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

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

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

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

Arachnids Arachnids- group of chelicerates that live on land – Eight legs – Fanglike pincers that inject venom – Silk glands

Uniramians Subphylum Uniramia or uniramians – Most species of all animals Uniramians have – Jaws, one pair of antennae, unbranched appendages Uniramians include – Centipedes – Millipedes – Insects

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?

Insects undergo metamorphosis Incomplete metamorphosis, insects look like miniature adults when they hatch There are three life stages of incomplete metamorphosis – Larva – Nymph – Adult

In complete metamorphosis, the insect changes form entirely There are three life stages of complete metamorphosis – Egg – Larva – Pupa – Adult

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

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

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

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

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

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

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

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

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