Spores are kind of like seeds in that they can be carried on the wind or rain, spreading the fungus to new places. Some species can do both sexual and asexual reproduction, depending on environmental conditions. Microbes in the protist category reproduce in a number of ways. Algae, for example, can reproduce without sex. The nucleus of the algal cell divides by mitosis and moves to opposite ends of the cell.
Some species can reproduce sexually.
Some do both. Viruses cannot reproduce on their own, which is one reason people debate whether they should be counted as living creatures. But when they're inside a suitable host cell, all they do is reproduce and they do it well. They take over the host cell's machinery and use it to make copies of their genes and proteins. These genes and proteins come together to make new viruses, which eventually escape the host cell and drift off to infect new cells.