Final answer:
In mosses and ferns, flagellated sperm rely on moisture to swim from the male antheridium to the female archegonium in order to fertilize an egg. Moist environments are crucial for this process, distinguishing their reproduction from many land animals where direct gamete contact occurs.
Step-by-step explanation:
In mosses and ferns, sperm reaches the egg through the aid of water. These plants belong to groups like the bryophytes and seedless tracheophytes, which include club mosses, horsetails, ferns, and whisk ferns. The reproductive process begins when the male reproductive organ, the antheridium, produces sperm that must then swim through a film of water to reach the female reproductive organ, the archegonium, where the egg is located. Moisture is critical for this part of the fern lifecycle, as sperm are flagellated and require a watery medium to reach and fertilize the egg. Once fertilization occurs, the zygote develops into a new sporophyte and the cycle repeats itself. This reproductive strategy is distinct from that of many land animals, which involves direct contact between male and female gametes without the intermediary of water.