Final answer:
A genetically distinct individual tree or plant that arises from a zygote through sexual reproduction is known as a sporophyte, which is part of the plant's lifecycle that includes the alternating gametophyte stage.
Step-by-step explanation:
An individual tree or plant produced by sexual reproduction, which arises from a zygote, is a genetic individual known as a sporophyte. During sexual reproduction, plants undergo a lifecycle that includes two distinct stages: the gametophyte stage and the sporophyte stage.
The gametophyte is haploid and produces male and female gametes through mitosis. When these gametes fuse, they form a diploid zygote. This zygote will then undergo multiple rounds of cell division, or mitosis, to develop into a multicellular plant called a sporophyte. In plants like Bryophyllum or bulb-bearing ferns, new plants can also develop through a process known as somatic embryogenesis, wherein cells other than the zygote can give rise to new multicellular organisms.