1. Mosses and ferns share a common trait that makes water droplets a necessity for sexual reproduction. What is that trait?
2. Are the mosses well adapted to terrestrial life? Justify your answer.
3. Ferns display a dominant sporophyte generation (with large fronds). Describe the major advance in anatomy that enables most ferns to grow much larger than mosses.
5. Why did some botanists once believe that the whisk ferns should be classified together with the rhyniophytes?
6. Contrast microphylls with megaphylls in terms of structure, evolutionary origin, and occurrence among plants.
A violent thunderstorm moves through forested hills and valleys where summer rain has been scarce. A jagged fork of lightning strikes a tree, and it bursts into flame. Soon the flames reach dead and dry underbrush, and fire spreads to the surrounding trees. The fire rages rapidly through the forest, leaving a blackened and smoking landscape behind.
Though devastating, such fires are a natural part of the forest ecosystem. Life returns quickly following a fire in a natural grassland or forest, in part because some plants have adaptations that enable them to live with fire. One example, obvious from its common name, is fireweed. The seeds of fireweed not only survive fires, but are stimulated by high temperatures to break their dormancy and sprout. Another example is the lodgepole pine tree, which covers vast fire-prone areas in the Rocky Mountains and elsewhere. Its cones will not release their seeds unless the heat of a fire causes them to open.
Seeds are remarkable structures. They protect the plant embryo within them from environmental extremes through what may be a very long resting period. This and other properties have contributed to making seed plants the predominant plants on Earth. All of today's forests are dominated by seed plants.
In this chapter we will describe the defining characteristics of the seed plants as a group. We will survey the diversity of seed plants and describe the flowers and fruits that are characteristic of their most dominant group, the flowering plants. Finally, we will consider some of the unsolved problems in seed plant evolution.
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This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.