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Chapter 28. Arthropods and Echinoderms. Arthropods. “ organism with a tough exoskeleton, jointed appendages and a segmented body”. Learning Targets 28.1 Identify the defining features of arthropods. Describe the important trends in arthropod evolution.
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Chapter 28 Arthropods and Echinoderms
Arthropods “organism with a tough exoskeleton, jointed appendages and a segmented body”
Learning Targets 28.1 • Identify the defining features of arthropods. • Describe the important trends in arthropod evolution. • Explain growth and development of arthropods
Exoskeleton • Exoskeleton made of chitin (a carbohydrate) • Can be tough and hard or soft and leathery
Tick Tough Exoskeleton
Spiny Lobster Tough Exoskeleton
Emperor gum mouth Catepillar Flexible, leathery exoskeleton
Some have dozens of segments while others have only 3 • Tough exoskeleton requires joints between segments and appendages to move
Feeding • Display all types • Mouthparts are modified to fit feeding behavior
Praying Mantis Carnivore
Lubber Grasshopper Herbivore
Respiration • Aquatic arthropods use gills • Horseshoe crabs use book gills • Spiders use book lungs • Terrestrial arthropods use tracheal tubes (supplies O2 by diffusion-muscles contract tube)
Book Gills/Lungs • Several sheets of tissue are layered like pages in a book (increases SA)
Internal Transport • Open circulatory system • Blood travels through heart to arteries to smaller vessels to sinuses and back to heart
Excretion • Terrestrial - excrete N waste through malpighian tubes (remove waste from blood and add to feces) • Aquatic - N waste removed by diffusion across gill surfaces • Some have glands near antenna
Diamond Beetle uses Malpighian tubes
Hermit Crab uses gills
Response • Well developed nervous system (All arthropods have a brain) • Large compound eyes (may have more that 2000 separate lenses!) • Some smell w/ antennae and use hair on legs to taste • Well developed hearing (ears in strange places like behind leg)
Compound eye Horsefly
Harlequin beetle long antennae as feelers
Stick grasshopper camoflauge Hoverfly Mimics bee Caterpillar markings as trick
Movement • Use well developed muscular system that is controlled by its nervous system which pulls and pushes against exoskeleton
Reproduction • Terrestrial arthropods have internal fertilization • Some Aquatic arthropods have external fertilization
Growth and Development • Tough exoskeleton protects but does not grow and must be shed (suit of armor) • Molting – arthropod sheds entire exoskeleton and produces larger one • (most molting involves metamorphosis which uses molting hormone) • Digests and eats/new skeleton is soft for up to a day
2 Types of Development • Complete • Incomplete
Complete Metamorphosis • 4 stages – egg, larva, pupa and adult • Involves interaction b/t molting hormone and juvenile hormone
Incomplete metamorphosis • Young look like adults without wings or sex organs • Gain these through gradual molts
28-2 A tour of Arthropods “Trilobites, Chelicerates, Crustaceans and Uniramians”
Learning Targets 28.2 • Explain how arthropods are classified • Identify the distinguishing features of the three subphyla of arthropods.
Trilobites • Chelicerae • Class Merostomata • Horseshoe Crabs • Class Arachnida • Spiders • Mites and Ticks • Scorpions • Crustacea • Uniramians • Centipedes • Millipedes • Insects
I. Trilobites • Now extinct • Hundreds of lenses in eye • Divided into many segments each with a walking leg.
II. Chelicerates • Chelicerates have mouthparts called chelicerae and two body sections and nearly all have four pairs of legs. • Ex) Horseshoe crabs, spiders, ticks and scorpions
2 part body • 1) Cephalothorax (contains legs, brain, mouth, eyes) • 2) abdomen (most of internal organs) • Specialized mouth parts = chelicerates and pedipalps • No antennae found in other arthropods
Used to grab prey Contain fangs which are used to stab and paralyze prey
Class MeristomataI. Horseshoe crab (Not so much a crab at all!) • Not dangerous • Tail for plowing through sand • Lysate in blood is used to test purity of medicines
B. Class Arachnida • Spiders, mites, ticks, scorpions, and daddy long legs • 4 pair of walking legs on cephalothorax • In addition they have chelicerae (sucking and biting) and pedipalps (holding prey)
1. Spiders • All are carnivores • Capture prey by pouncing or spinning webs with spinnerets (on abdomen) • Usually feed on insects (chelicerae-paralyzing venom-enzymes digest-suck) • Produce protein - silk
Interesting facts about spiders webs: • Whether or not they spin webs they produce silk • Spider silk is stronger than steel. • Web spinning spiders can spin webs almost as soon as they hatch!
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