Invertebrates 3
3What You Will Learnhave many specialized Invertebratesstructures that perform specialized functions.Organ systems perform basic lifefunctions in some invertebrates.Invertebrates have many methodsfor reproduction and development.Why It MattersStudying the characteristics of invertebrates will help you understand howthe same life function may be performed in different ways.Vocabulary segmentopen circulatory systemclosed circulatory systemmetamorphosisOutlining In your Science Journal,create an outline of the section. Usethe headings from the section in youroutline.InvertebratesKey Concept Invertebrates do not have backbones, butthey do have other structures to perform their life functions.Humans and snakes have them, but octopuses and butterfliesdon’t. What are they? Backbones! Most animals do not havebackbones. These animals are called invertebrates.Invertebrate CharacteristicsInvertebrates can be found in nearly every environment onEarth. Invertebrates also have many different shapes and sizes.For example, grasshoppers, clams, earthworms, and jellyfish areall invertebrates. Some invertebrates have heads, and others donot. Some invertebrates eat food through their mouths. Othersabsorb food particles through their tissues.The structures of invertebrates show how well adapted invertebrates are to their environment. For example, insects havedifferent kinds of wings that help them fly. Some invertebrateshave legs that help them burrow through the ground. Othershave strong bodies that help them swim. But all invertebratesare similar because they do not have backbones.Body SymmetryInvertebrate bodies have one of two kinds of symmetryor no symmetry at all. Sponges have irregular shapes and aretherefore asymmetrical. Jellyfish have radial symmetry. In animals that have radial symmetry, many lines can be drawnthrough the center of the body. Each line divides the animalinto opposite, or mirror images. Animals that have radial symmetry have only a top and a bottom.Most invertebrates have “two sides,” or bilateralsymmetry. A body with bilateral symmetry can bedivided into two parts by one vertical line. A linethrough the middle of the body divides the bodyinto nearly equal right and left halves. Animals withbilateral symmetry have a top and bottom, as wellas a front end and a back end. The developmentof a head is only seen in organisms with bilateralsymmetry, such as in the sea hare seen in Figure 1.Would you expect an animal withradial symmetry to have a head? Explain.7.5.aFigure 1 The Aplysia californicais a species of sea hare. Thismollusk has bilaterally symmetry.438
Figure 2Segmentation in Invertebrate BodiesAbdomenSegmentThoraxHeadSegmentationThe bodies of many animals are divided into sections orsegments. The body of the marine worm shown in Figure 2 hasmany nearly equal segments. The body of the insect shown inFigure 2 has three unequal segments. The insect has a head, athorax, and an abdomen. Segmentation in the body has manyadvantages. For example, each segment in an earthworm hasa set of muscles that help the earthworm push through soil.segment (SEG muhnt) any part of alarger structure, such as the body ofan organism, that is set off by naturalor arbitrary boundariesSupport of the BodyInvertebrate bodies need support and protection. Figure 3shows three invertebrates that have different kinds of support.The body of a sponge is supported by a jelly-like material andtiny, glassy structures. Other invertebrates have tough outercoverings. For example, round worms have thick skins, andlobsters have exoskeletons. These coverings are also importantbecause muscles that are attached to these coverings contractand relax to help invertebrates move.Why are outer coverings important for movementin animals?Figure 37.5.a7.2.a Students know the differences between thelife cycles and reproduction methods of sexual andasexual organisms.7.5.a Students know plants and animals have levelsof organization for structure and function, includingcells, tissues, organs, organ systems, and the wholeorganism.7.5.b Students know organ systems functionbecause of the contributions of individual organs,tissues, and cells. The failure of any part can affectthe entire system.7.5.g Students know how to relate the structures ofthe eye and ear to their functions.Support in Invertebrate BodiesSection 3Invertebrates439
Respiratory and Circulatory SystemsTracheaFigure 4 This beetle moves airinto its body and out of its bodythrough small holes along thesides of its body.All animals need oxygen to live. Animals take oxygeninto their bodies and release carbon dioxide from their bodiesthrough respiration. Respiration is performed by the respiratorysystem (RES puhr uh TAWR ee SIS tuhm). In lobsters, gills are themain organs that perform respiration. In insects, such as thebeetle in Figure 4, a network of tubes inside the body, calledtracheae (TRAY kee EE), performs respiration.Oxygen, carbon dioxide, and nutrients must be moved orcirculated throughout the body. The circulatory system transports many substances in a fluid called blood. Most molluskshave an open circulatory system. In open circulatory systems,blood moves through open spaces in the body. Invertebrates,such as annelids, have a closed circulatory system. In closedcirculatory systems, blood moves through tubes that form