Reading Essentials for Biology Glencoe (794133), страница 70
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Read the terms and definitions in the Mini Glossary above. On the lines below, write a sentence using at least two of the terms from the Mini Glossary.____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________306Chapter 25READING ESSENTIALSCopyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.Mini GlossaryNameDateClassSection25.2Body Plans and Adaptations, continued2. Use the Venn diagram to compare and contrast acoelomate animals with pseudocoelomateanimals.
List characteristics of acoelomates in the left oval. List characteristics of pseudocoelomates in the right oval. List characteristics that both have where the ovals overlap.PseudocoelomateAcoelomateBothCopyright © 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 body plans and adaptations.READING ESSENTIALSChapter 25307NameDateClassSection26.1 Sponges◗ Before You ReadSC.F.1.4.2 The student knows that body structures are uniquely designed and adapted fortheir function. SC.F.2.4.1 The student understands the mechanisms of asexual and sexualreproduction and knows the different genetic advantages and disadvantages of asexualand sexual reproduction.Before you read this section, write down the characteristics of animals on the lines below. As youread, check to see whether sponges have all the characteristics of an animal.______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________◗ Read to LearnCreate a Quiz After youhave read this section, createa quiz based on what youhave learned.
After you havewritten the quiz questions, besure to answer them.Sponges are asymmetrical animals that live in water. Spongescan be brightly colored, shaped like balls or branches, smallerthan a quarter, or larger than a door. Sponges are invertebrates,which means they do not have backbones.
There are more than5000 species of sponges. Most live in marine or saltwater environments, but about 150 species live in freshwater.Sponges are mainly sessile organisms. Remember that sessileanimals permanently attach to a surface. Adult sponges do notmove in search of food. They get their food by a process calledfilter feeding. In filter feeding, an organism feeds by filteringsmall particles of food from water that passes by or through somepart of the organism.How are sponge cells organized?Like all animals, sponges are multicellular.
Their cells are differentiated to perform functions that help the sponges survive.The illustration on page 309 shows some of the different cells andtheir functions. Unlike most animals, sponges do not have tissues,organs, or organ systems.For some sponge species, a living sponge can be torn apart andthe cells would still be alive but separate from each other. Over aperiod of several weeks, the cells would come together, reorganizethemselves, and form new sponges.Many biologists hypothesize that sponges evolved from protists.An earlier chapter discussed protists that live together in colonies.The ancestors of sponges might have been colonial protists.308Chapter 26READING ESSENTIALSCopyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.What is a sponge?NameDateClassSection26.1Sponges, continuedOsculumA OsculumD Pore cellSurrounding each poreis a pore cell. Pore cellsallow water carryingfood and oxygen intothe sponge’s body.Water and wastes areexpelled through theosculum, the largeopening at the topof the sponge.Pore cellB Epithelial-like cellsEpithelial-likecellsThese cells are thin andflat.
They contract inresponse to touch or toirritating chemical. In sodoing, they close poresin the sponge.E AmoebocytesAmoebocyteCollar cellsDirection ofwater flowthrough poresCopyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.C Collar cellsLining the interior of thesponge are collar cells.Each collar cell has aflagellum that whips backand forth, drawing waterinto the sponge.Located between thetwo cell layers of asponge, amoebocytescarry nutrients toother cells, aid inreproduction, andproduce chemicalsthat help make up thespicules of sponges.F SpiculesThese small, needlelikestructures locatedbetween the cell layersof a sponge form thehard support systemsof sponges.SpiculesSponges show a major change in the evolution of animals—thechange from a unicellular life to a division of labor among groupsof organized cells.How do sponges reproduce?Sponges reproduce asexually and sexually.
Asexual reproductiondepends on the species of sponge. Asexual reproduction can be bybudding, fragmentation, or the formation of gemmules. A bud isREADING ESSENTIALS1. What organisms might bethe ancestors of sponges?________________________________________________________________________Chapter 26309NameDateClassSectionSponges, continued2. How does hermaphrodismbenefit sessile animals?________________________________________________________________________A Spermare releasedinto the water andcan travel to othersponges.an external growth on a sponge. If a bud drops off, it floats away,settles, and grows into a sponge.
Sometimes buds do not breakoff. Then a single sponge becomes a colony of sponges. Often,pieces or fragments of a sponge break off. They can grow intonew sponges.Some freshwater sponges produce seedlike particles, called gemmules. They are produced when the water temperature cools.
Theadult sponges die in winter, but the gemmules survive. In springwhen the water warms, the gemmules grow into new sponges.Most sponges reproduce sexually. Some sponges are separatesexes, but most sponges are hermaphrodites. A hermaphrodite(hur MAF ruh dite) is an animal that can produce both eggs andsperm.
In sessile animals, hermaphrodism increases the chancesthat fertilization will occur. During reproduction, sperm releasedby one sponge can be carried by water currents to fertilizeanother sponge.Fertilization in sponges can be external or internal. A fewsponges have external fertilization—fertilization that occurs outside the animal’s body. Most sponges have internal fertilization.This means the eggs inside the animal’s body are fertilized bysperm from another sponge. The sperm are carried into thesponge by water. Fertilization occurs and theresult is the development of free-swimmingB Fertilization islarvae. The larvae settleinternal. Fertilizedeggs develop intoand grow into adultzygotes.
Zygotessponges. A sponge isbecome freeable to move about onlyswimming larvae.during its larval stage.C The larvae swimfrom the body ofthe sponge oncurrents createdby collar cells.D A larva eventually settleson a surface and developsinto an adult that canreproduce.310Chapter 26What is theinternal structureof a sponge?Sponges are softbodied invertebrates.They have an internalstructure that givesthem support and canhelp protect them frompredators.
Somesponges have hard,sharp spicules locatedREADING ESSENTIALSCopyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.26.1NameDateClassSection26.1Sponges, continuedbetween the cell layers. Spicules may be made of glasslike materialor of calcium carbonate. Some species have thousands of tiny,sharp, needlelike spicules that make them difficult for animals toeat. Other sponges have an internal framework made of silica orspongin, a fibrous proteinlike material.
Sponges can be classifiedaccording to the shape of the spicules and frameworks and whatthey are made of.Some sponges contain chemicals that are toxic to fishes andother predators. Scientists are studying sponge toxins to identifythose that might be used as medicines.3. How are spongesclassified?________________________________________________________________________◗ After You ReadMini Glossaryexternal fertilization: fertilization that occursoutside the animal’s bodyhermaphrodite (hur MAF ruh dite): an animalthat can produce both eggs and spermfilter feeding: method in which food particlesare filtered from water as it passes by orthrough some part of the organisminternal fertilization: fertilization that occursinside the animal’s bodyCopyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.1.
Read the terms and definitions in the Mini Glossary above. On the lines below, explain whyfilter feeding is important for sessile animals.________________________________________________________________________________________________________________________________________________________________________2. Write a fact about sponges on the lines under each heading.SpongesObtain foodReproduceStructure1. _________________________1. _________________________1. _________________________2. _________________________Visit the Glencoe Science Web site at science.glencoe.comto find your biology book and learn more about sponges.READING ESSENTIALSChapter 26311NameDateClassSection26.2 CnidariansSC.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.
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