Ch. 28 - Green Algae and Land Plants

Problem 12

Chapter 27, Problem 12

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?

Verified step by step guidance

Moss sperm use flagella for motility. Flagella are long, whip-like structures that protrude from the sperm cells and enable them to swim through water to reach the egg.

The presence of flagella in moss sperm is a reflection of their evolutionary heritage from green algae, which also use flagella for motility in water environments.

This evolutionary trait suggests that early land plants, like mosses, still depended on water for reproduction, similar to their aquatic ancestors, the green algae.

The reliance on water for fertilization in mosses indicates that the transition from aquatic to terrestrial life involved gradual adaptations to reduce dependency on water for reproduction.

Over time, more advanced land plants developed other reproductive strategies, such as pollen and seeds, which allowed them to reproduce without the direct need for water, further adapting to terrestrial environments.

Verified Solution

Video duration:

33s

This video solution was recommended by our tutors as helpful for the problem above.

Was this helpful?

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Moss Sperm Motility

Moss sperm are motile cells that swim through water to reach and fertilize the egg. They possess flagella, which are whip-like structures that enable movement. This motility is crucial for reproduction in mosses, as they rely on water for sperm to travel from male to female gametophytes, reflecting their adaptation to a terrestrial environment.

Gametophyte Generation

In mosses, the gametophyte generation is the dominant life stage, producing gametes (sperm and eggs) for sexual reproduction. This generation is haploid, meaning it contains a single set of chromosomes. Understanding the role of gametophytes is essential for grasping how mosses reproduce and how their reproductive strategies differ from those of vascular plants.

Evolution of Land Plants

The evolution of land plants from green algae involved significant adaptations, including the development of structures for reproduction and water retention. Mosses represent an early branch of land plants, showcasing traits like motile sperm and reliance on water for fertilization. This evolutionary transition highlights the importance of gametophyte structures and reproductive strategies in adapting to terrestrial environments.

Recommended video:

Guided course

12:33

Land Plants

Related Practice

Textbook Question

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?

554

views

Textbook Question

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.

336

views

Textbook Question

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?

334

views

Textbook Question

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?

371

views

Textbook Question

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?