Chapter 28Chapter 28Arthropods and Arthropods and EchinodermsEchinoderms

Phylum Arthropoda - ArthropodsPhylum Arthropoda - Arthropods

Largest and most successful Largest and most successful phylumphylum

75% of all animals!75% of all animals! Segmented bodySegmented body Tough exoskeletonTough exoskeleton Joint appendages (legs and Joint appendages (legs and

antennae)antennae) CephalizationCephalization Bilateral SymmetryBilateral Symmetry

ExoskeletonExoskeleton: an external covering : an external covering that protects and supports the bodythat protects and supports the body– Made from Made from chitinchitin– Varies in size, shape, and roughness. Varies in size, shape, and roughness.

Firm and leathery (caterpillars)Firm and leathery (caterpillars)Tough and hard (crabs and lobsters)Tough and hard (crabs and lobsters)Waxy (land dwelling arthropods)Waxy (land dwelling arthropods)

FeedingFeeding

FeedingFeeding– HerbivoresHerbivores– CarnivoresCarnivores– OmnivoresOmnivores– DetritivoresDetritivores– filter feedersfilter feeders– BloodsuckersBloodsuckers– parasites.parasites.– Mouth parts adapted to type of food Mouth parts adapted to type of food

eaten eaten Pincers, fangs, jawsPincers, fangs, jaws

• Terrestrial arthropods:Terrestrial arthropods: breathe through breathe through tracheal tracheal tubestubes

• Air enters and leaves Air enters and leaves tracheal tubes through tracheal tubes through spiraclesspiracles

• small openings located small openings located along the side of the body.along the side of the body.

Tracheal tubes

Tracheal tubes

Spiracles

RESPIRATION

•Book lungs organs that have layers of respiratory tissue (stacked like pages of a book.)

•Spiders, scorpions, horseshoe crabs

RESPIRATION CONTINUED…

Circulation and ExcretionCirculation and Excretion

Arthropods have a open Arthropods have a open circulatory circulatory systemsystem– A well developed heart pumps blood A well developed heart pumps blood

through arteriesthrough arteries

Malpighian tubules Malpighian tubules (terrestrial)(terrestrial):: saclike saclike organs that extract waste from the organs that extract waste from the bloodblood

Diffusion Diffusion (aquatic)(aquatic)

Response and ReproductionResponse and Reproduction

ResponseResponse– Well developed nervous systemWell developed nervous system– Brain serves as central switchboardBrain serves as central switchboard

ReproductionReproduction– Terrestrial arthropods: internal fertilizationTerrestrial arthropods: internal fertilization

Place sperm inside female OR deposit sperm packetPlace sperm inside female OR deposit sperm packet

– Aquatic arthropods: internal or external Aquatic arthropods: internal or external

Movement:Movement: Groups of well Groups of well developed muscles coordinate developed muscles coordinate movementmovement

– generating force by pulling on the exoskeletongenerating force by pulling on the exoskeleton– Muscles flex (bend) or extend (straighten) the Muscles flex (bend) or extend (straighten) the

joint.joint.

MOVEMENT

Growth and DevelopmentGrowth and Development

Arthropods will outgrow their exoskeleton Arthropods will outgrow their exoskeleton and undergo a period called and undergo a period called molting.molting.

Molting:Molting: the shedding of its entire the shedding of its entire exoskeleton exoskeleton – New/soft skeleton starting to formNew/soft skeleton starting to form– Controlled by the endocrine systemControlled by the endocrine system

28-2 Groups of Arthropods28-2 Groups of Arthropods

Classified by number of body Classified by number of body segments and mouth partssegments and mouth parts

3 major groups3 major groups1.1. Crustaceans Crustaceans

2.2. Spiders and their relativesSpiders and their relatives

3.3. Insects and their relativesInsects and their relatives

1) Crustaceans 1) Crustaceans (sub phylum Crustacea)(sub phylum Crustacea) Primarily aquaticPrimarily aquatic

– Includes crabs, shrimps, lobsters, crayfishes, Includes crabs, shrimps, lobsters, crayfishes, and barnacles.and barnacles.

