Agamete that is similar in shape, size, and behaviour to another gamete with which it can produce a zygote.
The fusing of gametes that are physically similar but physiologically separate is known as isogamy.
Isogametes are gametes that are formed in vegetative cells known as gametangia. Isogametes can be planogametes (e.g. Ulothrix, Chlamydomonas) or aplanogametes (e.g. Ulothrix, Chlamydomonas).