Diffusione delle piante

Plants can spread according to two modalities. The first is known as vegetative multiplication and consists of the production of new individuals from a part of an already present living organism. To the contrary, sexual reproduction requires the passage through a structure, known as seed, originated by the fusion of particular cells produced by one or two different plants. While the vegetative multiplication gives rise to individuals all identical among them and to the parent, the sexual reproduction induces the appearance of genetic variability, which is a key aspect to allow natural selection and consequently the evolution. The seed has also other functions: to facilitate the species spreading and to allow the plants to overcome periods with unfavorable climatic conditions (e.g. winter). Seeds are very different, in both size and shape and can remain viable for very long periods of time. Their diffusion can be facilitated by intervention of animals (namely birds, which feed with fleshy fruit) and the presence of particular structures, such as wings.