CLASS 9 BIOLOGY – CELL: ENGLISH NOTES
1. Discovery of the Cell
Robert Hooke observed a thin slice of cork in 1665 using a microscope. He saw small, empty, honeycomb-like
compartments and called them “cells.” His observations were published in Micrographia.
2. Discovery of the Living Cell
Antonie van Leeuwenhoek observed living microscopic organisms in pond water in 1674. This showed that cells were not
simply empty compartments but could be living structures.
3. Cell Theory
Matthias Schleiden and Theodor Schwann proposed the cell theory in 1838–39. Its main ideas are: all living organisms
are made of cells; the cell is the basic structural and functional unit of life; and cells arise from pre-existing cells.
4. Modern Cell Theory
Rudolf Virchow added the important idea that new cells arise from pre-existing cells. The statement is commonly
expressed as “Omnis cellula e cellula.”
5. Plant Cell and Animal Cell
Plant cells have a cell wall, chloroplasts and usually a large central vacuole. Animal cells do not have a cell wall or
chloroplasts and generally have smaller vacuoles. Both contain a cell membrane, cytoplasm, nucleus and other major
organelles.
1. Discovery of the Cell
Robert Hooke observed a thin slice of cork in 1665 using a microscope. He saw small, empty, honeycomb-like
compartments and called them “cells.” His observations were published in Micrographia.
2. Discovery of the Living Cell
Antonie van Leeuwenhoek observed living microscopic organisms in pond water in 1674. This showed that cells were not
simply empty compartments but could be living structures.
3. Cell Theory
Matthias Schleiden and Theodor Schwann proposed the cell theory in 1838–39. Its main ideas are: all living organisms
are made of cells; the cell is the basic structural and functional unit of life; and cells arise from pre-existing cells.
4. Modern Cell Theory
Rudolf Virchow added the important idea that new cells arise from pre-existing cells. The statement is commonly
expressed as “Omnis cellula e cellula.”
5. Plant Cell and Animal Cell
Plant cells have a cell wall, chloroplasts and usually a large central vacuole. Animal cells do not have a cell wall or
chloroplasts and generally have smaller vacuoles. Both contain a cell membrane, cytoplasm, nucleus and other major
organelles.
