Question

Select the correct combination of the statements(a-d) regarding the characteristics of certain organisms : (i) Methanogens are archaebacteria which produce methane in marshy area (ii) Nostoc is a filamentous blue green alga which fixes atmospheric nitrogen (iii) Chemosynthetic autotrophic bacteria synthesize cellulose from glucose (iv) Mycoplasma lack a cell wall and can survive without oxygen. The correct statements are :

• A. (ii) & (iii)
• B. (i),(ii) & (iii)
• C. (ii), (iii) & (iv)
• D. (i), (ii) & (iv)

Answer 1

The Correct Option is D

To solve the question, we must analyze each given statement and determine whether it is true or false based on biological knowledge:

1. Statement (i): Methanogens are archaebacteria which produce methane in marshy areas.
   Explanation: Methanogens are a group of Archaea that are known for their ability to convert carbon dioxide, hydrogen, and other compounds into methane. They thrive in oxygen-free (anaerobic) environments such as marshy areas.
   Thus, this statement is correct.
2. Statement (ii): Nostoc is a filamentous blue-green alga which fixes atmospheric nitrogen.
   Explanation: Nostoc is a cyanobacterium (commonly referred to as blue-green algae) that can fix atmospheric nitrogen. It forms filamentous colonies and has specialized cells called heterocysts that help it in nitrogen fixation.
   Thus, this statement is correct.
3. Statement (iii): Chemosynthetic autotrophic bacteria synthesize cellulose from glucose.
   Explanation: Chemosynthetic autotrophic bacteria obtain energy from the oxidation of inorganic substances rather than from light (as in photosynthesis). They are involved in the synthesis of organic compounds, but they do not synthesize cellulose from glucose. Instead, they typically produce carbohydrates through the fixation of carbon dioxide.
   Thus, this statement is incorrect.
4. Statement (iv): Mycoplasma lack a cell wall and can survive without oxygen.
   Explanation: Mycoplasmas are a type of bacteria that are characterized by the absence of a cell wall. This feature allows them to be flexible and take on various shapes. They are known to survive in oxygen-rich and oxygen-poor environments, thus they can survive without oxygen.
   Hence, this statement is correct.

After analyzing each statement, the correct combination of statements is (i), (ii), and (iv).