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Arthropods. Jointed-legged invertebrates. Arthropod Characteristics.
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Arthropods Jointed-legged invertebrates
Arthropod Characteristics • There are more species in the Phylum Arthropoda than in all the other animal phylums combined. (There are over 1 million species of arthropods that have been described. However the total number of arthropods may be as high as 1 billion billion.)
Arthropod Characteristics • Three characteristics shared by all arthropods are:1. exoskeleton2. segmented body 3. jointed appendages (which includes walking legs, claws, antennae, and wings.)
Exoskeleton • The exoskeleton provides protection from being eaten by animals and from drying out.-The exoskeleton can bend at the joints.-The exoskeleton is nonliving and cannot grow, so the animals must molt. • Molting is the shedding of the exoskeleton that occurs at regular periods as the arthropod grows.
Arthropod Characteristics • Open circulatory system (the blood is not contained within small tubes) • Blood is pumped from the heart into the space of the arthropods body • The blood of arthropods carries food but not oxygen throughout the body. • Complete digestive tract • They have any of 3 special respiratory organs: gills (Crab), book lungs (spider), or tracheal tubes (grasshopper)
Body Parts • They have 3 main body parts: 1. Head - first part of body and contains sense organs. 2. Thorax or chest - middle body part with walking legs attached. 3. Abdomen - last body part containing reproductive and digestive organs.
Metamorphosis • Metamorphosis is a series of distinct changes in form through which an organism passes as it develops from an egg to an adult. • Reduces competition between stages for • Food • Living space
Metamorphosis • Two types of metamorphosis: • Incomplete metamorphosis is where insects pass through 3 stages of development: • Egg (female lays eggs in a hole she has dug. • Nymph is an immature form that looks like a small adult. • Adult is an animal that has grown and developed enough to reproduce. example: grasshopper, cricket, termites, dragonflies
Complete metamorphosis is where insects pass through 4 stages in its development : • Egg • Larva is an insect in the worm like stage. Example: caterpillar, mealworm (Larva hatch from the egg and immediately begin eating a great deal and growing.) • Pupa is the third stage that occurs inside a cocoon. (Within the cocoon the tissues of the larva reorganize to form the adult insect.) • Adult example: most insects, butterfly, ants, bees, moths
Reproduction • Sexual Reproduction
Arthropod EVOLUTION
Taxonomy of Arthropods • 5 subphyla • Myriapoda (centipedes, millipedes) • Hexapoda (insects) • Chelicerata (Spiders, ticks) • Crustacea (Lobsters, Crabs) • Trilobita (all extinct)
Myriapoda • “myriapod”- means many-footed • 2 body parts • Head • Trunk- contains many paired appendages • Use tracheae for respiration
Myriapoda • 4 classes: • Class Chilopoda- centipedes • Class Diplopoda- millipedes • Class Pauropoda- pauropods • Class Symphyla- symphylans
Hexapoda • Six legs • 3 body parts- head, thorax and abdomen with appendages on head and thorax
Hexapoda • Classes: • Class Insecta-Beetles, Butterflies • Class Entognatha- Mayfly
Chelicerata • Horseshoe crabs, spiders, ticks and mites, scorpions, and sea spiders. • Have two main body parts • Cephalothorax – 6 pairs of appendages that include a pair of licerae (mouthparts), a pair of pedipalps, and 4 pairs of walking legs. • Abdomen • No antennae • Suck liquid food from prey
Chelicerata • 3 classes: • Class Merostomata- horseshoe crabs • Class Pycnogonida- Sea spiders • Class Arachnida- spiders, scorpions
Crustacea • Mainly marine, some freshwater and terrestrial • Two pairs of antennae (first antennae) • One pair of mandibles • Gills for respiration • 16-20 segments (some can have 60 or more)
Crustacea • 6 classes: • Class Remipedia- remipede • Class Cephalocarida- cephalocarid • Class Branchiopoda- daphnia, fairy shrimp • Class Ostracoda- copepod • Class Maxillopoda- fish louse • Class Malacostraca- lobsters, crabs, krill
Trilobita • They have been extinct for 200 million years. • Dorsoventrally flattened bottom dwellers • Scavengers • Could roll up their bodies • 2-67cm in length