In which organism does reproduction occur through binary fission?

Which of the following is an artificial method of vegetative propagation?

What happens when a mature $Spirogyra$ filament attains considerable length?

Some plants do not produce seeds. For such plants,parts like roots,stem,and leaves are used to develop into new plants.
$(a)$ Identify the process.
$(b)$ Which type of reproduction is it—sexual or asexual? Answer with reason.
$(c)$ Give any two examples of this process.

Vegetative propagation refers to the formation of new plants from:

An organism which is a worm,has very simple 'eyes',that are really eye spots which detect light. Name that organism.