term definition arthropods hemolymph molting · and they both have a hard ... • crustacea, which...

Arthropods Name:_________________________________________Class:__________Date:____________Vocabulary

Term Definition

arthropods Invertebrateanimalswithjointedlimbs,asegmentedbody,andanexoskeletonmadeofchitin.

hemolymph Blood-likecirculatoryfluidofsomeinvertebrates.

molting Sheddingoftheoldshelltomakewayforanewgrowth.

What does this lobster have in common with a wasp?

Youmightnoticethattheirbodieshavesegments.Andtheybothhaveahardouterlayer.Becausetheysharetheseandotherfeatures,theyarebothclassifiedasarthropods. What are Arthropods?

Howoftendoyouthinkyouseeanarthropod?Well,haveyoueverlookedupcloseatanant?Aspider?Afly?Amoth?Withoveramilliondescribedspecies(andmanymoreyettobedescribed)inthephylumcontainingarthropods,chancesare,youencounteroneoftheseorganismseveryday,withoutevenleavingyourhouse.Arthropodsareaverydiversegroupofanimals.Infact,theyarethebiggestgroupofanimalsontheplanet,withupwardsof5milliondistinctspecies.Types of Arthropods

ArthropodsbelongtothephylumArthropoda,whichmeans“jointedfeet,”andincludesfourlivingsubphyla.

• Chelicerata,whichincludesspiders,mites,andscorpions.Intheseanimals,thefirstpairofappendagesareoftenmodifiedasfangsorpincers,andareusedtomanipulatefood.Spidershaveeightlegs.

• Myriapoda,whichincludescentipedesandmillipedes.Alloftheseanimalsliveonland,andcanhaveanywherefromtentonearly200pairsofappendages.

• Hexapoda,whichincludestheinsects.Theseanimalsdominatetheland.Allhexapodshavethreepairs(sixappendages)ofwalkingappendages.

• Crustacea,whichincludeslobsters,crabs,barnacles,crayfish,andshrimp.Theseanimalsdominatetheocean,andusuallyhaveasetofanteriorappendagesthataremodifiedasmandibles,whichfunctioningrasping,biting,andchewingfood.

Characteristics of Arthropods Characteristicsofarthropodsinclude:

1. Asegmentedbodywithahead,athorax,andabdomensegments.2. Appendagesonatleastonesegment.Theycanbeusedforfeeding,sensory

reception,defense,andlocomotion.Inadditiontolegs,antennasandmouthpartsareconsideredmodifiedappendages.

3. Anervoussystem.4. Ahardexoskeletonmadeofchitin,whichgivesthemphysicalprotectionandresistancetodryingout.In

ordertogrow,arthropodsshedthisoutercoveringinaprocesscalledmolting.

5. Anopencirculatorysystemwithhemolymph,ablood-likefluid.Aseriesofheartsmovethehemolymphintothebodycavitywhereitcomesindirectcontactwiththetissues.Hemolymphisinvolvedwithoxygendistribution.

6. Acompletedigestivesystemwithamouthandananus.7. Aquaticarthropodsusegillstoexchangegases.Thesegillshavealargesurfaceareaincontactwiththe

water,sotheycanabsorbmoreoxygen.8. Land-livingarthropodshaveinternalsurfacesthathelpexchangegasses.Insectsandmostother

terrestrialspecieshaveatrachealsystem,whereairsacsleadintothebodyfromporesintheexoskeleton.Theseporescoveralargepartoftheirexternalbodysurface.Othersusebooklungs,gillsmodifiedforbreathingair,asseeninspecieslikethecoconutcrab.Someareasofthelegsofsoldiercrabsarecoveredwithanoxygenabsorbingskin.Landcrabssometimeshavetwodifferentstructures:oneusedforbreathingunderwater,andanotherusedtoabsorboxygenfromtheair.

Summary

• Thearthropodsincludefourlivingsubphyla:chelicerates,includingspiders,mites,andscorpions;myriapods,includingcentipedesandmillipedes;hexapods,includinginsects;andcrustaceans.

• Arthropodsarecharacterizedbyasegmentedbody,ahardexoskeleton,andappendagesusedforfeeding,sensorystructures,defense,andlocomotion.

Review

1. Whatarethreeexamplesofarthropods?

2. Whatarethreedistinguishingfeaturesofthearthropods?

3. Describethearthropodcirculatorysystem.

4. Describehowinsectsobtainoxygen.