accepted Answer

The Mycoplasma are organisms that completely lack a cell wall. They are the smallest living cells known and can survive without oxygen. Many mycoplasmas are pathogenic in animals and plants.So the correct option is &#34;They cannot survive without oxygen&#34;.

Question 7

Archaebacteria are able to survive in harsh habitats.

Accepted Answer

Presence of peptidoglycan in cell wall help archaebacteria to survive in extreme conditions.

Question 8

Describe the general characteristics of Kingdom Monera.

Accepted Answer

As per R H Whittaker's five kingdom classification, all the prokaryotic organisms (bacteria, blue-green algae) are placed under the Kindom Monera.The general characteristics of Kingdom Monera include;All are primitive prokaryotic organisms.They are generally unicellular.A membrane-bound nucleus is absent. Double-stranded DNA is suspended in the cytoplasm, known as a nucleoid.Membrane-bound organelles like mitochondria, endoplasmic reticulum, etc. are absent.Lives in anaerobic or aerobic conditions. They also survive in extreme climatic conditions like hot springs, snow, and deep oceans.They have 70S ribosomes.Most organisms have a rigid cell wall made of peptidoglycan. But, some organisms like mycoplasma even lack a cell wall.They have different modes of nutrition -  autotrophic (photoautotrophs or chemoautotrophs), heterotrophic, parasitic, saprophytic, symbiotic, etc.Reproduction is mainly asexual through binary fission or budding. Some modes of sexual reproduction like conjugation also exist.They may be motile (using flagella) or non-motile.

Question 9

Select the correct matches.(a) Nitrosomonas - nitrite to nitrate(b) Thiobacillus - denitrification(c) Nostoc - free-living nitrogen fixer(d) Azotobacter - anaerobic nitrogen fixer

Accepted Answer

Nitrification is a process in which ammonia is converted to nitrites and nitrites into nitrates. Examples of nitrifying bacteria includes Nitrosomonas, Nitrosococcus, Nitrobacter, Nitrococcus. Nitrosomonas, Nitrosococcus converts ammonia to nitrites. Nitrobacter, Nitrococcus converts nitrites to nitrates. Denitrification is a process by which nitrate is reduced to molecular nitrogen. Examples of bacteria that carry out denitrification process includes Thiobacillus. Nitrogen fixation is a process by which atmospheric nitrogen is converted into ammonium compounds. Example of free living nitrogen fixer includes Nostoc. Example of free living aerobic nitrogen fixer includes Azotobacter. Thus, the correct answer is 'b and c.'

Question 10

Choose the incorrect statement from the following.

Accepted Answer

The kingdom monera is comprised of the prokaryotic organisms. The kingdom is divided into two groups, archaebacteria and eubacteria. They are unicellular or multicellular forming filamentous structures. They do not have well-developed cell organelles such as the nuclear membrane, cell wall, nucleus, mitochondria, etc. Thus, the correct answer is option D.

Types of Archaebacteria

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REVISE WITH CONCEPTS

Archaebacteria

A bacterium divides every $35$ minutes. If a culture containing $1 0^{5}$ cells $/$ ml is grown in $175$ minutes, what will be cell concentration after that period

Explain with examples types of asexual reproduction in unicellular organism.

Archaebacteria differ from eubacteria in

Short / Long answer type questions.
Describe in brief the economic importance of bacteria.

Every 20 minutes, one bacterium divides into two. How many bacteria will be produced after two hours, if one starts with 10 bacteria?

Which one of the following is an incorrect statement regarding mycoplasma?

Archaebacteria are able to survive in harsh habitats.

Presence of peptidoglycan in cell wall help archaebacteria to survive in extreme conditions.

Archaebacteria are able to survive in harsh habitats.

Describe the general characteristics of Kingdom Monera.

Select the correct matches.
(a) Nitrosomonas - nitrite to nitrate
(b) Thiobacillus - denitrification
(c) Nostoc - free-living nitrogen fixer
(d) Azotobacter - anaerobic nitrogen fixer

Choose the incorrect statement from the following.

Types of Archaebacteria

Language

Rate

REVISE WITH CONCEPTS

Archaebacteria

A bacterium divides every 35 minutes. If a culture containing 105 cells/ml is grown in 175 minutes, what will be cell concentration after that period

Explain with examples types of asexual reproduction in unicellular organism.

Archaebacteria differ from eubacteria in

Short / Long answer type questions. Describe in brief the economic importance of bacteria.

Every 20 minutes, one bacterium divides into two. How many bacteria will be produced after two hours, if one starts with 10 bacteria?

Which one of the following is an incorrect statement regarding mycoplasma?

Archaebacteria are able to survive in harsh habitats.

Presence of peptidoglycan in cell wall help archaebacteria to survive in extreme conditions.

Archaebacteria are able to survive in harsh habitats.

Describe the general characteristics of Kingdom Monera.

Select the correct matches. (a) Nitrosomonas - nitrite to nitrate (b) Thiobacillus - denitrification (c) Nostoc - free-living nitrogen fixer (d) Azotobacter - anaerobic nitrogen fixer

Choose the incorrect statement from the following.

A bacterium divides every $35$ minutes. If a culture containing $1 0^{5}$ cells $/$ ml is grown in $175$ minutes, what will be cell concentration after that period

Short / Long answer type questions.
Describe in brief the economic importance of bacteria.

Select the correct matches.
(a) Nitrosomonas - nitrite to nitrate
(b) Thiobacillus - denitrification
(c) Nostoc - free-living nitrogen fixer
(d) Azotobacter - anaerobic nitrogen fixer