Reading Essentials for Biology Glencoe (794133), страница 65
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Read the terms and definitions in the Mini Glossary above. Then use the space below towrite a brief paragraph describing vegetative reproduction.____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________2. Use the table below to review what you have learned about the life cycle of mosses, ferns,and conifers.
Fill in the data table by entering “yes” or “no” in the appropriate space.MossFernConiferHas alternation of generationsFilm of water needed for fertilizationDominant gametophyteDominant sporophyteSporophyte is photosyntheticProduces seedsProduces spermProduces pollen grainsProduces egg3. Explain why mosses and ferns need a moist environment for sexual reproduction.________________________________________________________________________________________________________________________________________________________________________Visit the Glencoe Science Web site at science.glencoe.com to find yourbiology book and learn more about the life cycles of mosses, ferns, and conifers.282Chapter 24READING ESSENTIALSCopyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.TraitNameDateClassSection24.2 Flowers and Flowering◗ Before You ReadSC.F.1.4.7 The student knows that organisms respond to internal and external stimuli.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.Do you associate certain flowers with particular seasons or days in the year? When you think ofspring do you picture tulips? On the lines below identify the flowers and the particular seasons youassociate with those flowers.
After you read this section, you will understand why flowers bloom atcertain times of the year.______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________◗ Read to LearnCopyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.What is a flower?The process of sexual reproduction in flowering plants takesplace in a flower. The flower is a complex structure made up ofseveral organs.There are many sizes, shapes, and colors of flowers, yet all flowers share a basic structure.
A flower’s structure is genetically determined and is usually made up of four kinds of organs: petals, sepals,stamens, and pistils. You are probably most familiar with the petals.Petals are often the colorful structures at the top of a flower stem.The flower stem is called the peduncle. Sepals are green leaflikestructures that encircle the peduncle just below the petals.Inside the petals are the stamens.
A stamen is the male reproductive organ of a flower. The anther, at the tip of the stamen,produces pollen that eventually contains sperm.Attached to the peduncle, in the center of the flower, is one ormore pistils. The pistil is the female reproductive organ of theflower. The bottom portion of the pistil is the ovary. The ovary isa structure with one or more ovules. Each ovule usually containsone egg. The female gametophyte develops inside the ovule.A flower that has all four organs—sepals, petals, stamens, andpistils—is called a complete flower. A flower that lacks one ormore organs is called an incomplete flower.
Walnut trees haveseparate male and female flowers. The male flowers have stamensbut no pistils; the female flowers have pistils but no stamens. Themale and female flowers of walnut trees are incomplete flowers.READING ESSENTIALSIdentifyDetails As you read about aflower in the text, highlighteach part of the flower illustrated on page 284.Chapter 24283NameDateClassSection24.2Flowers and Flowering, continuedA PetalsThese are usually brightly colored andoften have perfume or nectar at theirbases to attract pollinators. In manyflowers, the petal also provides asurface for insect pollinators torest on while feeding.StigmaPetalsStylePistilOvaryAntherStamenB StamenPollen is produced in the antherat the tip of a thin stalk calleda filament.
Together, the antherand filament make up the stamen,the male reproductive organ. Thenumber of stamens in flowersvaries from none to many, likethe flower shown here.SepalPeduncleC SepalsA ring of sepals makes up theoutermost portion of the flower.Sepals serve as a protectivecovering for the flower bud.The female reproductive organ of aflower is the pistil. At the top of thepistil is the stigma that receives thepollen. The style is a slender stalkthat connects the stigma to the ovaryin which ovules grow.
Each ovulecan produce an egg. If fertilizationoccurs, the ovule develops into theseed. The number of pistils in flowersvaries from none to many.The flowers of sweet corn and grasses have other adaptations.Their flowers do not have petals and are adapted for pollinationby wind rather than by animals.PhotoperiodismIn summer, days are long and nights are short. In winter,days are short and nights are long. The length of daylight anddarkness each day affects plant growth and the timing of flowerproduction. For example, some chrysanthemum plants produceflowers only during the fall, when the length of daylight is gettingshorter and the length of darkness is getting longer each day.A grower who wants to produce chrysanthemum flowers in themiddle of summer must artificially increase the amount of darkness.
