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PHYLUM ARTHROPODA Largest phylum of the animal kingdom Arthropod species account for ~ 75% of all animal species Evolved ~ 600 mya http://www.youtube.com/watch?v=h8DXzjvnzPk&feature=related Taxonomy General Characteristics All arthropods share three general characteristics: 1. Jointed appendages • • such as jointed legs and antennae arthropod actually means “jointed foot” General Characteristics 2. Exoskeleton • external skeleton that helps protect and support • has three layers – outer = wax to repel water and prevent from desiccating (drying out) – middle = protein + chitin + calcium carbonate for protection (like armour plating) – inner = protein + chitin, flexible protection (like chain mail) • limits maximum size of arthropods as exoskeletons become very heavy as the animal gets bigger • does not grow, must be molted and then re-grown General Characteristics 3. Segmented Body • Each segment generally contains at least 1 pair of appendages – Arthropod success is explained, in part, due to the diversity of their appendages • Legs • Antennae • Pincers and claws • Stingers • Wings • Jaws • Paddles • Gills • Spinnerets (for spinning webs) General Characteristics 3. Segmented Body • Sometimes different segments are fused together to form tagmata which may be specialized for – Feeding – Locomotion – Reproduction • Body structure often includes (especially all insects): – Head: arthropods are highly cephalized – Thorax – Abdomen Other Common Characteristics Open Circulatory System • Have a hemocoel = cavity containing internal organs – Hemolymph (essentially blood) is not contained in vessels, simply bathes the organs within the hemocoel Well Developed Nervous System • ladder-like – 2 ventral nerve cords (rails) linked by cross nerves (rungs) Well Developed Respiratory System • • Terrestrial arthropods have lungs or air sacs Aquatic arthropods have gills Taxonomy Taxonomy –Subphylum Trilobita An extinct subphylum characterized by: • • • very long antennae many segments hard exoskeleton Taxonomy –Subphylum Uniramia An extant (currently living) subphylum characterized by: • one-branched (or non-branched) appendages • have antennae and mandibles (jaws) • appear to have evolved on land Three Main Classes • Class Chilopoda – Centipedes with flattened body and 1 pair of legs per segment • Class Diplopoda – Millipedes with rounded body and 2 pairs of legs per segment • Class Insecta – Flies, grasshoppers, bees, wasps, ants, buttlerflies, moths and beetles that have madibles, antennae, unbranches appendages, 6 legs, and often one or two pairs of wings Taxonomy –Subphylum Chelicerata An extant (currently living) subphylum characterized by: • lack of antennae • Presence of pincer-like mouthparts called chelicerae Three Main Classes • Class Xiphosura – Horseshoe crabs • Class Arachnida – Spiders, scorpions, mites and ticks that have a cephalothorax and abdomen and 8 legs Taxonomy –Subphylum Crustacea An extant (currently living) subphylum characterized by: • two pairs of “feelers” on head • have branched appendages • mostly aquatic including copepods, water fleas, barnacles, crab, shrimp, crayfish, lobster • terrestrial exception – pill bugs/rolly-pollies Insects-Chapter 39 • • • http://www.youtube.com/watch?v=Na5ms4UxU0s http://www.youtube.com/watch?v=Mb3OQPT3qbU&feature=related http://www.youtube.com/watch?v=oWOC8trquFo&feature=related Classification of Insects • Phylum Arthropoda – Subphylum Uniramia •Class Insecta • Entomology = the study of insects • Entomologist = scientists that study insects Characteristics of Insects • Segmented body – divided into three tagmata: • Head • Thorax • Abdomen • Jointed appendages • Exoskeleton Characteristics of Insects • • • • • • Most insects are small They have jaws = mandibles One pair of antennae on head Thorax has three pairs of jointed legs Many species one or two pairs of wings Abdomen composed of 9-11 segments INSECT DOMINATION! • = 80% of all organisms that scientists have classified and named • inhabit almost every imaginable niche and ecosystem on the planet including the Arctic WHY INSECT DOMINATION? • exoskeleton • diverse jointed appendages • small • rapid and numerous reproduction • incomplete and complete metamorphosis Insects and People • The Negative Effects – crop damage – spread disease via bites •some fleas carry plague – damage buildings (Termites) – allergies to bites Insects and People The Positive Effects • Insects play vital role in almost all terrestrial and freshwater environments – Serve as food for many other animals • Cross pollinate plants – Estimated that insects pollinate 40% of worlds flowering plants • Provide us with: – honey – wax – silk