What do you understand by the following terms a] osmosis b]diffusion c] active transport

Osmosis : a diffusion of a solvent (most of the time water molecules) through a membrane that is semipermeable in a area that is low solute concentration to an area of high solute concentration  

Diffusion : A net passive motion of particles (atoms, ions, or molecules) from a section which they are higher in concentration compared to areas in lower concentration.  It goes on until the concentration is all the same.

Active Transport : The motion  of ions or molecules along a cell membrane in the direction opposite of the diffusion or  from an area of lower concentration to one of higher concentration. Active transport needs the assistance of a certain protein known as a carrier protein which uses energy supplied by ATP.

genetic variation can be caused by mutation (which can create entirely new alleles in a population), random mating, random fertilization, and recombination between homologous chromosomes during meiosis (which reshuffles alleles within an organism's offspring).

that scientist would be robert hooke