Describe the various ways by which seeds are dispersed.
Seed dispersal takes place by various agent that is responsible for cross pollination; and this means to scatter seeds over a large area. The seeds of some of the plant disperse as seeds and some are dispersed in the form of fruits because they contain seeds inside them. There are various methods of seed dispersal that have been categorised into two main categories: Abiotic (like wind, gravity, water etc.) and Biotic (animal pollinators like insects).
Anemophily (wind pollination): It is the mode of transfer of pollen grains from anther to stigma through the agency of wind. The flowers that are wind pollinated are anemophilous. These flowers contains some adaptations like flowers are colourless, odourless and nectar-less; pollen grains are small, dry, dusty and sometimes saccate so that they can blow away easily to the long distances etc.
Hydrophily (water pollination): It is the mode of transfer of pollen grains from anther to stigma occurs through the agency water. The flowers that are water pollinated are hydrophilous flowers. These flowers contains some adaptations like flowers are small, colourless, odourless and nectar-less; pollen grains are unwettable, stigma are long and sticky etc. Dispersal by water takes place in some aquatic plants which is very rare and in some that grows near a water body. For example: Zostera, Hydrilla, Ceratophyllum etc.
Entomophily (insects pollination): It is the animal pollinator or biotic category in which the transfer of pollen grains from anther to stigma occurs through the agency of insects. The flowers that are insect pollinated are entomophilous flowers. These flowers contains some adaptations like flowers are usually large, brightly coloured and slowly to attract insect pollinators etc. The most common insect pollinators are as follows: moths, flies, butterflies, bees, beetles etc.
Dispersal by Humans: Human beings also help in dispersal of seeds during the farming.
There are much more methods for the dispersal of seeds like Ornithophily (pollination by birds), Chiropterophily (pollination by bats) etc.
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