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Sponges are able to reproduce asexually through budding. This is when a small piece of sponge is broken off but is still able to survive and grow into another sponge. Sponges are also able to repair damages to their bodies. These characteristics of sponges are ideal because even small parts of sponges may survive in the water.
"asexual reproduction is seen exclusively in lower plants!"
these were simple plants wid simple structure that could get their nutrition by easy means. In case of sponges direct gsaseous exchange through the outermost layer of cells in very simple metabolism to obtain nutrition.
however, in higher plants reproduction became sexual coz the environment fr growth i.e land ws not favourable enough wich resulted in development of complex systems for better survival ..... and one of them is sexual reproduction.
so it is just a matter of evolution ! and asexual reproduction occurs wen the organism has become fully matured n is going to degenerate because of getting fatigued of its continued functions. so instead of just degenerating the organism continues itself by renewing its processes via reproduction