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1. CELLS

2. Defination of cell Cell is a structural and functional uint of life. It is also called fundamental unit of life.

3. About cell Cells were first discovered by Robert Hooke in 1665. While examinig a thin slice of cork , Robert Hooke saw that the cork resembled the structure of a honeycomb consisting of many little compartments. Cork is asubstance which comes from the bark of a tree. Hooke observed these cork slices through a self-designed microscope.Robert hooke called these boxes cells. Cell is a Latin word for ‘a little room.’

4. Difference between Prokaryotic and eukaryotic Prokaryotic cell Eukaryotic cell Size of cell is small. Nucleus is absent. It contain single chromosome. Nucleolus is absent. Membarane bound cell organelles are absent. Cell division takes place by fission dr budding. Size of cell is large. Nucleus is present. It contain more than one chromosome. Nucleolus is present. Cell organelles such as plastids, lysosomes etc. are present. Cell division occures by mititic and meiotic.

5. Cell Theory In 1938, Jakob Matthias Schleiden(1804-1881), a German botanist, first proposed the idea that all plants consist of cells. A year later, in 1839, Theodor Schwann(1810-1882), a German zoologist, independently asserted that all animals and plants are made up of cells. This joint finding forms the basis of the cell theory. The cell theory was refined furtherin 1885, when another German biologist, R. Virchow presented the idea that all cells arise from pre-existing cells. Thus , cell theory comprises some postulates.

6. Postulates of cell theory All organisms are composed of cells and cell products. All metabolic reactions takes place in the cells. Thus, cells are structural and functional units of life. All cells arise from pre-existing cells only. Every organisms starts its life as a single cell.

8. Plant cell In plant cell, Cell wall, plasma membrane, nucleus, chromatin, endoplasmic reticulum, cytoplasm, chloroplast, ribosomes, mitochondria, dictyosome vacuole are present.

9. Animal cell In animal cell, plasma membarane, cytoplasm, nucleus, chromatin, ribosomes, mitochondrion, endoplasmic reticulum, golgi apparatus, golgi vesicle, present.

10. Present in both plant and animal cell Plasma membrane, ribosomes, cytoplasm, mitochondrion, endoplasmic reticulum, nucleus, chromatinare present. In plant cell golgi apparatus is known as dictyosome.

11. Differances between plant cell and animal cell Plant cell Animal cell Size of cell is large. Cell wall is absent. Plastids are present. Plant cell have a big vacuole. Plant cell have many simpler units of golgi apparatus, called dictyosome. Plant cells have centrosomeand centrioles. Size of cell is small.