Reading Essentials for Biology Glencoe (794133), страница 55
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Threadlike green algae floating in a pond absorb water andnutrients directly into cells. How will land-based plants get waterand nutrients? For most land plants, the only available water andnutrients are in the soil. Only the part of the plant that is in thesoil can absorb the nutrients. Land plants had to adapt to absorbwater and nutrients.You already have learned about one adaptation. The waxy cuticle creates a barrier that helps prevent water in the plant’s tissuesfrom evaporating. You can feel the smooth, somewhat slippery,waxy cuticle if you run your fingers over the leaves or stems ofsome houseplants.Reproduction on land was another challenge. Algae releasegametes, or male and female sex cells, into the water where fertilization takes place.
Once on land, plants had to adapt to protectthe gametes from drying out. Another problem was exposure towind and weather. Land plants also had to develop structures tohelp them grow against the force of gravity. Over the past 440million years, plants have developed many adaptations.What are the basic plant organs?A leaf is a plant organ that grows from a stem. Photosynthesisusually occurs in leaves. Leaves come in many different sizes andshapes. They can even vary on the same plant. Each plant specieshas unique leaves or leaflike structures.A root is a plant organ that absorbs water and nutrientsdirectly from the soil. Roots contain tissues that transport thosenutrients to the stem. Roots anchor a plant to the ground. Someroots function as food storage.
Radishes and sweet potatoes aretwo examples of food storage structures in roots.A stem is a plant organ that provides support for growth. Thestem moves water from the roots to the leaves, and moves sugarsproduced in the leaves to the roots. The stem contains tissuesfor transporting food, water, and other materials from one partof the plant to another. Sometimes stems serve as organs for foodstorage. In green stems, chlorophyll-containing cells can carryout photosynthesis.READING ESSENTIALSCopyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.Adaptations in PlantsNameDateClassSection21.1Adapting to Life on Land, continuedMost of the plants you are familiar with, such as roses, ferns,ivy, pine trees, and maple trees, are vascular plants.
The stem contains vascular tissue. Vascular (VAS kyuh lur) tissue is made oftubelike, long cells through which water and nutrients travel.Plants that have vascular tissues are called vascular plants.There also are nonvascular plants such as mosses, hornworts,and liverworts. Nonvascular plants do not have vascular tissues.The body of a nonvascular plant is often only a few cells thick.Water and nutrients travel from cell to cell by the processes ofosmosis and diffusion.
(For a review of these processes, seeSection 6.2 for a discussion of diffusion and Section 8.1 for adiscussion of osmosis.)Vascular tissues were an important structural adaptation.Vascular plants can live farther away from water than nonvascularplants. Vascular tissues with thickened cells called fibers also allowvascular plants to grow taller than nonvascular plants.3.
What is vascular tissue?________________________________________________________________________Copyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.What is a seed?An important adaptation in some land plants wasthe development of seeds.
A seed is a plant organ thatcontains an embryo and a food supply covered in ahard protective coat. The seed protects the embryofrom drying out. Land plants reproduce by eitherEmbryospores or seeds. Remember that a spore is a reproducSeedtive cell that forms without fertilization and produces acoatnew organism. Spores have a hard outer wall and areFoodhaploid. Haploid cells contain only one of each kind ofsupplychromosome. Seeds are diploid since they contain twoof each kind of chromosome.In non-seed plants such as mosses and ferns, the sperm requirea film of water on the plant in order to reach the egg. In seedplants, which include all conifers and flowering plants, spermreach the egg without using a film of water. This is one reasonnon-seed plants require wetter habitats than most seed plants.What is alternation of generations in plants?The lives of all plants include two stages, or alternating generations. One generation is the gametophyte generation.
The othergeneration is the sporophyte generation. All cells of the gametophyte generation are haploid cells, including the gametes producedREADING ESSENTIALSChapter 21235NameDateClassSectionAdapting to Life on Land, continuedMalegamete (n)Femalegamete (n)Spores (n)GAMETOPHYTE (n)MeiosisFertilizationSPOROPHYTE (2n)Mitosis andcell divisionduring this generation. All cells of a sporophyte generation are diploid. The spores produced in the sporophyte generation, however,are haploid.In non-seed vascular plants such as ferns,spores are released into the environment.
Theygrow into haploid gametophyte plants. Theseplants produce male and female gametes. Afterfertilization, a sporophyte plant develops andgrows from the gametophyte plant.In seed plants such as sunflowers, sporesdevelop inside the sporophyte and become thegametophyte generation. The gametophytesare made up of only a few cells. Male andfemale gametes are produced by these gametophytes. This takes place within the sporophyteplant.
After fertilization, a new sporophytedevelops within a seed. The seed is releasedand the new sporophyte plant grows whenconditions are favorable.◗ After You ReadMini Glossarycuticle (KYEWT ih kul): protective, waxy coatingon the outer surface of most stems andleaves; important adaptation in reducingwater lossleaf: the plant organ that grows from a stem inwhich photosynthesis usually occursstem: plant organ that provides support andgrowth; contains tissues that transportfood, water, and other materials; organfrom which leaves grow. Can serve as foodstorage organ; green stems can carry outphotosynthesisnonvascular plant: plants that do not have vascular tissuesvascular plant: plants that have vascular tissues;enables taller growth and survival on landroot: plant organ that absorbs water and nutrients usually from soil; contains vascular tissues; anchors plant; can be a storage organvascular (VAS kyuh lur) tissue: tissues found invascular plants composed of tubelike, elongated cells through which food, water, andother materials are transported throughoutthe plantseed: a plant organ of seed plants consisting ofan embryo, a food supply, and a protectivecoat; protects the embryo from drying out236Chapter 21READING ESSENTIALSCopyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.21.1NameDateClassSection21.1Adapting to Life on Land, continued1.
Review the terms and their definitions in the Mini Glossary on page 236. Then on the linesbelow, explain how the development of the cuticle and seeds were adaptations to life on land.________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________2.
Choose one of the question headings in the Read to Learn section. Write the question in thespace below. Then write your answer to that question on the lines that follow.Question:Answer:____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________Copyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.____________________________________________________________________________________Visit the Glencoe Science Web site at science.glencoe.com to findyour biology book and learn more about adapting to life on land.READING ESSENTIALSChapter 21237NameDateClassSection21.2 Survey of the Plant Kingdom◗ Before You ReadSC.G.1.4.1 The student knows of the great diversity and interdependence of living things.SC.F.2.4.1 The student understands the mechanisms of asexual and sexual reproductionand knows the different genetic advantages and disadvantages of asexual and sexualreproduction.
Also covers SC.D.1.4.4Name or picture in your mind at least ten different plants. You might think of roses, cacti, ferns, oaktrees, and grasses to name a few. They are all plants, yet they look different from each other. As inthe other kingdoms you have studied, the plant kingdom has divisions based on shared characteristics. If you were to place plants in divisions, what characteristics would you use? Write your ideas forclassifying plants on the lines below.______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________◗ Read to LearnIdentify FactsAs you read this section, saythe name of each plant division aloud.
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