aclosed loop.What would happen to an insect if its tracheaebecame clogged?7.5.bDigestive and Excretory SystemsHuman MetamorphosisHow would you help a friendwho turned into a larva?Using pictures, describe thechanges that your friendwould go through. Go togo.hrw.com, and type in thekeyword HY7INVW.Animals obtain the energy they need by digesting food.Digestion is performed by the digestive system. Food is digestedas it is consumed and broken down. Any remaining materialis expelled from the body. Invertebrates have relatively simpledigestive systems. The mouth and anus form two ends of a tubecalled a digestive tract. The snail shown in Figure 5 has a stomach and other specialized areas along the digestive tract.As cells in the body use up nutrients, wastes are formed. Theexcretory system (EKS kruh TAWR ee SIS tuhm) eliminates thesewastes from cells with any excess water. In many invertebrates,the digestive tract also eliminates this kind of waste. Otherinvertebrates have separate excretory systems. These systemshave specialized organs to eliminate excess water and wastefrom cells.Figure 5 The digestive system inthe snail is made up of a digestivetract that has four parts: a mouth, astomach, an intestine, and an anus.StomachAnusIntestineMouth440Chapter 14Introduction to Animals
Figure 6Examples of Invertebrate Nervous inVentralnervecordBrainNervesNervecells formnerve netNervecordNervous SystemsThe nervous system is specialized for receiving and sending electrical signals that control all of the functions of thebody. Figure 6 shows examples of the nervous systems of threeinvertebrates. Many nervous systems have a specialized areacalled the brain. The brain acts as the control center. Nervoussystems also have specialized areas called sense organs. Senseorgans collect information, such as sound and light, from outside and inside the body. For example, eyes are organs thatsense light. When light enters the eye, signals are sent to thebrain. The brain interprets the signals as an image.open circulatory system(OH puhn SUHR kyuh luh TAWR eeSIS tuhm) a circulatory system inwhich the circulatory fluid is notcontained entirely within vesselsclosed circulatory system(KLOHZD SUHR kyuh luh TAWR eeSIS tuhm) a circulatory system inwhich the heart circulates bloodthrough a network of vessels thatform a closed loopQuick LabSeeing Like an Insect7.5.gInsects have a compound eye made up ofrepeating units. Each unit has its own lens.Try It!1. Use a ruler to draw a grid with dimensions of about 10 cm 10 cm on a sheetof tracing paper. The grid lines should beseparated by 0.5 cm.2. Place the grid over a black-and-whiteimage. Secure the grid with tape.3. Note the relative amount of black ink thatshows through in each box.4. Use a black marker to fill in the grid boxesthat are on top of an area that is mostlyblack. Don’t fill in the grid boxes that areabove squares that are mostly white.Think About It!5. Remove your grid, and examine it fromacross the room. Describe what you see?6. What part of the activity mimicked therepeating units in the eye of an insect?7. How might the curve of the insect eye further change how an insect sees images?20 minSection 3Invertebrates441
Reproduction and DevelopmentMany invertebrates reproduce asexually. One kind of asexual reproduction is called budding. Budding happens when apart of the parent organism develops into a new organism.The new organism then pinches off from the parent and livesindependently. The hydra, shown in Figure 7, reproduces bybudding. The new hydra is genetically identical to its parent. Fragmentation is a second kind of asexual reproduction.In fragmentation, parts of an organism break off and thendevelop into a new individual that is identical to the originalorganism. Certain organisms, such as flatworms called planaria,reproduce by fragmentation.Figure 7 Hydra reproduceby asexual reproduction. Theoffspring look similar to andare genetically identical tothe parent.metamorphosis (met uh MAWR fuhsis) a process in the lifecycle of manyanimals during which a rapid changefrom the immature organism to theadult takes placeComplete MetamorphosisMany insects reproduce sexually and lay eggs. As an insecthatches from an egg and develops, the insect changes formthrough a process called metamorphosis. Most insects go througha complex change called complete metamorphosis. As shown inFigure 8, complete metamorphosis has four main stages: egg,larva, pupa (PYOO puh), and adult. Butterflies, beetles, flies,bees, wasps, and ants go through this change.Compare the life cycle of a hydra with the lifecycle of a butterfly.Figure 87.2.aThe Stages of Complete Metamorphosise The adult butterfly pumps blood-like fluidinto its wings until they are full-sized. Thebutterfly is now ready to fly.d Adult body parts replacethe larval body parts.The adult splits itschrysalis and emerges.c After its final molt, the caterpillarmakes a chrysalis and becomesa pupa. The pupal stage may lasta few days or several months.During this stage, the insect isinactive.442Chapter 14Introduction to Animalsa An adult lays eggs. Anembryo forms insideeach egg.b A larva hatches from the egg.Butterfly and moth larvae arecalled caterpillars. The caterpillareats leaves and grows rapidly.As the caterpillar grows, it shedsits outer layer several times. Thisprocess is called molting.