– 2 pairs of antennae, two or three body 2 pairs of antennae, two or three body sections, and chewing mouthparts called sections, and chewing mouthparts called mandibles.mandibles.

Cephalothorax

Abdomen

Mandible

Antennae

Antennules

Body Plan of CrustaceansBody Plan of Crustaceans

CephalothoraxCephalothorax– Fusion of head with Fusion of head with

the thoraxthe thorax MandibleMandible::

– Mouthpart adapted Mouthpart adapted for biting and for biting and grinding foodgrinding food

swimmerets

Cheliped

•Cheliped: first pair of legs that have large claws modified to catch, pick up, crush, and cut food.

•Swimmerets: flipper-like appendages used for swimming

2) Chelicerates 2) Chelicerates (sub phylum Chelicerata)(sub phylum Chelicerata)

Horseshoe crabs, spiders, ticks, and Horseshoe crabs, spiders, ticks, and scorpionsscorpions– No antennaeNo antennae– Have mouthparts called cheliceraeHave mouthparts called chelicerae(stab and (stab and

paralyze) paralyze) & pedipalps & pedipalps (grab prey)(grab prey)

– 2 body sections2 body sections– 4 pairs of walking legs4 pairs of walking legs

Divided into 2 main classes: Divided into 2 main classes: MerostomataMerostomata (horseshoe crabs) (horseshoe crabs)ArachnidaArachnida (spiders, mites, ticks, and (spiders, mites, ticks, and

scorpions)scorpions)

Horseshoe crabsHorseshoe crabs

Horseshoe CrabsHorseshoe Crabs Appeared more than 500 million years ago Appeared more than 500 million years ago Have chelicerae, five pairs of walking legs, Have chelicerae, five pairs of walking legs,

and a long spike-like tail (telson) that is and a long spike-like tail (telson) that is used for movement.used for movement.

SpidersSpiders

Food and DigestionFood and Digestion– Spin webs of a strong, flexible protein Spin webs of a strong, flexible protein

called silkcalled silk– No jaws for chewingNo jaws for chewing

must liquefy food using enzymes must liquefy food using enzymes Use fanglike chelicerae to inject paralyzing Use fanglike chelicerae to inject paralyzing

venom venom

What does the spider use silk for?What does the spider use silk for?

Silk Silk glandsSpinnerets

Mites, Ticks, and ScorpionsMites, Ticks, and Scorpions

Mites and ticks are small arachnids that Mites and ticks are small arachnids that are often parasiticare often parasitic

Ticks can transmit bacteria that cause Ticks can transmit bacteria that cause serious diseasesserious diseases– chelicerae and pedipalps are specialized for chelicerae and pedipalps are specialized for

digging into a host’s tissues and sucking out digging into a host’s tissues and sucking out bloodblood

Scorpions inhabit warm areas around the Scorpions inhabit warm areas around the world.world.– Chew their prey Chew their prey

3) Uniramians3) Uniramians (sub phylum Uniramia) (sub phylum Uniramia) Centipedes millipedes, and insectsCentipedes millipedes, and insects Characteristics of UniramiansCharacteristics of Uniramians

– Have jaws, Have jaws, – One pair of antennaeOne pair of antennae– Un-branched appendagesUn-branched appendages– Live under rocksLive under rocks

Centipedes: one pair of legs on each Centipedes: one pair of legs on each segment; carnivoroussegment; carnivorous

Millipedes: two pairs of legs on each Millipedes: two pairs of legs on each segment; eat dead & decaying plant segment; eat dead & decaying plant mattermatter

28-3 Class 28-3 Class InsectaInsecta (Insects) (Insects)

Characteristics of Class Characteristics of Class InsectaInsecta– most species of any other animalsmost species of any other animals– Body divided into 3 segmentsBody divided into 3 segments

