BiologicalClassification PYQs

Explanation:

Option 2 is correct. Plasmogamy means the fusion of cytoplasm (protoplasm) of two gametes, which may be motile or non-motile. Karyogamy (not option 1) is the fusion of the nuclei. Option 3 is incorrect because saprophytes feed on dead organic matter, whereas organisms that depend on living plants are parasites. Option 4 is incorrect because nitrogen fixation in cyanobacteria occurs in specialized cells called heterocysts, not sheath cells.

🧠 Did You Know?

In fungi, plasmogamy often occurs first, followed by karyogamy to form a diploid nucleus.

💡 NCERT Memory Line:

Plasmogamy = fusion of cytoplasm; Karyogamy = fusion of nuclei.

Explanation:

The incorrect statement is option 2. Cyanobacteria are photoautotrophs and carry out photosynthesis. Many cyanobacteria form specialized cells called heterocysts for nitrogen fixation, so they do have heterocysts in several species. They often form blooms in polluted or nutrient-rich water bodies, and they contain chlorophyll a, along with other pigments, which is similar to green plants.

🧠 Did You Know?

Cyanobacteria are sometimes called blue-green algae, but they are bacteria, not true algae. They play a key role in nitrogen cycling due to heterocysts in some species.

💡 NCERT Memory Line:

Cyanobacteria are photosynthetic and may fix nitrogen in heterocysts; they form blooms in polluted waters and possess chlorophyll a similar to green plants.

Explanation:

PPLO stands for Pleuropneumonia-Like Organism, which is the organism Mycoplasma pneumoniae. According to NCERT biology, PPLOs are very small, about 0.1 μm in size, much smaller than many bacteria. Thus the correct size is 0.1 μm (option 4).

🧠 Did You Know?

PPLOs lack a cell wall and have a flexible membrane, which helps them survive as small organisms in various environments.

💡 NCERT Memory Line:

PPLO organisms are extremely small, around 0.1 μm, illustrating how some pathogens can be much smaller than typical bacteria.

Explanation:

Inclusion bodies are reserve materials (like glycogen, lipids, pigments) that lie free in the cytoplasm and are not bounded by a membrane. They do not participate in the ingestion of food particles. Therefore, statement 2 is incorrect.

🧠 Did You Know?

NCERT describes inclusion bodies as reserve deposits in the cytoplasm, formed when resources are stored for later use.

💡 NCERT Memory Line:

Inclusion bodies: reserve materials in the cytoplasm, often not membrane-bound.

Explanation:

Viroids are tiny infectious agents consisting only of a short strand of RNA. They do not have a protein coat (capsid). Therefore they are naked RNA, free of any protein envelope. This matches option 2: “They have free RNA without protein coat.”

🧠 Did You Know?

Viroids are smaller than viruses and affect plants by interfering with their normal metabolism, without encoding proteins.

💡 NCERT Memory Line:

Viroids are naked RNA without a protein coat; they are infectious RNA particles lacking a capsid.

Explanation:

The incorrect statement is option 2. In NCERT, the infective part of a virus is its nucleic acid (DNA or RNA), not the protein coat. The protein coat (capsid) encases the nucleic acid but is not itself the genetic material. Hence, viruses are obligate parasites that need a host to reproduce. Viroids lack a protein coat, and prions are infectious proteins with no nucleic acid, consisting only of abnormally folded proteins.

🧠 Did You Know?

NCERT emphasizes that the key infectious nature of viruses lies in their nucleic acid, while prions are misfolded proteins and viroids are naked RNA without a capsid.

💡 NCERT Memory Line:

Viruses have nucleic acid enclosed in a protein coat; infective material is nucleic acid.

Explanation:
NCERT Page No. 16, 17 and 18

Spherical bacteria are cocci, rod-shaped are bacilli, comma-shaped are vibrio and spiral-shaped are spirilla.