Download App

Microbes in Human Welfare — BIOLOGY STD 12 Science — Question

Maharashtra BoardEnglish MediumSTD 12 ScienceBIOLOGYMicrobes in Human Welfare1 Mark
MCQ
Two statements are given-one labelled Assertion and the other labelled Reason. Select the correct answer to these questions from the codes $(a), (b), (c)$ and $(d)$ as given below.
Assertion: Azotobacter fixes nitrogen in symbiotic form.
Reason: Azotobacter form root nodules in the roots of leguminous plants.
  • A
    Both assertion and reason are true and reason is the correct explanation of assertion.
  • B
    Both assertion and reason are true but reason is not the correct explanation of assertion.
  • C
    Assertion is true but reason is false.
  • ✓
    Both assertion and reason are false.
✓

Answer

Correct option: D.
Both assertion and reason are false.

Azotobacter is a non-symbiotic nitrogen fixing bacteria that is it lives freely in the soil and perform nitrogen fixation. It is saprotrophic living on organic remains. Root nodules are formed by Rhizobium, a symbiotic nitrogen fixing bacteria.

Need a full question paper?

Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.

Start Generating Free

Explore more

More "Assertion (A) & Reason (B) MCQ" from Microbes in Human Welfare→Microbes in Human Welfare — all question types→BIOLOGY STD 12 Science question papers→Maharashtra Board STD 12 Science question papers→Maharashtra Board question paper generator→

Similar questions

For question two statements are given $-$ one labelled Assertion and the other labelled Reason. Select the correct answer to these questions from the codes $(a), (b), (c)$ and $(d)$ as given below.
Assertion : Biodiversity loss is now one of the world's most pressing crisis.
Reason : Lower diversity in a species leads to non $-$ uniformity.
→
For question, two statements are given$-$one labelled Assertion and the other labelled Reason. Select the correct answer to these questions from the codes $(a), (b), (c)$ and $(d)$ as given below.
Assertion: Core enzyme catalyses chain elongation of $\text{RNA}.$
Reason: The presence of sigma factor is required for initiation of transcription.
→
Read the following and answer any four questions from $(i)$ to $(v)$ given below:
The anther is a four$-$sided structure consisting of four microsporangia located at the corners, two in each lobe. $TI1e$ microsporangia develop further and become pollen sacs. In a transverse section, a typical microsporangium appears near circular in outline. It is generally surrounded by four wall layers$-$the epidermis, endothecium, middle layers and the tapetum.
  1. A dithecous another consists of $(A)$ microsporangia, $(B)$ in each lobe.
Select the option that correctly fills the blanks.
S. No
 $A$ $B$
$(a)$
Four
Two
$(b)$
Two
One
$(c)$
Two
Two
$(d)$
Four
One
  1. The given diagram shows microsporangium of a mature anther. Identify $A, B$ and $C.$
$(a)$
$A-$Middle layer
$B-$Endothecium
$C-$Tapetum
$(b)$
$A-$Endothecium
$B-$Tapetum
$C-$ Middle layer
$(c)$
$A-$Endothecium
$B-$Middle layer
$C-$Tapetum
$(d)$
$A-$Tapetum
$B-$Middle layer
$C-$Endothecium
  1. The function of labelled part $X$ is:
  1. Dehiscence.
  2. Mechanical.
  3. Nutrition.
  4. Protection.
  1. Select the incorrect statement.
  1. Microsporangium is generally surrounded by four wall layers$-$epidermis, endothecium, middle layers and tapetum.
  2. Outer three layers perform functions of protection and dehiscence of anthers.
  3. Cells of tapetum possess dense cytoplasm and generally have more than one nucleus.
  4. Cells of tapetum undergo meiosis and produce microspore tetrads.
  1. Which function oftapetum is correct?
  1. Helps in pollen wall formation.
  2. Transportation of nutrients to inner side of another.
  3. Synthesis of callase enzyme for separation of microspore tetrads.
  4. All of these.
→
For question, two statements are given$-$one labelled Assertion and the other labelled Reason. Select the correct answer to these questions from the codes $(a), (b), (c)$ and $(d)$ as given below.
Assertion : Tranquillizers are used to treat schizophrenia.
Reason: Tranquillizers are antipsychosis drugs.
→
For two statements are given$-$one labelled Assertion and the other labelled Reason. Select the correct answer to these questions from the codes $(a), (b), (c)$ and $(d)$ as given below.
Assertion: Allogamy includes both geitonogamy and xenogamy.
Reason: Allogamy needs abiotic or biotic external agencies for pollination.
→
For question two statements are given$-$one labelled Assertion and the other labelled Reason. Select the correct answer to these questions from the codes $(a), (b), (c)$ and $(d)$ as given below.
Assertion: The introduction of Nile perch in lake Victoria caused cichlids to become extinct.
Reason: Nile perch is an indigenous species of East Africa.
→
The purpose of biopiracy is :
→
For question, two statements are given$-$one labelled Assertion and the other labelled Reason. Select the correct answer to these questions from the codes $(a), (b), (c)$ and $(d)$ as given below.
Assertion: Regulator and operator genes are not associated with constitutive genes
Reason: Constitutive genes need not be repressed.
→
Two statements are given$-$one labelled Assertion and the other labelled Reason. Select the correct answer to these questions from the codes $(a), (b), (c)$ and $(d)$ as given below.
Assertion: Bacteriophage vectors are more advantageous than plasmid vectors.
Reason: Bacteriophage vectors can be easily detected at the time of cloning experiments.
→
For question two statements are given$-$one labelled Assertion and the other labelled Reason. Select the correct answer to these questions from the codes $(a), (b), (c)$ and $(d)$ as given below.
Assertion: Quantitative inheritance is called polygenic inheritance.
Reason: Several genes control the expression of a trait.
→