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Ch 28- Arthropods and Echinoderms biology: the science of life: world of animals | Discovery Education Phylum Arthropoda – Most diverse and successful animals of all time Inhabit air, land, water – Features are highly adapted Arthropods have – Segmented body parts – Tough exoskeleton (cuticle) made of chitin – Jointed appendages Classified based on number and structure of their body segments and appendages Major groups include – Crustaceans – Chelicerates – Insects
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Crustaceans Subphylum Crustacea – Evolved as marine arthropods Crustaceans share several common features – Two distinct body sections, cephalothorax and abdomen – One pair of appendages per segment – Two pairs of antennae – Exoskeleton – Carapace Appendages used for variety of functions – Collecting and manipulating food – Attracting females – protection
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Crustaceans Crustaceans vary in both anatomy and structure Types include – Decapods- lobsters and crabs have ten legs; largest group – Barnacles- sessile filter feeders wrapped in hard shell – Isopods- such as pill bugs have flattened bodies and seven pairs of legs – Tongue worms- parasites found in a host’s lungs or nasal passages
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Chelicerates There are three major groups of chelicerates – Horseshoe crabs- oldest living arthropods – Sea spiders – Arachnids- spiders, mites, ticks, and scorpions Chelicerates share several features – No antennae – Four pairs of walking legs – One pair each of chelicerae and pedipalps
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Arachnids Arachnids- group of chelicerates that live on land – Eight legs – Fanglike pincers that inject venom – Silk glands
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Uniramians Subphylum Uniramia or uniramians – Most species of all animals Uniramians have – Jaws, one pair of antennae, unbranched appendages Uniramians include – Centipedes – Millipedes – Insects
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Insects What are the distinguishing features of insects? – Body divided into 3 parts- head, thorax, and abdomen – 3 pairs of legs attached to thorax Why are insects so successful?
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Insects undergo metamorphosis Incomplete metamorphosis, insects look like miniature adults when they hatch There are three life stages of incomplete metamorphosis – Larva – Nymph – Adult
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In complete metamorphosis, the insect changes form entirely There are three life stages of complete metamorphosis – Egg – Larva – Pupa – Adult
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Echinoderms biology: the science of life: world of animals | Discovery Education Phylum Echinodermata Echinoderms have – Spiny skin – Internal skeleton – Water vascular system- What is it’s function? – Tube feet – Most exhibit 5-part radial symmetry Endoskeleton- an internal skeleton formed of hardened plates of calcium carbonate Live only in the sea Deuterostomes- animals in which the blastopore develops into an anus
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Types of Echinoderms There are five groups of echinoderms – Feather stars and sea lilies – Sea stars – Brittle stars and basket stars – Sea urchins, sea biscuits, and sand dollars – Sea cucumbers Some echinoderms can regenerate limbs or other body parts
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Metamorphosis Process of changing shape and form Under go either incomplete or complete metamorphosis Incomplete metamorphosis- immature forms of insects look very much like adults – Nymphs- immature forms of adult insects – Lack functional sexual organs and wings Complete metamorphosis- eggs hatch into larvae, look and act nothing like their parents and feed in different ways – Larva- look and act nothing like parents, feed in different ways and grow rapidly, molt a few times – Pupa- insect changes from larva to adult – Video -- World's Weirdest: Honey Bee Dance Moves -- National Geographic Video -- World's Weirdest: Honey Bee Dance Moves -- National Geographic
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Cephalothorax- formed by fusion of head with thorax Thorax-body part lies just behind head where most internal organs are Abdomen- posterior part of arthropod’s body Carapace- part of exoskeleton that covers cephalothorax Mandible- mouthpart adapted for biting and grinding food Chelipeds- first pair of legs, have large claws for catching, picking up, crushing, and cutting food Swimmerets- flipperlike appendages used by decapods for swimming Barnacles- sessile, no abdominal segments and don’t use mandibles – Attach themselves to rocks and marine animals
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Spiders and Their Relatives Subphylum Chelicerata- Chelicerates Horseshoe crabs, spiders, ticks, and scorpions 2 body sections- cephalothorax and abdomen 4 pairs of walking legs Lack antennae Book gills or book lungs Chelicerae- mouthpart that contains fangs, used for stabbing and paralyzing prey Pedipalps- long and modified for grabbing prey
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Horseshoe crabs- oldest living arthropods – Chelicerae – 5 pairs of walking legs – Long spikelike tail Spiders- largest group of arachnids – Spin silk webs – No teeth, paralyze prey and use digestive enzymes to break down prey’s tissue – Spinnerets- organs that contain silk glands – Video -- Black Widow: Most Venomous Spider in North America -- National Geographic Video -- Black Widow: Most Venomous Spider in North America -- National Geographic Mites and ticks- often parasitic – Chelicerae- needlelike structures used to pierce skin and suck blood Scorpians- widespread in warm areas – Pedipalps enlarged into claws – Venomous stinger – Chew prey using chelicerae
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Insects and their Relatives Subphylum Uniramia or uniramians- centipedes, millipedes, and insects Most species of all animals Jaws, one pair of antennae, unbranched appendages Centipedes- class Chilopoda – Few to 100 pairs of legs – One pair per body segment – Carnivores – Moist or humid areas Millipedes- class Diplopoda – 2 pairs per body segment – Feed on dead, decaying plant material
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Water vascular system- system of internal tubes, carries out many essential functions- respiration, circulation, movement Madreporite- sievelike structure through which water vascular system opens to outside Tube foot- structure that operates like suction cup, allows echinoderms to walk and pull open shells
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Groups of Echinoderms 7000 species of echinoderms Live in oceans Sea urchins and sand dollars, brittle stars, sea cucumbers, sea stars, sea lilies, and feather stars
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