The grower can do this by placing a black cloth around theplants before the sun sets, and then removing it later the following morning. The response of flowering plants to daily daylightdarkness conditions is called photoperiodism.284Chapter 24READING ESSENTIALSCopyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.D PistilFilamentNameDateClassSection24.2Flowers and Flowering, continuedCopyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.What is the critical period?Plant biologists first thought that the length of daylight controlled flowering. Now they know it is the length of darknessthat controls flowering. Each plant species has specific daylightdarkness conditions that will make flowering start, known as thecritical period.
Plants can be placed in one of four categoriesdepending on the critical period they require to produce flowers.Plants are short-day plants, long-day plants, day-neutral plants,or intermediate-day plants.A short-day plant flowers when the number of daylight hoursis shorter than that of its critical period. Short-day plants usuallyflower sometime during late summer, fall, winter, or spring.Examples of short-day plants include asters, poinsettias, strawberries, ragweed, and pansies.A long-day plant flowers when the number of daylight hoursis longer than that of its critical period.
Long-day plants flower insummer. They also will flower if lighted continuously. Carnations,petunias, potatoes, lettuce, spinach, and wheat are long-day plants.As long as the proper growing conditions exist, day-neutralplants will flower over a range in the number of daylight hours.Examples of day-neutral plants are roses, cucumbers, cotton, andmany tropical plants, as well as dandelions and many other weeds.An intermediate-day plant will not flower if the days are longeror shorter than its critical period. Sugarcane and several grassesare in this category.1.
Analyze Which controlsflowering? (Circle yourchoice.)a. length of daylightb. length of darkness2. What are the four different categories of flowering plants withinphotoperiodism?________________________________________________________________________________________________How does photoperiodism benefit plants?Photoperiodism is a physiological adaptation. All the plants of aparticular species flower at the same time, ensuring that there is alarge population of pollinators. This is important because pollination is a critical event in the life cycles of all flowering plants.3.
How does photoperiodism ensure pollination?________________________________________________________________________READING ESSENTIALSChapter 24285NameDateClassSection24.2Flowers and Flowering, continued◗ After You ReadMini Glossaryanther: pollen-producing structure located atthe tip of a flower’s stamenphotoperiodism: flowering plant response todifferences in the length of night and dayday-neutral plants: plants that flower over arange in the number of daylight hourspistil: female reproductive organ of a flowerlong-day plants: plants that flower when thenumber of daylight hours is longer than itscritical periodovary: in plants, the bottom portion of aflower’s pistil that contains one or moreovules, each containing one eggpetals: leaflike flower organs, usually brightlycolored structures at the top of a stemsepals: leaflike, usually green structures thatencircle the top of a flower stem belowthe petalsshort-day plant: a plant that flowers when thenumber of daylight hours is shorter than itscritical periodstamen: male reproductive organ of a flowerconsisting of an anther and a filament1.
Read the terms and definitions in the Mini Glossary above. Highlight four terms that dealwith photoperiodism. Then circle the terms for the four organs that make up flowers.Copyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.2. Use the text and illustrations to list the organs and structures of a flower in the diagrambelow.(Female organ)Flower(Male organ)Visit the Glencoe Science Web site at science.glencoe.com to findyour biology book and learn more about flowers and flowering.286Chapter 24READING ESSENTIALSNameDateClassSection24.3 The Life Cycle of aFlowering PlantSC.F.2.4.1 The student understands the mechanisms of asexual and sexual reproduction and knows the differentgenetic advantages and disadvantages of asexual and sexual reproduction. Also covers SC.F.1.4.2◗ Before You ReadHave you ever opened the kitchen pantry or refrigerator and seen a potato or onion with leaves orroots growing from it? Why do you think that happens sometimes? Write your thoughts on thelines below.____________________________________________________________________________________________________________________________________________________________________________________________________________________________________◗ Read to LearnCopyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.The Life Cycle of an AnthophyteThe life cycle of flowering plants (anthophytes) and conifers issimilar.
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