Mating is a biological process used by organisms for sexual reproduction. Mating occurs in all organisms, including animals, plants, fungi, and bacteria. Mating may require contact between opposite sex individuals, as with animals, but can also occur without any physical contact, as with pollination of vascular plants. Mating also encompasses the process occurring in bacteria and viruses in which homologous chromosomes of individuals are paired for genetic exchange resulting in the formation of a recombinant progeny.