The basic building block of life is the cell. It first appeared on Earth some 4 billion years ago. Organisms can be categorised as unicellular (single cell) or multicellular depending on how many cells they contain. Microorganisms are the most common type of unicellular creature. Robert Hooke discovered cells in 1665. View this PPT to learn more about cells.

Apoorva

40 resources

1

60

0

Like