Why reproduce? Asexual reproduction

Four common kinds of asexual reproduction. In binary fission the nucleus divides by mitosis and then the cell splits into two cells, each a new individual. Amoeba, Paramecium, simple algae and bacteria reproduce like this in suitable conditions. When conditions are bad, an Amoeba makes a protective coat around itself and divides several times inside it, and the young leave when the conditions improve. In budding a new individual grows out from the parent. In yeast a small bud forms on the side of the cell while the nucleus divides by mitosis in two: one nucleus stays and the other moves into the bud. The bud may separate or stay joined to form a colony. In sponges and Hydra the bud is a cellular outgrowth from the body wall that forms when interstitial cells divide and change; it grows into a small copy of the parent and usually separates. These animals also reproduce sexually. In regeneration an organism rebuilds lost parts. It is common in plants and in some animals such as sponges, Hydra, some worms and the starfish. A planaria, a flat freshwater worm, can be cut across or lengthways and each piece can grow into a whole worm, and a starfish arm with part of the central disc can grow into a whole star over a period that may reach a year. In higher animals the ability is lower: in some crustaceans and amphibians it restores only the cut part, and in higher vertebrates it is no more than healing of wounds. In sporulation the organism makes spores. A spore holds a nucleus and a little water in a thick coat. It leaves the parent and spreads through the air. In a suitable place it absorbs water, its coat splits and it divides by mitosis into a new individual. Bread mould, mushrooms, some algae and ferns do this. Spores let a species spread quickly, survive hard conditions and reach distant places.