Reading Essentials for Biology Glencoe (794133), страница 73
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It is used to takefood into the planarian’sdigestive system.D Flame cellsExcess water is removed from the planarian’sbody by a system of flame cells. The waterfrom flame cells collects in tubules andleaves the body through pores on thebody surface.ExtendedpharynxNucleusFlamecellDigestive tractCiliaE CiliaHairlike cilia arelocated on the ventralsurface of planarians.Cilia help the worm to pullitself along. Planarianlocomotion results fromthe movement of cilia.CiliaExcretorysystemThe knob-shaped head of a tapeworm is called a scolex(SKOH leks).
The tapeworm’s body is made of detachable, individual sections called proglottids. A proglottid (proh GLAH tihd)contains muscles, nerves, flame cells, and male and femalereproductive organs. Some adult tapeworms that live in animalintestines can be more than 10 m in length and consist of2000 proglottids.320Chapter 26READING ESSENTIALSCopyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.MouthNameDateClassSection26.3Flatworms, continuedWhat are flukes?A fluke is a parasitic flatworm that spends part of its life in theinternal organs of a vertebrate, such as a human.
The fluke feedson cells, blood, and other fluids of the host organism. Flukes havecomplex life cycles. They can require more than one host. Thehost can be a vertebrate or invertebrate. For example, bloodflukes of the genus Schistosoma cause a disease in humans knownas schistosomiasis. The disease is common where rice is grown.Farmers plant and harvest rice in standing water.
Refer to the illustration below to understand the life cycle. Blood flukes are common where the secondary host, snails, also are found.3. Flukes only use one hostin their life cycle. (Circleyour choice.)a. Trueb. FalseA Adult flukes are about 1 cm long andThe Life Cycle of the Flukelive in the veins of the human digestivetract. Fluke embryos that are encasedin a protective capsule pass out of thebody with human wastes.
If they reachfreshwater, they hatch.EmbryosreleasedCopyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.D When a human walks throughwater with bare feet or legs,fluke larvae can bore throughthe skin, enter the bloodstream, and move to theintestine, where theymature. Fertilizationoccurs and embryospass out of the intestine and the cycle canbegin again.HumanhostLarvaB Free-swimming larvaedevelop from embryosand enter their snail hosts.C Larvae develop inside the snailand asexually reproduce. Newlarvae leave the snail andenter the water.Snail hostLarvaREADING ESSENTIALSChapter 26321NameDateClassSection26.3Flatworms, continued◗ After You ReadMini Glossarypharynx (FAHR inx): in planarians, the tubelike,muscular organ that extends from themouth; aids in feeding and digestionproglottid (proh GLAH tihd): a section of a tapeworm that contains muscles, nerves, flamecells, and reproductive organsregeneration: replacement or regrowth of missing body partsscolex (SKOH leks): knob-shaped head of atapeworm1.
Read the terms and definitions in the Mini Glossary above. In your own words explainwhy regeneration is considered asexual reproduction. Write your explanation on thelines provided.____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________PlanariaCopyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.2.
Use the Venn diagram to compare planarians to tapeworms. List facts that describe planarians in the left oval. List facts that describe tapeworms in the right oval. List facts thatdescribe both planarians and tapeworms where the ovals overlap.TapewormBothVisit the Glencoe Science Web site at science.glencoe.comto find your biology book and learn more about flatworms.322Chapter 26READING ESSENTIALSNameDateClassSection26.4 RoundwormsSC.G.1.4.1 The student knows of the great diversity and interdependence of living things. Also covers SC.F.2.4.1◗ Before You ReadHealth care professionals often say that one of the best ways to prevent illness is to frequently washyour hands.
Think of reasons why washing your hands helps prevent illness. Write those reasons onthe lines below. After you read this section, list one disease from this section that can be preventedby frequent hand washing. You will have to infer the information from your reading.________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________◗ Read to LearnCopyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.What is a roundworm?Roundworms belong to the phylum Nematoda.
They live insoil, inside animals, in freshwater, and in marine environments.There are more than 12 000 species of roundworms. Someroundworm species are free-living, but many are parasitic. Nearlyall plant and animal species are affected by parasitic roundworms.Roundworms are tapered at both ends. They have a thickouter covering that protects them in harsh environments. Theyshed the outer covering four times as they grow. Roundwormslook like tiny, wriggling bits of thread. They do not have circularmuscles but they do have lengthwise muscles.
