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 hosts 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 its 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 arthropods 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 dont 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 preys 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
