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Which of the following is NOT an example of a single cell that constitutes a complete organism?
Amoeba
Chlamydomonas
Paramoecium
Cycas
Cycas
Cycas is a genus of gymnospermous plants which are multicellular, seed-bearing vascular plants. In contrast, Amoeba, Chlamydomonas, and Paramoecium are single-celled (unicellular) organisms that perform all life processes within a single cell.
Cycas is a genus of gymnospermous plants which are multicellular, seed-bearing vascular plants. In contrast, Amoeba, Chlamydomonas, and Paramoecium are single-celled (unicellular) organisms that perform all life processes within a single cell.
A single-celled organism is like a studio apartment where one room serves as the kitchen, bedroom, and office all at once. Cycas is like a skyscraper with thousands of specialized rooms, each designated for a specific function.
CAP = Unicellular (Chlamydomonas, Amoeba, Paramoecium); Cycas = Gymnosperm (Multicellular)
Unicellular organisms are composed of a single cell that carries out essential life functions such as nutrition, respiration, excretion, and reproduction independently. Multicellular organisms like Cycas possess complex tissue systems (xylem, phloem, epidermal tissues) consisting of millions of specialized cells organized into organs like roots, stems, and leaves.
Unicellular organisms execute all life functions (digestion, respiration, excretion, reproduction) within a single cell boundary.
Cycas belongs to Gymnosperms (non-flowering, naked-seeded plants) and exhibits high structural organization.
Amoeba is a unicellular protozoan moving via pseudopodia.
Chlamydomonas is a unicellular green alga with flagella.
Paramoecium is a slipper-shaped unicellular protozoan covered with cilia.
Used as fundamental biological models to study basic cellular processes, membrane transport, and cilia/flagella movement.
| Feature | Unicellular (Amoeba/Chlamydomonas/Paramoecium) | Multicellular (Cycas) |
|---|---|---|
Cell Number | Single cell | Millions of specialized cells |
Tissue Differentiation | Absent | Present (Xylem, Phloem, Epidermis) |
Kingdom | Protista / Plantae (micro-algae) | Plantae (Gymnospermae) |
Standard Classification: Amoeba and Paramoecium belong to Kingdom Protista (Protozoa). Chlamydomonas is classified under Kingdom Protista or Plantae (Green Algae). Cycas belongs to Kingdom Plantae (Division Gymnospermae).
Option A (Amoeba) is wrong because it is a unicellular protozoan.
Option B (Chlamydomonas) is wrong because it is a single-celled microscopic alga.
Option C (Paramoecium) is wrong because it is a unicellular ciliated organism.
Option D is correct — Cycas is a multicellular gymnosperm plant and not a single-celled organism.
For RRB ALP exam questions, remember that algae like Chlamydomonas and Chlorella are single-celled, while gymnosperms (Cycas, Pinus) and angiosperms are always complex multicellular plants.