Plant Cell Structure And Differences From Animal Cells

Step 1: Understanding Cell Wall in Different Organisms
Cell walls are structural components found in many organisms, providing support and protection. However, certain organisms lack a cell wall at all stages of their life cycle.
- Dinoflagellates: Most have a cell wall composed of cellulose plates, though some may lack it.
- Chrysophytes: They generally possess a siliceous (silica-based) cell wall.
- Slime Moulds: These have a cell wall during the spore-forming stage, though they may be absent in the vegetative phase.
- Protozoans: These are unicellular eukaryotic organisms that completely lack a cell wall in all life stages. They have a flexible plasma membrane instead.

Step 2: Identifying the Correct Answer
Since protozoans never possess a cell wall at any stage of their life cycle, the correct answer is Option (4) Protozoans.
Step 3: Verifying the Options - Option (1) Dinoflagellates (Incorrect – Many have cellulose cell walls)
- Option (2) Chrysophytes (Incorrect – Have silica-based cell walls)
- Option (3) Slime moulds (Incorrect – Have cell walls during spore formation)
- Option (4) Protozoans (Correct – No cell wall at any stage)
Thus, the correct answer is (4) Protozoans.

Step 1: Interpreting the reaction:
The given reaction represents the conversion of glutamic acid into glutamine. In this process, ammonia ( ) is incorporated, and energy is supplied through the hydrolysis of ATP into ADP and inorganic phosphate ( ).

Step 2: Determining enzyme X:
Reactions that involve the formation of a new bond between molecules using energy derived from ATP are catalyzed by enzymes known as synthetases.
In this specific case, the enzyme responsible for converting glutamate to glutamine is glutamine synthetase.

Step 3: Identifying enzyme class Y:
According to the IUBMB classification, enzymes are divided into six major classes:

• Oxidoreductases
• Transferases
• Hydrolases
• Lyases
• Isomerases
• Ligases

Since this reaction involves the joining of two molecules with the help of ATP, the enzyme belongs to the Ligases category, which corresponds to Class 6.

Step 4: Conclusion:
Thus, enzyme X is glutamine synthetase, and enzyme class Y is Class 6 (Ligases).

Step 1: Understanding Mobile Genetic Elements:
"Mobile genetic elements" are DNA sequences that can move around the genome. They are often called "jumping genes".
Step 2: Classification:
Transposons are broadly classified into two types:

• Class II (DNA Transposons): Move directly as DNA via a "cut and paste" mechanism.
• Class I (Retrotransposons): Move via an RNA intermediate. The DNA is transcribed into RNA, and then reverse-transcribed back into DNA (cDNA) which inserts elsewhere ("copy and paste").

Step 3: Conclusion:
The question specifically asks for elements replicating via an RNA intermediate. This describes Retrotransposons, which fall under the broad category of Transposons. Plasmids and Phages are vectors or separate DNA entities, not typically classified as mobile genetic elements of the host genome in this context.

1. In {Achyranthes} (family Amaranthaceae), flowers are borne on an elongated, unbranched axis without pedicels, forming a spike inflorescence. Hence, Assertion (A) is true.
2. In a spike, flowers are arranged directly on the main axis (rachis) and it belongs to the {racemose type} of inflorescence. In racemose inflorescences, the floral buds open in an acropetal order — the older flowers are at the base and the younger ones are towards the apex.
3. The Reason (R) states that the spike shows a basipetal arrangement of sessile flowers, which is incorrect because basipetal succession occurs in {cymose (determinate)} inflorescences, not in racemose ones like spikes.
4. Therefore, while the Assertion (A) is true, the Reason (R) is false. Hence, the correct answer is (3) (A) is true, but (R) is false.

Match each taxonomist to their classic work and the classification approach they are associated with:
I. Theophrastus is the ancient author of \emph{Historia plantarum} (W). Historically his scheme is proto-classificatory (here placed under D/W in the option).
II. Linnaeus authored \emph{Species plantarum} (X) and is famous for the Artificial (sexual) classification (C).
III. Bentham & Hooker wrote \emph{Genera plantarum} (Y) and their system is regarded as a Natural system (B).
IV. Hutchinson is known for emphasizing evolutionary/phylogenetic relationships and authored works that align with phylogenetic treatment of families (Z) — mapped to A.
Therefore the set corresponds correctly to the option (2).

1. Rockweeds (genus Fucus and similar brown algae) exhibit a diplontic life cycle: the multicellular phase is diploid (the thallus), and the only haploid stages are the gametes. Fertilisation produces a zygote that develops into the diploid thallus.
2. In diplontic life cycles, meiosis produces gametes directly (i.e., gametes are formed by meiosis), and there is no multicellular haploid generation.
3. Therefore the life cycle of rockweed (Fucus) is diplontic. Hence the correct answer is (2) Diplontic.

Salvinia: aquatic fern, floating, has balancing roots → I-C-Z
Hydrilla: submerged, gets water contact, heterosporous → II-D-W
Asparagus: succulent roots, Xylem cavity → III-B-X
Pistia: floating, no contact with soil, leaves form cladophyll → IV-A-Y
Hence, option (1) is correct.