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Cells have always been inside plants and animals. But they are so tiny that nobody saw them for thousands of years. Things changed when microscopes were made in the seventeenth century.
How Cells Were Discovered
- Most cells are too tiny to see.
- The 1600s brought the first microscopes.
- These magnified things many times over.
- Now cell details could be studied.
Example 1 — Robert Hooke and Cork
- In 1665, Robert Hooke looked at a thin slice of cork under a microscope.
- He saw tiny empty boxes, like small rooms.
- He called each small room a cell — the first time the word was used.
Example 2 — Antonie van Leeuwenhoek
- He made stronger microscopes with more than 200 times magnification.
- He saw tiny animals in water, blood cells, yeast and even bacteria.
- So he is called the Father of Microbiology.
Important Points
- "Cell" comes from the Latin word for a small room.
- Hooke's cork cells were dead, so he saw only empty walls.
- Today's microscopes can show objects one-millionth of a metre wide.
Definition — Cell
The tiny box-like unit that makes up the body of every living thing.
The Cell Theory
- Schleiden (1838): all plants are cells.
- Schwann (1839): all animals are cells.
- Together this became the cell theory.
- New cells come from older cells.
Example 1 — A Mango Plant
- A mango plant is a living thing.
- Its roots, stem and leaves are all made of cells.
- This fits the cell theory — every plant is made of cells.
Example 2 — A Dog
- A dog is an animal.
- Its skin, muscles and bones are all made of cells.
- This fits the cell theory — every animal is made of cells.
Important Points
- Schleiden studied plants; Schwann studied animals — remember the pairing.
- Later, Virchow added the idea that cells only arise from cells.
- The cell theory applies to every living organism without exception.
Definition — Cell Theory
The cell is the basic unit of structure and function of all living things, and all cells come from earlier cells.
Objective Type Questions Q1(a) - Page 34 Lakhmir Singh
Question
Name the instrument essential for the study of cells.
Show answer
Microscope.
Explanation
- Cells are too small to see with the naked eye.
- A microscope magnifies them many times.
- So a microscope is needed to study cells.
Objective Type Questions Q1(b) - Page 34 Lakhmir Singh
Question
Name the scientist who observed a thin slice of cork through a microscope and coined the term cell.
Show answer
Robert Hooke.
Explanation
- In 1665, Robert Hooke looked at a thin slice of cork.
- He saw tiny empty boxes, like small rooms.
- He named each box a cell.
Objective Type Questions Q2(b) - Page 34 Lakhmir Singh
Question
Fill in the blank: The cytoplasm and nucleus make up the ______.
Show answer
Protoplasm.
Explanation
- Protoplasm is all the living matter in a cell.
- It includes the cytoplasm and the nucleus.
- So cytoplasm and nucleus together make protoplasm.
Multiple Choice Questions Q3 - Page 36 Lakhmir Singh
Question
The cell was discovered by: (a) Robert Boyle (b) Charles Darwin (c) Robert Koch (d) Robert Hooke
Show answer
(d) Robert Hooke.
Explanation
- Robert Hooke discovered and named the cell in 1665.
- He saw it in a thin slice of cork.
Multiple Choice Questions Q4 - Page 36 Lakhmir Singh
Question
The living matter in a cell is called: (a) endoplasm (b) protoplasm (c) cytoplasm (d) cell sap
Show answer
(b) protoplasm.
Explanation
- All the living matter in a cell is the protoplasm.
- It is made of the cytoplasm and the nucleus.
