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

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 4

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 5

Briefly describe the modes of reproduction in bacteria.

Accepted Answer

Bacteria reproduce by vegetative, sexual and asexual methods. Vegetative method includes budding, fragmentation and binary fission. In budding, the bud develops from the end of the cell. The bud enlarges and becomes daughter cell and gets separated from parent cell. In binary fission, parent cell divides into two daughter cells. Asexual reproduction include endospore, conidia and zoo spores formation. During unfavourable condition, endospores are formed. Under favourable condition, endospore wall gets ruptured and new cell is formed. Sexual reproduction include transformation, transduction and conjugation. These are the methods of genetic recombination.

Question 6

In Rhizopus, tubular thread-like structures bearing sporangia at their tips are called as

Accepted Answer

Rhizopus is a saprobic fungus which feeds on the dead decaying organic matter. Its body is made up of branching mycelia composed of three types of hyphae- rhizoids, stolons and unbranched sporangiophores. Rhizoids are root like hyphae that grow downward into the soil and help in absorption of water. A stolon is a special slender horizontal hyphae that help in the propagation of an organism. Sporangiophores are straight, unbranched tubular thread like hyphae which bear rounded sporangia at its tips. sporangia produce non-motile multinucleate spores for asexual reproduction. Thus, the correct answer is option B.

Question 7

What are (i) methanogens (ii) Halophiles (iii) thermoacidophiles?

Accepted Answer

(i) Methanogens: These are microorganisms that produce methane as a byproduct of metabolism in anoxic conditions. They belong to class Archaea.(ii) Halophiles: These are microorganisms that grow and thrive in high salt concentrations. (iii) Thermoacidophiles: These are microorganism that are both thermophilic and acidophilic, that is they can grow under conditions of high temperature and low pH.

Question 8

Which among the following is not a prokaryote?

Accepted Answer

An organism that does not possess a true nucleus (nucleus with nuclear membrane) and membrane-bounded organelles are called as prokaryotes.  Monerans are prokaryotes. Eg. bacteria (Mycobacterium), cyanobacteria (Nostoc and Oscillatoria).  Saccharomyces belong to Kingdom Fungi which possess a true nucleus and membrane-bounded organelles i.e., eukaryotic. Thus, the correct answer is option B.

Question 9

Which one of the following statements is wrong?

Accepted Answer

(A) Correct answer- D(B) Explanation of correct answer:Phycomycetes are also called algal fungi. They have characteristic aseptate coenocytic hyphae. Cyanobacteria are also called blue-green algae. They are photosynthetic bacteria. Golden algae are also called desmids. It is referred to as a single species, Prymnesium parvum.It is found in fresh water. Bacteria have two domains, namely eubacteria and archaea. Eubacteria are also called true bacteria. They have rigid cell walls and flagella.

Question 10

The odd one amongst following is

Accepted Answer

Nitrogen fixation can be done by either free-living organism or by forming a symbiotic association with plants. Free-living nitrogen fixers are Anabaena, Nostoc, Azotobacter, Clostridium, Aulosira, Bacillus species. While Rhizobium and Bacillus polymyxa forms a symbiotic association with roots to fix atmospheric nitrogen, pseudomonas is a denitrifying bacteria. Nitrococcus, Nitrobacter and Nitrosomonas are the nitrifying bacteria that convert ammonia to the usable form of nitrogen for plants. Thus, the correct answer is option B.

Archaebacteria

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Kingdom Monera

Kingdom Monera

Archaebacteria: A Deep Understanding

Kingdom Monera (Intermediate)

QUICK SUMMARY WITH STORIES

Introduction to Kingdom Monera

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.

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

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

Briefly describe the modes of reproduction in bacteria.

In Rhizopus, tubular thread-like structures bearing sporangia at their tips are called as

What are (i) methanogens (ii) Halophiles (iii) thermoacidophiles?

Which among the following is not a prokaryote?

Which one of the following statements is wrong?

The odd one amongst following is

Archaebacteria

Language

Rate

REVISE WITH CONCEPTS

Kingdom Monera

Kingdom Monera

Archaebacteria: A Deep Understanding

Kingdom Monera (Intermediate)

QUICK SUMMARY WITH STORIES

Introduction to Kingdom Monera

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.

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

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

Briefly describe the modes of reproduction in bacteria.

In Rhizopus, tubular thread-like structures bearing sporangia at their tips are called as

What are (i) methanogens (ii) Halophiles (iii) thermoacidophiles?

Which among the following is not a prokaryote?

Which one of the following statements is wrong?

The odd one amongst following is

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

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