Number of Cells
Human beings consist of trillions of cells. Unicellular organisms consist of single cells whereas multicellular organisms consist of more than one cell. Every living organism starts its life from a single cell, that is a fertilized egg and then it further divides into thousands and then millions. Unicellular organisms are capable of performing all required functions similar to multicellular organisms. Unicellular organisms like amoeba capture the food digest it and then excretes it out. These organisms also grow and reproduce. In multi-cellular organisms, these similar functions are performed by a group of special cells known as tissues and later on these tissues form the organs.
Cell Number, Shape and Size – Class 8 Notes
Organisms show Variety in Cell Number, Shape, and Size: Human beings consist of trillions of cells. Single-celled organisms are known as unicellular organisms—for example- bacteria, protists, and yeast. Multi-cellular organisms consist of more than one cell. Examples are humans, cows, dogs, and so on. Cells provide shape to the body which can be rounded, spherical, or elongated. In some organisms, the size can be as small as 0.0001mm, and large in some organisms up to six to twelve inches.
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