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Chapter 15 Section 3

Arthropods

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Objectives:

List the 4 main characteristics ofarthropods

Describe the different body parts of 4 kindsof arthropods

Describe the 2 types of metamorphosis ininsects

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Arthropods:

Have lived for hundreds of millions of years

Adapted to nearly every environment

Insects, spiders, crabs, and centipedes

Largest group of animals on Earth (75% ofall animal species)

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Characteristics ofArthropods:Segmented & specialized3 main body parts: head, thorax, abdomenStructures: wings, antennae, gills, pincers, claws

Jointed limbsArthro means joint, podmeans footEasier movement

External skeletonHard outer covering made of protein and chitinProtection, keeps from drying out

Sensing surroundings (well-developed nervoussystem)Eyes & bristles (sense organs)Compound eyes that detect light (identical light sensitive

units)

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Kinds of Arthropods:Classified by number of legs, eyes, and antennae

they haveAntennae is a feeler that senses touch, taste, or

smell

Kinds:Centipedes & Millipedes

Crustaceans

Arachnids

Insects

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Centipedes & Millipedes:One pair of antennae

Hard head

One pair ofmandibles (mouth parts)

Count legs in each segmentCentipedes: 30-354 legsMillipedes: up to 752!

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Crustaceans:Shrimps, barnacles, crabs, lobsters

Most live in water

Gills for breathing

Mandibles for eating

2 compound eyes

2 pairs of antennae

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Arachnids:Spiders, scorpions, mites, and ticks

2 main body parts: cephalothorax & abdomen

4 pairs of legs

No antennae

Mouthparts called: chelicerae

Simple eyes instead of compound eyes

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Arachnids continued

Spiders are more helpful than harmful

Ticks are parasites that live in forests andgrassy areasCarry diseases: Lymes diseaseSegments of body are joined as one small part

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Insects:Largest group of arthropods

3 main body parts

6 legs

2 antennae

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The World of Insects:Live on land, fresh water, and ocean surfaces

Many are helpful

Flowering plants depend on them for pollination

Some are pests that cause disease or destroy crops

Others pests are like mosquitoes and fleas

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Insect Bodies:3 parts: Head, thorax, abdomen

One pair of antennae

One pair of compound eyes

Mandibles

Each segment has one pair of legs

Some have wings

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Complete Metamorphosis:As an insect develops it changes form

4 main stages:Egg

Larva

Pupa

Adult

(*Butterflies, beetles, flies, wasps, and ants gothrough these changes)

http://fairmanstudios.com/images/complete_metamorphosis.jpg

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Incomplete Metamorphosis:Grasshoppers and cockroaches

Less complicated cycle

3 main stages:EggNymphAdult

Nymphs shed their exoskeleton (molting);like an adult but no wings and very small

http://www.vtaide.com/png/images/grasshopper.jpg

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Quick Quiz:The cephalothroax of a spider consists of a

head and a thorax (T/F)

The legs of most insects attach to the

abdomen (T/F)

Some types of insects live deep in oceanwaters (T/F)

The stages of complete metamorphosis areegg, nymph, and adult (T/F)