Q.Robert Hooke first observed and named 'cells' in 1665 while examining a thin slice of:
Concept understanding — Cell Theory
Before microscopes were good enough to reveal life's inner detail, no one knew that a leaf, a fish and a human being were all built from the same basic material. The cell theory is the great generalisation that finally answered two questions at once: what is every living body made of, and where does every cell come from?
The theory was not the discovery of one person but was assembled and refined over the mid-nineteenth century:
- Matthias Schleiden, a botanist, studied many plants and concluded that all plants are made of different kinds of cells that build up the plant's tissues.
- Theodore Schwann, a zoologist, examined many animal cells, noticed that cells are bounded by a thin outer layer (the plasma membrane), and proposed that the bodies of both animals and plants are made of cells and the products of cells.
- Working together, Schleiden and Schwann formulated the cell theory — but their version had a gap: it did not explain how new cells actually arise.
- Rudolf Virchow closed that gap, showing that cells divide and that every new cell comes from a pre-existing cell — the idea captured in the phrase Omnis cellula-e cellula. This gave the theory its final form.
As understood today, the cell theory rests on two statements:
- All living organisms are composed of cells and the products of cells.
- All cells arise from pre-existing cells.
The second point is the one Virchow added, and it carries a powerful meaning: cells never appear from nothing. Every cell alive today descends in an unbroken line from an earlier cell, which is why life is described as continuous.
The cell theory matters because it unifies all of biology under a single framework — it tells us that the cell is the universal unit of life and that living things share a common building block and a common origin.
"Cell theory postulates class 11 biology" and "Schleiden Schwann Virchow contribution NCERT" are common searches this history-and-statement explanation matches directly, since cell theory is introduced at the start of the Cell: The Unit of Life chapter in the NCERT/CBSE Class 11 Biology syllabus. The Virchow addition of "omnis cellula-e cellula," highlighted above, is a frequently asked NEET fact.
[!TLDR]
Hooke examined a thin slice of cork in 1665 and named the honeycomb-like compartments he saw "cells."
[!ANSWER]
(b) Cork
In 1665, Robert Hooke examined a thin slice of cork under a compound microscope of his own design. He observed a honeycomb-like pattern of small, empty, box-shaped compartments, which reminded him of the small rooms (cells) in a monastery, and so he named them "cells." What he actually saw were the dead cell walls of cork tissue, since cork consists of non-living cells; he had no means of observing the living cell contents that Leeuwenhoek would later be the first to see.
[!ANSWER]
(b) Cork
Recall the specific plant material (cork) that Hooke examined when he first coined the term "cell."
Confusing Hooke's cork observation with Leeuwenhoek's later observation of living cells in pond water.
- CBSE 2026Set ANNUAL1 markMCQQ.Cell is called the structural and functional unit of life because:(a) All cells have nuclei.(b) All functions of organisms arise from cellular activity.(c) Cells are visible to naked eye.(d) Cells divide only once.
›Reveal solutionSolution
A cell is called the structural and functional unit of life because it is both the smallest self-contained structural building block of a body AND the smallest unit capable of carrying out life's processes (metabolism, growth, response, reproduction) on its own.
Structurally, every tissue, organ, and organism is built up from cells — there is no level of organisation smaller than a cell that is itself alive. Functionally, every life process you can name — respiration, protein synthesis, excitability, division — happens inside cells, using cell organelles. A unicellular organism like Amoeba performs all of life's functions within one single cell, which is direct proof that a cell alone is sufficient to sustain life; in multicellular organisms, these same functions are simply distributed among specialised cells working together, but the functions still originate at the cellular level.
The other options are incorrect because: not all cells have nuclei (mature RBCs and prokaryotic cells lack a true nucleus, yet they are still functional cells); visibility to the naked eye is not a defining property (most cells are microscopic); and cells certainly do not divide "only once" — cell division is a repeated, regulated process (the cell cycle).
✓Final answer(b) All functions of organisms arise from cellular activity.
- CBSE 2026Set ANNUAL1 markMCQQ.According to cell theory, new cells originate from :(a) Fermentation(b) Pre-Existing cells(c) Regeneration of old cells(d) Abiotic synthesis
›Reveal solutionSolution
According to cell theory, every new cell is formed by the division of an already-existing cell.
