Reading Essentials for Biology Glencoe (794133), страница 59
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Identify What two divisions of plants have maleand female reproductivestructures on separateplants?________________________________________________________________________There are about 100 species of cycads today. They live in thetropics and subtropics. Cycads have male and female reproductivesystems on separate plants.
On the male plants, cones producepollen grains that produce motile (capable of movement) sperm.Cycads are one of the few seed plants that produce motile sperm.The female plant has cones that produce ovules. The trunks andleaves of many cycads look like palm trees. However, they are notclosely related because palms are anthophytes.Adaptations in GinkgophytaAdaptations in GnetophytaMost gnetophytes are found in the deserts or mountains ofAsia, Africa, North America, and Central or South America.There are three genera within Gnetophyta.
One is composed oftropical climbing plants. The second contains shrublike plants.This is the only gnetophyte genus found in the United States.The third genus is a strange-looking plant found only in SouthAfrica. The plant may live 1000 years. It grows close to theground and has a large root. It only has two leaves that continueto lengthen and curl as the plant grows older.Adaptations in ConiferophytaConifers are trees and shrubs with needlelike or scalelike leaves.They are a part of forests throughout the world and include pine,fir, spruce, juniper, cedar, redwood, yew, and larch.252Chapter 22READING ESSENTIALSCopyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.Today this division is represented by only one living species,Ginkgo biloba.
Like cycads, ginkgo male and female reproductivesystems are on separate plants. The male ginkgo produces pollengrains from cones that grow from the bases of leaf clusters. Likecycads, ginkgo pollen grains produce motile sperm. The femaleginkgo produces ovules which, when fertilized, grow fleshy,apricot-colored seed coats. These soft seed coats give off a badsmell if they are broken or crushed. Male ginkgoes are oftenplanted in cities because they tolerate smog and pollution.NameDateClassSection22.3Seed Plants, continuedThe reproductive structures of most conifers are produced incones. Most conifers have male and female cones on differentbranches of the same tree.
Male cones produce pollen. They aresmall and easy to overlook. Female cones are much larger. Theystay on the tree until the seeds have matured.Female coneWhy do conifers keep their leaves year-round?Most conifers keep their leaves for more than one year. Asleaves age or are damaged they drop to the ground.
The conifer,however, never loses all of its leaves at one time. For this reasonconifers are sometimes called evergreens.Plants that keep their leaves year-round can photosynthesizewhenever favorable conditions exist. This is an advantage wherethe growing season is short. Also, plants that keep their leavesyear-round do not use food reserves each spring to produce a newset of leaves.Evergreen leaves usually have a heavy coating of cutin, a waxy,waterproof material that helps reduce water loss. The shape ofconifer leaves, needlelike or scalelike, also helps reduce water loss.Male coneCopyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.Are all conifers evergreen?A few conifers, including larches and bald cypress trees, aredeciduous.
Deciduous plants drop all their leaves each fall orwhen water is scarce. Plants lose most of their water through theleaves. Very little water is lost through the bark or roots. It isan advantage to drop leaves in times of scarce water. However,without leaves, the plant cannot photosynthesize, and muststay dormant.3.
How does droppingleaves help keep a plantfrom losing water?________________________________________________________________________Adaptations in AnthophytaAll flowering plants are in the division Anthophyta. They arethe most well-known plants on Earth, with more than 250 000identified species. Like other seed plants, anthophytes have roots,stems, and leaves. Unlike other seed plants, they produce flowersand enclose seeds in a fruit.READING ESSENTIALSChapter 22253NameDateClassSection22.3Seed Plants, continuedA fruit develops from the female reproductive structure in aflower.
Sometimes other parts of the flower become part of thefruit. In pineapples, more than one flower is needed to developthe fruit. An advantage of fruit-enclosed seeds is the added protection the fruit provides for the embryo.Fruit aids in the spread of seeds. Animals eat the fruits or carrythem away to store for food. Seeds of some species that passthrough the animal’s digestive track unharmed are spread as theanimal wanders. In fact, some seeds have to pass through a digestive track before they can begin to grow a new plant. Brightlycolored fruit or fragrant fruit attracts birds and small animals.The large coconut floats, which allows it to spread far.What are monocots and dicots?Earlier you learned that seeds contain cotyledons, which storeor absorb food for the developing embryo. Now you will learnthat Anthophyta is divided into two classes.
