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Ch.18, 19 and 20. Phylum Arthropoda. Arthropoda. The most diverse and numerous of all animal phyla Joint-foot 900,000 species More beetles than all vertebrates(species). Evolution of Arthropods. Natural selection Fewer body segments Specialized appendages
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Ch.18, 19 and 20 Phylum Arthropoda
Arthropoda • The most diverse and numerous of all animal phyla • Joint-foot • 900,000 species • More beetles than all vertebrates(species)
Evolution of Arthropods • Natural selection • Fewer body segments • Specialized appendages • Tagmata – head , thorax, abdomen • Cephalothorax, abdomen
Phylum Arthropoda • 4 subphyla • Trilobita-extinct • Chelicerata-chelicerae-2 body segments – 4 pairs of walking legs • Crustacea-2 pair antennae-mandibles • Uniramia-jaws-one pair of antennae-unbranched appendages-3 pairs
Arthropoda • Cambrian period • 570 million years ago • Exoskeleton developed • Molting/hormonal control • Hydrostatic skeleton lost – replaced by open system
Annelids-Arthropods • Shared ancestor • coelom • Segmented body • Open circulatory system
Cephalization – eyes, fused ganglia, antennae(fiirst to form images) Metemerism – somites are very specialized Paired jointed appendages Exoskelton Complex social structures Protective coloration Common Characteristics
Bilateral symmetry Head, thorax, tail Cephalothorax, abdomen Complete digestive system Respiration – body surface, gills, tracheael tubes or book lungs Air enters through spiracles Paired excretory glands- malpighian tubules Characteristics
Nervous system • Brain • Well developed system • Compound eyes 2000 separate lenses • Color and motion
Versatile Exoskeleton • Cuticle secreted by the epidermis • Made of several layers secreted during molting • Exocuticle first then endocuticle • Layers made of chitin • Tough resistant nitrogenous polysaccharide
Insoluble in water and weak acids • Protection, coloration, movement • To grow must shed the exoskeleton or molt • Limits body size – no giant arthropods
Segmentation • Each somite – jointed appendages • Often modified • Hollow levers that are moved by internal muscles • Sensory hairs – modified for sensory functions, food handling, swift walking and swimming
Air piped directly to cells • Efficient tracheal system of air tubes • Oxygen delivered directly to tissues and cells • Makes high metabolic rate possible • Limits body size • Some use gills
Complex behavior patterns • Inate controls most activities • Some learning • Complex societies and division of labor
Metamorphosis • Larval state to adult stage • Adapted for different ecological niches • Less competition among the species • Incomplete or Complete
Reproduction • Sexes usually separate • Internal fertilization • Live, eggs, eggs inside or attached
Trilobita • Before Cambrian period • 200 million years ago • Abundant during the Cambrian and Ordovician periods • Trilobed shape of body • Bottom dwelling scavengers • Could roll like pill bugs
Chelicerata • Horseshoe crabs • Spiders • Ticks • Mites • Scorpions and sea spiders • Name for mouth parts called Chelicerae
Merostomata Pycnogonida Arachnida Horseshoe crabs Sea spiders Scorpions, spiders, ticks, mites 3 classes
Characteristics • 6 pairs of appendages • 1 pair of chelicerae – suck liquid from prey • Pedipalps • 4 pairs of walking legs • No mandibles • No antennae
Subphylum Crustacea • 5 classes • Lobster • Crab • Shrimp • Pill bug or sow bug - terrestrial • Named after hard outer shell
Uniramia • 5 classes • Chilopoda – centipedes • Diplopoda – millipedes • Pauropoda – small soft bodied myriads • Symphyla – small centipede like animals • Insecta – grasshopper to bumble bee to beetle
200 million insects for every singe human • Evolved wings 250 million years before reptiles