Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Vascular Seedless Plants Jessica Harwood Douglas Wilkin, Ph.D. Say Thanks to the Authors Click http://www.ck12.org/saythanks (No sign in required) To access a customizable version of this book, as well as other interactive content, visit www.ck12.org AUTHORS Jessica Harwood Douglas Wilkin, Ph.D. EDITOR Douglas Wilkin, Ph.D. CK-12 Foundation is a non-profit organization with a mission to reduce the cost of textbook materials for the K-12 market both in the U.S. and worldwide. Using an open-source, collaborative, and web-based compilation model, CK-12 pioneers and promotes the creation and distribution of high-quality, adaptive online textbooks that can be mixed, modified and printed (i.e., the FlexBook® textbooks). Copyright © 2015 CK-12 Foundation, www.ck12.org The names “CK-12” and “CK12” and associated logos and the terms “FlexBook®” and “FlexBook Platform®” (collectively “CK-12 Marks”) are trademarks and service marks of CK-12 Foundation and are protected by federal, state, and international laws. Any form of reproduction of this book in any format or medium, in whole or in sections must include the referral attribution link http://www.ck12.org/saythanks (placed in a visible location) in addition to the following terms. Except as otherwise noted, all CK-12 Content (including CK-12 Curriculum Material) is made available to Users in accordance with the Creative Commons Attribution-Non-Commercial 3.0 Unported (CC BY-NC 3.0) License (http://creativecommons.org/ licenses/by-nc/3.0/), as amended and updated by Creative Commons from time to time (the “CC License”), which is incorporated herein by this reference. Complete terms can be found at http://www.ck12.org/about/ terms-of-use. Printed: July 15, 2015 CONTRIBUTORS Doris Kraus, Ph.D. Niamh Gray-Wilson Jean Brainard, Ph.D. Sarah Johnson Jane Willan Corliss Karasov www.ck12.org C HAPTER Chapter 1. Vascular Seedless Plants 1 Vascular Seedless Plants • Give properties of vascular seedless plants. • Describe examples of vascular seedless plants. How do these trees and mosses differ? The trees tower in the sky, while the mosses carpet the forest floor. Mosses, like the first plants, are restricted to life near the ground because they lack vascular system. Only with a vascular system can these trees transport sugars, nutrients, and water up and down their tall trunks. The evolution of the vascular system was a big step in the evolutionary history of plants. Vascular Seedless Plants For these plants, the name says it all. Vascular seedless plants have vascular tissue but do not have seeds. Remember that vascular tissue is specialized tissue that transports water and nutrients throughout the plant. The development of vascular tissue allowed these plants to grow much taller than nonvascular plants, forming ancient swamp forests. Most of these large vascular seedless plants are now extinct, but their smaller relatives still remain. Vascular tissue includes xylem, which transports water from the roots to the rest of the plant; and phloem, which transports sugars and nutrients from the leaves throughout the plant. Seedless vascular plants include: 1. 2. 3. 4. Clubmosses. Ferns. Horsetails. Whisk ferns. 1 www.ck12.org Clubmosses Clubmosses are so named because they can look similar to mosses (Figure below). Clubmosses are not true mosses, though, because they have vascular tissue. The “club” part of the name comes from club-like clusters of sporangia found on the plants. One type of clubmoss is called the "resurrection plant" because it shrivels and turns brown when it dries out but then quickly turns green when watered again. FIGURE 1.1 Clubmosses can resemble mosses; however, clubmosses have vascular tissue, while mosses do not. Ferns Ferns are the most common seedless vascular plants (Figure below). They usually have large divided leaves called fronds. In most ferns, fronds develop from a curled-up formation called a fiddlehead (Figure below). The fiddlehead looks like the curled decoration on the end of a stringed instrument, such as a fiddle. Leaves unroll as the fiddleheads grow and expand. Ferns grow in a variety of habitats, ranging in size from tiny aquatic species to giant tropical plants. Horsetails Horsetails have hollow, ribbed stems and are often found in marshes (Figure below). Whorls of tiny leaves around the stem make the plant look like a horse’s tail, but these soon fall off and leave a hollow stem that can perform photosynthesis. This is unusual since photosynthesis most often occurs in leaves. The stems are rigid and rough to the touch because they are coated with a scratchy mineral. Because of their scratchy texture, these plants were once used as scouring pads for cleaning dishes. Whisk Ferns Whisk ferns have green branching stems with no leaves, so they resemble a whisk broom (Figure below). Another striking feature of the whisk ferns is its spherical yellow sporangia. 2 www.ck12.org Chapter 1. Vascular Seedless Plants FIGURE 1.2 Ferns are common in the understory of the tropical rainforest. FIGURE 1.3 The first leaves of most ferns appear curled up into fiddleheads. Vocabulary • club moss: Vascular seedless plant that looks similar to the nonvascular moss, but with true roots, stems, and leaves. • fern: Vascular seedless plant with large divided leaves called fronds. • horsetail: Vascular seedless plant with hollow, ribbed stems; it is often found in marshes. • vascular seedless plant: Plant with vascular tissue but no seeds or flowers. • whisk fern: Vascular seedless plant with green branching stems, yellow spherical sporangia, and no leaves. Summary • Vascular seedless plants have vascular tissue, a specialized tissue that transports water and nutrients throughout the plant. • Vascular seedless plants include the club mosses, ferns, whisk ferns, and horsetails. 3 www.ck12.org FIGURE 1.4 Horsetails are common in marshes. Explore More Use the resource below to answer the questions that follow. • Seedless Vascular Plants at http://www.youtube.com/watch?v=VKS-smv1g7A (1:32) MEDIA Click image to the left or use the URL below. URL: http://www.ck12.org/flx/render/embeddedobject/57439 1. How many species of ferns and horsetails have scientists identified today? 2. How do scientists feel the present day diversity of ferns and horsetails compares to the diversity of these plants before the appearance of plants with seeds? 3. What sex are the spores of a fern? 4. What happens to the fertilized embryo of a fern? Review 1. 2. 3. 4. 5. 4 Why are the vascular seedless plants different from the nonvascular plants? What are two examples of vascular seedless plants? What is the role of vascular tissue in plants? What was the primary result of the evolution of vascular tissue in plants? What is the most common seedless vascular plant? www.ck12.org Chapter 1. Vascular Seedless Plants FIGURE 1.5 Whisk ferns have yellow sporangia and no leaves. References 1. Benny Mazur. Clubmosses can resemble mosses; however, clubmosses have vascular tissue, while mosses do not. CC BY 2.0 2. Photography by Kat. Ferns are common in the understory of the tropical rainforest. CC BY 2.0 3. David Sim. The first leaves of most ferns appear curled up into fiddleheads. CC BY 2.0 4. Bradley Davis/BackpackPhotography. Horsetails are common in marshes.. CC BY 2.0 5. Forest and Kim Starr/Starr Environmental. Whisk ferns have yellow sporangia and no leaves. CC BY 3.0 5