They are named forthe number of cotyledons contained in the seeds. Monocotyledons________________________(mah nuh kah tuh LEE dunz) have one seed leaf. Dicotyledons(di kah tuh LEE dunz) have two seed leaves. They are often________________________called monocots and dicots.There is a simple way to tell theVascular Bundlesdifference between monocot andSeed Leavesin Leavesdicot plants: by examining theirMonocotsOne cotyledonUsually parallelleaves. Most monocot leaves haveveins that run parallel to each other,like the veins in a blade of grass or aleaf from a corn plant or a palm tree.Dicots, on the other hand, have veinsthat branch to form a network or looklike a net. Almost all trees, cacti,herbs, vegetables, wildflowers, andDicotsTwo cotyledonsUsually netlikegarden flowers are dicots.What is the life span of aplant?Why do some plants live longerthan people, and others live only afew weeks? The life span of a plant isgenetically determined.254Chapter 22READING ESSENTIALSCopyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.4.
How can you identify if aseed plant is a monocotor a dicot?NameDateClassSection22.3Seed Plants, continuedAnnual plants live for only one year or less. They sprout fromseeds, grow, reproduce, and then die. Most annuals have greenstems and do not have any woody tissue. Examples of annuals arecorn, peas, beans, as well as many of the weeds found in gardens.The seeds of annuals can survive drought and winter conditions.Biennial plants have two-year life spans. During the first year,biennials grow many leaves and develop a strong root system.Over winter, the part of the plant that is above ground dies back,but the roots remain alive. During the second spring, food storedin the roots is used to produce new shoots, flowers, and seeds.Examples of biennial plants are carrots, beets, and turnips.Perennials live for several years. They produce flowers andseeds periodically, usually once a year. Some survive harsh conditions by dropping their leaves or dying back to soil level.
Theirwoody stems and roots remain dormant. Examples of perennialsare columbine, strawberries, asparagus, and brambles.5. What is the name forplants that have a lifespan of more than twoyears?________________________________________________Copyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.Origins of Seed PlantsSeed plants first appeared about 360 million years ago duringthe Paleozoic Era. Ancient relatives of ginkgoes and cycads sharedthe forest with dinosaurs during the Mesozoic Era. About 65 million years ago, most members of Ginkgophyta died out alongwith other organisms during a mass extinction.Fossil evidence suggests that conifers emerged around 250 million years ago.
During the Jurassic Period, conifers became themost common forest plant, as they still are today. Anthophytesfirst appeared about 140 million years ago, late in the JurassicPeriod of the Mesozoic Era.6. Sequence Which of thefollowing best describesthe order in which plantslikely appeared on earth?(Circle your choice.)a.
anthophytes thenconifersb. conifers thenanthophytes◗ After You ReadMini Glossaryannual: anthophyte that lives for one year or lessbiennial: anthophyte that has a life span oftwo yearscotyledons (kah tuh LEE dunz): structure of seedplant embryo that stores or absorbs food forthe developing plantdeciduous plant: a plant that drops all of itsleaves each fall or when water is scarce orunavailable; an adaptation for reducingwater loss when water is unavailableREADING ESSENTIALSdicotyledon (di kah tuh LEE dun): class of anthophytes that have two seed leavesembryo: the young diploid sporophyte of a plantfruit: seed-containing ripened ovary of ananthophytemonocotyledon (mah nuh kah tuh LEE dun): classof anthophytes that have one seed leafChapter 22255NameDateClassSection22.3Seed Plants, continuedovule: in seed plants, the sporophyte structuresurrounding the developing female gametophyte; forms the seed after fertilizationperennial: anthophyte that lives for several yearspollen grain: in seed plants, structure in whichthe male gametophyte develops; consists ofsperm cells, nutrients, and a protectiveouter coating1.
Read the terms and definitions in the Mini Glossary above. Circle the three terms that categorize plants by their life spans. Write the terms on the lines below and provide two examples of plants for each category.________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________Copyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.2. Complete the diagram by writing in seven adaptations of seed plants.
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