Head, thorax, and abdomenHead, thorax, and abdomen

Characteristics continued…Characteristics continued…

Segmented bodySegmented body ExoskeletonExoskeleton Jointed appendagesJointed appendages A typical insect also has:A typical insect also has:

a pair of antennae a pair of antennae a pair of compound eyes a pair of compound eyes two pairs of wings on the thoraxtwo pairs of wings on the thorax tracheal tubes that are used for respirationtracheal tubes that are used for respiration

ResponseResponse

Compound Eye: Compound Eye: made up of many lenses made up of many lenses – Detect minute changes in color and Detect minute changes in color and

movementmovement Chemical receptors for taste and Chemical receptors for taste and

smellsmell

Sensory hairs:Sensory hairs: detect movement in detect movement in surrounding air or watersurrounding air or water

Well developed earsWell developed ears

Feeding and Specialized Mouth Feeding and Specialized Mouth PartsParts

3 pairs of appendages that are used 3 pairs of appendages that are used as mouthparts, including a pair of as mouthparts, including a pair of mandiblesmandibles

Mandibles used to saw and grind food

Ant

Specialized mouth parts Specialized mouth parts continued…continued…

Spongelike mouthpart used to lap up food

Fly

Specialized Mouth PartsSpecialized Mouth Parts

Tubelike mouthpart used to suck nectar

Moth

Movement and FlightMovement and Flight

3 pairs of legs used for walking, 3 pairs of legs used for walking, jumping, capturing and holding prey.jumping, capturing and holding prey.– Legs have spines and hooks that are Legs have spines and hooks that are

used for grasping and defense.used for grasping and defense. Flying insects typically have two Flying insects typically have two

pairs of wings made of chitinpairs of wings made of chitin

MetamorphosisMetamorphosis

Process of changing shape and formProcess of changing shape and form– Insects undergo either incomplete Insects undergo either incomplete

metamorphosis or complete metamorphosis or complete metamorphosismetamorphosis

Incomplete MetamorphosisIncomplete Metamorphosis– Look very much like adult formLook very much like adult form– Immature forms are called nymphsImmature forms are called nymphs

lack functional sexual organs and wingslack functional sexual organs and wings

Complete MetamorphosisComplete Metamorphosis

Animals hatch into larvae that look Animals hatch into larvae that look and act nothing like their parentsand act nothing like their parents

Feed and grow rapidly and molt a Feed and grow rapidly and molt a few timesfew times

Undergo a final molt and change into Undergo a final molt and change into a pupaa pupa– stage in which an insect changes from stage in which an insect changes from

larva to adult.larva to adult.

INSECTS AND HUMANSINSECTS AND HUMANS

Contribute to richness of lifeContribute to richness of life Pollinate cropsPollinate crops Produce silk, wax, honeyProduce silk, wax, honey Considered a food delicacy in certain Considered a food delicacy in certain

countriescountries

Insect societiesInsect societies

Ants, bees, termites form insect Ants, bees, termites form insect societiessocieties– Same species that work together for the Same species that work together for the

benefit of the whole groupbenefit of the whole group A caste is within these societiesA caste is within these societies

– Individuals specialized for certain rolesIndividuals specialized for certain roles– Ex: queens (lay eggs), reproductive Ex: queens (lay eggs), reproductive

males, workersmales, workers

Communication in societiesCommunication in societies

Each society has its own “language”Each society has its own “language” Worker ants leave a pheromone trail Worker ants leave a pheromone trail

to guide her nest to food locationsto guide her nest to food locations Honey bees can communicate about Honey bees can communicate about

quality of food and directionquality of food and direction– 2 dances: round and waggle dance 2 dances: round and waggle dance

(close and far away)(close and far away)

Communication Continued…Communication Continued…

Round danceRound dance– Circle one way and then another.Circle one way and then another.– The more time they change direction The more time they change direction

the better quality of foodthe better quality of food Waggle danceWaggle dance

– Runs forwardRuns forward– Circles one wayCircles one way– Runs straight againRuns straight again– Circles the other wayCircles the other way