Reading Essentials for Biology Glencoe (794133), страница 78
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Name three arthropodsystems discussed in thissection.NameDateClassSection28.1Characteristics of Arthropods, continued1. Read the terms and definitions in the Mini Glossary on page 342. Then, circle a term thatdescribes a type of structural adaptation. On the lines below, write a sentence using the term.__________________________________________________________________________________________________________________________________________________________________________________________________________________________________________2. List the advantages and disadvantages of an exoskeleton in the web diagram below.AdvantagesDisadvantagesCopyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.ExoskeletonVisit the Glencoe Science Web site at science.glencoe.com to findyour biology book and learn more about characteristics of arthropods.READING ESSENTIALSChapter 28343NameDateClassSection28.2 Diversity of ArthropodsSC.D.1.4.4 The student knows that Earth’s systems and organisms are the result of a long, continuous change over time.SC.G.1.4.1 The student knows of the great diversity and interdependence of living things.◗ Before You ReadSpiders are arthropods.
They show many of the characteristics of arthropods, but they also are different from the arthropods you have learned about. On the lines below list what you have observedabout the behavior or appearance of spiders and how they are different from the arthropods youalready know about.______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________◗ Read to LearnIdentify CharacteristicsPoint to each part of thespider’s body in the illustration on page 345 as you readabout it.344Chapter 28Spiders, scorpions, mites, and ticks belong to the class Arachnida(uh RAK nud uh). Spiders are the largest group of arachnids.Spiders and other arachnids have only two body regions—thecephalothorax and the abdomen.
Arachnids have six pairs ofjointed appendages.The first pair of appendages, called chelicerae(chih LIH suh ree), is located near the mouth. Chelicerae areoften modified into pincers or fangs. Pincers hold food. Fangsinject prey with poison. Spiders do not have mandibles for chewing. Using a process of extracellular digestion, digestive enzymesfrom the spider’s mouth turn the internal organs of the prey intoliquid. The spider then sucks up the liquefied food.The second pair of appendages is called the pedipalps(PE dih palpz). Pedipalps are adapted for handling food and sensing. In male spiders, pedipalps carry sperm during reproduction.The four remaining appendages in arachnids are adapted as legs.Arachnids do not have antennae.Most people think of webs when they think of spiders. Althoughall spiders spin silk, not all make webs.
Spider silk is secreted bysilk glands in the abdomen. As silk is secreted, it is spun intothread by structures called spinnerets, located at the rear ofthe spider.READING ESSENTIALSCopyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.ArachnidsNameDateClassSection28.2Diversity of Arthropods, continuedB LegsA Simple eyesSpiders do not have compoundeyes. They have six or eightsimple eyes that, in most species,detect light but do not form images.A spider’s four pairsof walking legs arelocated on thecephalothorax.C CocoonFemale spiders wrap their eggsin a silken sac or cocoon, where theeggs remain until they hatch. Somespiders lay their eggs and never seetheir young. Others carry the sacaround with them until theeggs hatch.F CheliceraeCopyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.G PedipalpsA pair of pedipalps is usedto hold and move food andalso to function as senseorgans.
In males, pedipalpsare bulbous and are used tocarry sperm.Chelicerae are the two bitingappendages of arachnids. Inspiders, they are modifiedinto fangs with poison glandslocated near the tips.E Book lungsD Silk glandsGas exchange inspiders usuallytakes place inbook lungs.Spiders have seventypes of silk glands,which first releasesilk as a liquid. Thesilk then passes throughas many as 100 small tubesbefore being spun intothread by the spinnerets.What other animals are arachnids?Arachnida also includes ticks, mites, and scorpions. Ticks andmites have only one body section. The head, thorax, andabdomen are completely fused.
Ticks feed on blood from reptiles,birds, and mammals. They are small but can enlarge up to threetimes their normal size after feeding.Mites feed on fungi, plants, and animals. They are so smallthat they usually cannot be seen without magnification. Thebite of a mite can irritate the skin. Both mites and ticks canspread disease.Scorpions are easy to recognize because of their many bodysegments and large pincers. They have long tails with stingers atthe tips. They use the poison in their stingers to paralyze prey.Scorpions live in warm, dry climates. They eat insects and spiders.READING ESSENTIALS1. What animals, in additionto spiders, are included inArachnida?________________________________________________________________________Chapter 28345NameDateClassSection28.2Diversity of Arthropods, continuedCrustaceans2.
Name two landcrustaceans.________________________________________________Crustaceans (krus TAY shuns) are the only arthropods thathave two pairs of antennae for sensing. Some crustaceans havethree body sections, others have two. All crustaceans havemandibles for crushing food. Crustacean mandibles open andclose from side to side. Most crustaceans have two compoundeyes, often located on movable stalks.
Many crustaceans have fivepairs of walking legs. They also use the legs for seizing prey andcleaning other appendages. The first pair of walking legs is oftenmodified into strong claws for defense.Members of the class Crustacea include crabs, lobsters,shrimps, crayfishes, water fleas, pill bugs, and barnacles. Mostcrustaceans live in water. They use feathery gills to obtain oxygenfrom the water and to release carbon dioxide. Land crustaceans,such as sow bugs and pill bugs, must live where there is moisture.Moisture helps with gas exchange. They may be found in dampareas around building foundations.3.
How is gas exchange different between spidersand centipedes?________________________________________________________________________Centipedes belong to the class Chilopoda. Millipedes are members of the class Diplopoda. Like spiders, centipedes and millipedeshave Malpighian tubules for excreting wastes.
Unlike spiders, theyhave tracheal tubes rather than book lungs for gas exchange.Centipedes are carnivorous. They eat soil arthropods, snails,slugs, and worms. The bites of some centipedes are painful tohumans. A millipede eats mostly plants and dead material on theforest floor. Millipedes do not bite, but they can spray foulsmelling fluids from their stink glands. Millipedes walk with aslow, graceful motion.Horseshoe Crabs: Living Fossils4. Why are horseshoe crabsconsidered to be livingfossils?________________________________________________________________________346Chapter 28Horseshoe crabs are members of the class Merostomata.
Oneof the three living genera, Limulus, is found along the east coastof North America. Horseshoe crabs are considered to be livingfossils. Limulus has remained relatively unchanged since theTriassic Period about 220 million years ago.Horseshoe crabs are heavily protected by a large exoskeleton.They live in deep coastal waters.
Horseshoe crabs search on sandyor muddy ocean bottoms for algae, annelids, and mollusks. Thesearthropods migrate to shallow water in the spring, then mate atnight during high tide.READING ESSENTIALSCopyright © by Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.Centipedes and MillipedesNameDateClassSection28.2Diversity of Arthropods, continuedInsectsFlies, grasshoppers, lice, butterflies, bees, and beetles are a fewof the members of the class Insecta. Insects have three body segments and six legs.
There are more species of insects than allother classes of animals combined.How do insects reproduce?Insects usually mate once in their lifetime. The eggs are usuallyfertilized internally. Some insects reproduce from unfertilizedeggs, a process called parthenogenesis. In aphids, parthenogenesisproduces all-female generations. Most insects lay a large numberof eggs. This increases the chances that some offspring will survive long enough to reproduce. Many female insects are equippedwith an appendage that can pierce into wood or the surface of theground.
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