As one musclecontracts, another muscle relaxes. Roundworms move in a thrashing fashion due to the alternating contraction and relaxation ofthe muscles.Roundworms have a pseudocoelom, a fluid-filled bodycavity partly lined with mesoderm. They are the simplestanimals with a tubelike digestive system. Unlike flatworms,roundworms have two body openings—a mouth and ananus. The free-living species have well-developed senseorgans, such as eyespots. These are less-developed in theparasitic forms.READING ESSENTIALSMake Flash Cards For eachpage, think of two questionsa teacher might ask on a test.Write the question on oneside of the flash card.
Thenwrite the answer on the otherside. Quiz yourself until youknow the answers.RoundwormChapter 26323NameDateClassSection26.4Roundworms, continued1. Infer Why are childrenmore likely than adults tobe infected by certaintypes of roundworms?________________________________________________________________________________________________2. Other than humans, whatorganisms can roundworms infect?________________________________________________________________________324Chapter 26About half of roundworm species are parasites.
There are about50 species that infect humans. Worldwide, the most commonroundworm infection is from Ascaris (ASS kuh ris). It is more common in tropical and subtropical areas. Children become infectedmore often than adults. Eggs of Ascaris are found in soil. Theyenter the human body through the mouth. The eggs hatch in theintestines. Ascaris moves into the bloodstream and then into thelungs. They are coughed up, swallowed, and the cycle begins again.Pinworms are the most common roundworm parasite in theUnited States.
Children are infected more than adults. Pinwormsare highly contagious because eggs can survive on surfaces up totwo weeks. The life cycle begins when live eggs are ingested.They mature inside the intestinal tract of the host. Female pinworms exit through the host’s anus—usually as the host sleeps—and lay eggs on nearby skin. These eggs fall onto bedding ornearby surfaces.Trichinella causes a disease called trichinosis (trih keh NOH sis).The roundworm enters through the mouth if an individual eatsinfected pork or wild game that is raw or undercooked.Hookworm infections are common in humans in warm climateswhere they walk on contaminated soil in bare feet.
Hookwormscause people to feel weak and tired due to blood loss.Can roundworms infect other organisms?There are about 1200 species of nematodes (roundworm parasites) that cause disease in plants. They are particularly attractedto plant roots, causing a slow decline of the plant. Nematodescan infect fungi and form symbiotic associations with bacteria.Nematodes have been used to control pests. Instead of usingchemical pesticides, nematodes can be introduced to kill weevilsthat damage plants.READING ESSENTIALSCopyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.Diversity of RoundwormsNameDateClassSection26.4Roundworms, continued◗ After You ReadMini Glossarytrichinosis (trih ken NOH sis): a disease caused by the roundworm Trichinella that can be ingested inraw or undercooked pork, pork products, or wild game1.
Read the term and definition in the Mini Glossary above. Use the term in a sentence thatexplains how a person might contract this disease. Write your sentence on the lines below.____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________Copyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.2. Use information from this section to fill in the table below.Name ofanimalExamplesRoundwormsAscarisOne or twoopenings inbody?Do they liveon land or inwater?Do they havesensoryorgans?Are anyspeciesparasitic?Visit the Glencoe Science Web site at science.glencoe.comto find your biology book and learn more about roundworms.READING ESSENTIALSChapter 26325NameDateClassSection27.1 MollusksSC.G.1.4.1 The student knows of the great diversity and interdependence of living things.
SC.F.1.4.2 The studentknows that body structures are uniquely designed and adapted for their function. Also covers SC.F.2.4.1◗ Before You ReadSnails and earthworms live in different places and have different habits. However, both move efficiently, if somewhat slowly. What questions do you have about the movement and body systems ofthese two animals? Write your questions on the lines below. After you have read this section, answerthe questions that you have written.______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________◗ Read to LearnCompare andContrast As you read thissection, use one color to highlight the ways in which allmollusks are the same.
Useanother color to highlightways in which mollusks differfrom each other.1. What five characteristicsdo mollusks have incommon?________________________________________________Snails, slugs, squid, octopuses, and some other animals thatlive in shells either in the ocean or on the beach are mollusks.Members of the phylum Mollusca, or mollusks, include bothslow-moving slugs and fast, jet-propelled squid. Some mollusks,like snails and slugs, live in damp areas on land.
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