AdultIncomplete MetamorphosisGrasshoppers and cockroaches are two kinds ofinsects that go through incomplete metamorphosis.Incomplete metamorphosis is less complicated thancomplete metamorphosis. As shown in Figure 9,incomplete metamorphosis has three main stages:egg, nymph, and adult. Some nymphs shed theirexoskeleton several times in a process called molting. An insect in the nymph stage looks very muchlike an adult insect. But a nymph does not havewings and is smaller than an adult. Through molting, the nymph develops into an adult.Review7.2.a, 7.5.a,7.5.b, 7.5.gSummary Invertebrate bodies are asymmetrical, have radial symmetry, or bilateral symmetry. The bodies of many invertebrates are divided intosegments. Invertebrates have protectiveouter coverings that providesupport and serve as a placefor muscles to attach.may have Invertebratesmany basic organ systems,such as a respiratory system,a circulatory system, a digestive system, an excretorysystem, a nervous system,and a reproductive system.reproduce Invertebratesasexually and sexually.Invertebrates develop fromembryos into larvae andfrom larvae into adults.EggsNymphNymphNymphFigure 9 The grasshopper nymphslook like smaller versions of the adult.8 Expressing Opinions Why are1 Describing Explain why respi-ration is important. Be sure toinclude an example of an invertebrate respiratory system.earthworms in a different groupthan roundworms? Explain.9 Applying Concepts Why can’tinsects see in complete darkness?2 Comparing How is the supportin the body of a sponge differentfrom the support in the body ofan insect?3 Identifying How do invert-ebrates remove wastes that areproduced by cells in their bodies?0 Making Calculations A seaurchin lost 12 of its 178 spinesin a storm. What percentage ofits spines does the sea urchinstill have?4 Comparing In the life cycle of agrasshopper, what are two maindifferences between nymphsand adults?5 Inferring If an animal hasa head, which kind of bodysymmetry would you expect theanimal to have?q Applying Concepts If thehead of an insect became stuckunderwater, would the insectdrown? Explain your answer.w Making Inferences What otherbody part do invertebrates thathave ears or noses have?6 Analyzing Processes Describemetamorphosis in the life cycleof a butterfly and in the life cycleof a grasshopper.7 Making Comparisons Com-pare an open circulatory systemand a closed circulatory system.Internet ResourcesFor a variety of links related to thischapter, go to www.scilinks.orgTopic: Sponges; EchinodermsSciLinks code: HY71443; HY70458443
Body Symmetry Invertebrate bodies have one of two kinds of symmetry or no symmetry at all. Sponges have irregular shapes and are therefore asymmetrical. Jellyfish have radial symmetry. In ani-mals that have radial symmetry, many lines can be drawn through the center of the body. Each li
2 Fun facts 80% of the world’s known species are invertebrates They form the basis of numerous food chains: e.g. 80% of plants rely on invertebrates for pollination One pipistrelle bat will eat around 8,000 insects in one evening. Some look very similar, some look very different. One thing they all
8. What do we call the animals which do not have bone structure or backbone? a. vertebrates b. invertebrates c. poriferans d. cnidarians 9. Snail, butterfly, bee, and clam are examples of invertebrates. This means that these animals possess this distinguishing characteristic. a. presence of backbone b. absence of backbone c. lack of cranium
Area 2: Population Ecology of grassland and wetland birds, reptiles and amphibians, small mammals and invertebrates Area 3: Community Ecology of Forest Vertebrates Area 4: Ecology of Coral Reefs and Intertidal Invertebrates Current Project: My current summer project is a comparison of reproductive biology and feeding habits of
Field Guide to Aquatic Invertebrates . This guide is designed to assist more experienced volunteer monitors with field identification of macroinvertebrates found in our rivers, streams and wetlands. General information is includ ed about the distinguishing features that aid in
ACTIVITIES. Math/Science Nucleus 1990,2000 2 LIFE CYCLE OVERVIEW OF THIRD GRADE ORGANISMS WEEK 1. . mollusk MATERIALS: books on land and marine invertebrates Internet BACKGROUND: Many groups of invertebrates have representatives that live in the oceans and
on uptake and toxicity of 21 different metals were reviewed by Phillips and Russo (1978) regarding marine and freshwater species. This review is short in studies on stream invertebrates, but it contains some information on 'rare' metals like Ni . although Cusimano et al. (1986) postulate
Student worksheet: Investigating Invertebrate Food Chains Student Vocabulary Words . hermit crab Una una algae & small invertebrates day & night true crabs Papa‘i algae, urchins, cowries day & night pond shrimp Opae ula algae, zooplankton, bacteria day & night 8 G5 U1 L4. G5 U1 OVR
Sponges Cnidarians Arthropods Roundworms Flatworms Annelids Mollusks Echinoderms To chordates Single-celled animal ancestor Multicellularity Tissues Radial symmetry Protostome development Radial symmetry Deuterostome Three germ layers, development bilateral symmetry Cladogram of Invertebrates What does the cladogram of invertebrates illustrate?
