<Image>
Moss sperm are motile and capable of swimming short distances to fertilize an egg. However, it was unknown until recently how sperm make their way from male to female gametophytes that may be separated by a distance of several centimeters or more.
What structure do moss sperm use for motility, and how does that reflect the evolution of land plants from green algae?

<Image>

Moss sperm are motile and capable of swimming short distances to fertilize an egg. However, it was unknown until recently how sperm make their way from male to female gametophytes that may be separated by a distance of several centimeters or more.

Besides springtails, are there other ways moss sperm may be transferred from male to female gametophytes?

Angiosperms such as grasses, oaks, and maples are wind pollinated. The ancestors of these subgroups were probably pollinated by insects, however. As an adaptive advantage, why might a species 'revert' to wind pollination? (Hint: Think about the costs and benefits of being pollinated by insects versus wind.) Why is it logical to observe that wind-pollinated species usually grow in dense stands containing many individuals of the same species? Why is it logical to observe that in wind-pollinated deciduous trees, flowers form very early in spring—before leaves form?

Moss sperm are motile and capable of swimming short distances to fertilize an egg. However, it was unknown until recently how sperm make their way from male to female gametophytes that may be separated by a distance of several centimeters or more. A friend in your biology study group claims that eggs in mosses are fertilized by spores. What is wrong with that statement?

<Image>

Moss sperm are motile and capable of swimming short distances to fertilize an egg. However, it was unknown until recently how sperm make their way from male to female gametophytes that may be separated by a distance of several centimeters or more.

Beyond the results presented here, what other evidence would be useful when drawing conclusions about the role of springtails in moss reproduction?

You have been hired as a field assistant for a researcher interested in the evolution of flower characteristics in orchids. Design an experiment to determine whether color, size, shape, scent, or amount of nectar is the most important factor in attracting pollinators to a particular species. Assume that you can change any flower's color with a dye and that you can remove petals or nectar stores, add particular scents, add nectar by injection, or switch parts among species by cutting and gluing.

<Image>

Moss sperm are motile and capable of swimming short distances to fertilize an egg. However, it was unknown until recently how sperm make their way from male to female gametophytes that may be separated by a distance of several centimeters or more.

Researchers hypothesized that small animals called springtails (a type of arthropod) facilitate sperm transfer in mosses. To test this hypothesis, the researchers grew patches of male and female mosses at varying distances from each other and in the presence or absence of springtails. They later checked to see how many sporophytes were found in each female patch (as an indicator that fertilization had occurred). Their results are shown in the graph here (** means P<0.01, * means P>0.05. What conclusions can be drawn about the role of the springtails during the reproductive cycle of the mosses?