Reproduction and Fungi Structures

The science background section gives teachers more detailed information on the phenomena students explore in this unit. Here is an excerpt of the science background section from this lesson on the phenomena of reproduction and fungi structures. 

For many years, scientists had a hypothesis about the evolutionary advantage of sexual reproduction. They thought that the genetic variation of sexual reproduction made species more able to adapt to changes in their environment. This would make them more likely to survive as a species. According to this hypothesis, if some individuals had traits that could help them survive in a changed environment, those individuals would be able to survive and reproduce even if other individuals couldn’t survive.

Scientists didn’t have evidence to support that hypothesis. In recent years, scientists have been conducting experiments to help them answer the question of why sexual reproduction is so useful.

Sexual and Asexual

One way to do this is to compare a species of organisms that can reproduce both sexually and asexually. For example, a group of scientists has studied a group of small fish called topminnows in Mexico. Some populations of topminnow reproduce asexually. Other populations of topminnow reproduce sexually.

The scientists knew that a parasitic worm was common in the topminnow population. The worm invaded some of the fish and harmed them, making it harder for them to reproduce. The scientists found that the population of topminnows that reproduced asexually had many more parasitic worms than the population of topminnows reproducing sexually.

These findings support the hypothesis that sexual reproduction gives organisms an evolutionary advantage. The genetic variation gives the sexually reproducing population a better chance of adapting to and surviving the parasitic worm. Studies of other species support these findings as well, but scientists are continuing to research their question.

Structures of Fungi

When the mushroom is ready to reproduce, it releases its spores into the environment. Those spores that land in a good environment, such as soil or plant litter, will begin to develop into a new organism.

First, the spores begin to grow hyphae (threadlike structures that can fuse together into a network of tissues called mycelium). Once the network of mycelium grows large enough, it forms mushrooms. A mature mushroom can produce millions or billions of spores in a single day.

Most fungi reproduce asexually most of the time. This is because of the advantages to asexual reproduction: it is more efficient, taking less time and producing more offspring. In asexual reproduction, the spores hold a copy of the parent’s full set of genetic information.

However, sometimes fungi need to be able to adapt to a changed environment, and so they can also reproduce sexually. This usually happens when nutrients or water are scarce.