The cell theory was proposed by Schleiden and Schwann (1838-39), who stated that all plants and animals are composed of cells and that the cell is the basic unit of life. This was later expanded by Rudolf Virchow (1855), who added the crucial idea, summarised in the Latin phrase 'Omnis cellula-e cellula' ('every cell arises from a pre-existing cell'). This means new cells are never formed by spontaneous/abiotic synthesis or fermentation, and are not simply 'regenerated' from non-cellular material — they always arise through the division of cells that already exist.
✓Final answerThe correct option is (b) Pre-Existing cells — new cells originate only from the division of already-existing cells.
- CBSE 2022Set TERM11 markMCQQ.Cell theory was given by(a) A. V. Leeuwenhoek(b) Robert Hooke(c) Schwann & Schleiden(d) Brown & Virchow
›Reveal solutionSolution
The cell theory in its original form was proposed jointly by Schleiden and Schwann.
History of cell theory: Robert Hooke first observed and named 'cells' in cork tissue in 1665 (but these were dead cell walls, not living cells) using a self-designed microscope. Antony van Leeuwenhoek was the first to observe and describe a living cell (in 1674). Building on decades of microscopic observation, Matthias Schleiden (a botanist, 1838) and Theodor Schwann (a zoologist, 1839) together formulated the cell theory, stating that all plants and animals are composed of cells and that the cell is the basic unit of life. Rudolf Virchow later (1855) extended this with the crucial addition that all cells arise from pre-existing cells ('Omnis cellula-e cellula'), which corrected the earlier idea that cells arose de novo from non-cellular material.
✓Final answer(c) Schwann & Schleiden.
- CBSE 2022Set ANNUAL1 markMCQQ.___________ is an exception to Cell Theory.(a) Fungi(b) Bacteria(c) Mycoplasma(d) Virus
›Reveal solutionSolution
Viruses lack cellular organisation and cannot multiply independently, which is why they are considered an exception to the Cell Theory.
The Cell Theory (Schleiden, Schwann, and later extended by Virchow) states that:
- All living organisms are composed of cells.
- The cell is the basic structural and functional unit of life.
- All cells arise from pre-existing cells.
Fungi and Bacteria are both truly cellular — bacteria are prokaryotic cells and fungi are eukaryotic cells, so they follow the Cell Theory. Mycoplasma, though the smallest known cellular organism, still possesses a cell membrane and cytoplasm and is cellular. Viruses, in contrast, are non-cellular — they consist only of a nucleic acid core (DNA or RNA) surrounded by a protein coat (capsid), have no cytoplasm, no cell membrane of their own, and cannot carry out metabolism or reproduce unless they infect and take over the machinery of a living host cell. Because of this acellular, obligate-parasitic nature, viruses are treated as an exception to the Cell Theory.
✓Final answerThe correct option is (d) Virus — viruses are acellular and are the true exception to the Cell Theory.
- CBSE 2018Set zoology1 markMCQQ.New cells generate from:(a) Bacterial fermentation(b) Regeneration of old cells(c) Pre-existing cells(d) Abiotic material
›Reveal solutionSolution
New cells generate only from pre-existing cells, by cell division — this is a core part of the Cell Theory and rules out spontaneous generation.
One of the fundamental postulates of the Cell Theory (extended by Rudolf Virchow in 1855) is "Omnis cellula-e cellula" — every cell arises from a pre-existing cell, through the process of cell division (mitosis or meiosis). This directly disproved the earlier idea of spontaneous generation of cells from non-living matter.
Checking the options: (A) bacterial fermentation is a metabolic process, not a mode of cell origin; (B) "regeneration of old cells" is not how new cells arise — regeneration refers to replacement/repair of lost body parts using new cells produced by division, not old cells being converted; (D) abiotic (non-living) material cannot give rise to a cell — this idea (spontaneous generation) was scientifically disproved. Only pre-existing cells, by division, give rise to new cells.
✓Final answerThe correct option is (c) Pre-existing cells.
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