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{Biology 112
Arthropods and Echinoderms
Includes animals such as crabs, spiders, and insects
Segmented bodies, a tough exoskeleton (external body covering) and jointed appendages (legs and antennae that extend from the body wall)
Fewer body segments than worms and highly specialized appendages used for feeding, movement and other functions
Most only have 2-3 segments Appendages include walking legs,
antennae, wings and mouthparts
Anthropods
Herbivores, carnivores and omnivores
Most receive gases through a network of tracheal tubes that extend throughout body Openings are called spiracles
Others have book lungs Aquatic organisms have gills Eliminate wastes through
structures called Malpighian tubules
internal fertilization (terrestrial) and external for aquaticFunctions of
Arthropods
Body Structure
Arthropods and Exoskeleton
Arthropods outgrow their skeletons and molt
The entire skeleton is shed and manufactures a larger one to take its place
Groups of Arthropods
Classification is based on number of segments and appendages – particularly mouthparts
Crustaceans (Crustacea)
Chelicerates (Chelicerata)
Uniramians (Uniramia)
Crustaceans
Crabs, shrimp, lobster, crayfish, barnacles
Two pairs of antennae, 2-3 body segments (head, thorax and abdomen), chewing mouthparts called mandibles
Chelicerates
Horseshoe crabs, spiders, ticks, and scorpions
Have mouthparts called chelicerae and 2 body segments
Four pairs of walking legs
Spiders spin webs of silk
Uniramians
Centipedes, millipeds and insects
Have jaws, one pair of antennae, unbranched appendages
Most body segments have one pair of legs each
Three body parts – head, thorax and abdomen Three pairs of legs attached to the thorax Usually, a pair of antennae, a pair of compound eyes,
and two pairs of wings Can detect changes in colour and movement Three pairs of appendages used for mouthparts Growth usually involves metamorphosis, the process of
changing shape and form Some are harmful to humans and others helpful The communicate using sound, chemical and other types
of signals Some are also capable of forming societies
Insects
Sea stars, sea urchins, and sand dollars Characterized by spiny skin, a water
vascular system, and suction-like structures called tube feet
Have an endoskeleton, five part radial symmetry as adults and are all deuterosomes
Contain a water vascular system that is filled with fluid that carries out much of its life functions
A maldreporite
Echinoderms