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Arthropods Phylum Arthropoda Arthropods Largest and most successful phylum 75% of all animals! Segmented body Tough exoskeleton Joint appendages (legs and antennae) Cephalization Bilateral Symmetry Exoskeleton: an external covering that protects and supports the body – Made from chitin – Varies in size, shape, and roughness. Firm and leathery (caterpillars) Tough and hard (crabs and lobsters) Waxy (land dwelling arthropods) Evolution of Arthropods Evolution of Arthropods Typical primitive arthropod: – many identical segments with a pair of appendages. Evolution led to fewer segments and specialized appendages Fossilized Trilobites Feeding Feeding – Includes herbivores, carnivores, omnivores, detritivores, filter feeders, bloodsuckers, and parasites. – Mouth parts adapted to type of food eaten Pincers, fangs, jaws RESPIRATION • Terrestrial arthropods: breathe through tracheal tubes Spiracles • Air enters and leaves tracheal tubes through spiracles • small openings located along the side of the body. Tracheal tubes Tracheal tubes RESPIRATION CONTINUED… •Book lungs organs that have layers of respiratory tissue (stacked like pages of a book.) •Spiders, scorpions, horseshoe crabs Circulation and Excretion Arthropods system have a open circulatory No distinction between blood and other fluids Malpighian tubules (terrestrial): saclike organs that extract waste from the blood Diffusion (aquatic) Response and Reproduction Response – Well developed nervous system – Brain serves as central switchboard Reproduction – Terrestrial arthropods: internal fertilization Place sperm inside female OR deposit sperm packet – Aquatic arthropods: internal or external Reproduction Separate sexessexual reproduction Males directly transfer sperm to females Ex. Barnacle stretches out appendage to local females Mating occurs after female molts MOVEMENT Movement: Groups of well developed muscles coordinate movement – generating force by pulling on the exoskeleton – Muscles flex (bend) or extend (straighten) the joint. Growth and Development Arthropods will outgrow their exoskeleton and undergo a period called molting. Molting: the shedding of its entire exoskeleton – New/soft skeleton starting to form – Controlled by the endocrine system – Molting Cicada Video – http://upload.wikimedia.org/wikipedia/c ommons/6/62/Cicada_molting_animate d-2.gif Groups of Arthropods Classified by number of body segments and mouth parts 3 major groups 1. Crustaceans 2. Spiders and their relatives 3. Insects and their relatives 1) Crustaceans Primarily aquatic – Includes crabs, shrimps, lobsters, crayfishes, and barnacles. – 2 pairs of antennae, two or three body sections, and chewing mouthparts called mandibles. Abdomen Cephalothorax Antennae Antennules Mandible Body Plan of Crustaceans swimmerets Cheliped Cephalothorax – Fusion of head with the thorax Mandible: – Mouthpart adapted for biting and grinding food •Cheliped: first pair of legs that have large claws modified to catch, pick up, crush, and cut food. •Swimmerets: flipperlike appendages used for swimming 1) Small Crustaceans Copepods- extremely abundant, planktonic, filter feed Barnacles- usually sessile, filter feed, body enclosed by calcareous plates Krill- planktonic, shrimp-like, have carapace to cover anterior, filter feed True Crabs Small abdomen and tucked under cephalothorax V-shape ab. in males U-shape ab. in females Largest and most diverse of decapods Scavengers and predators Male Jonah Crab Female Jonah Crab 2) Chelicerates Horseshoe scorpions crabs, spiders, ticks, and – No antennae – Have mouthparts called chelicerae – 2 body sections – 4 pairs of walking legs Divided into 2 main classes: Merostomata (horseshoe crabs) Arachnida (spiders, mites, ticks, and scorpions) Horseshoe crabs Horseshoe Crabs Appeared more than 500 million years ago – changed little since that time. Have chelicerae, five pairs of walking legs, and a long spike-like tail (telson) that is used for movement. Horseshoe Crab 1. Carapace 2. Telson 3. Compound eye 4. Anterior spine Five pair of legs Spiders Food and Digestion – Spin webs of a strong, flexible protein called silk – No jaws for chewing must liquefy food using enzymes Use fanglike chelicerae to inject paralyzing venom What does the spider use silk for? Silk glands Spinnerets Mites, Ticks, and Scorpions Mites and ticks are small arachnids that are often parasitic Ticks can transmit bacteria that cause serious diseases – chelicerae and pedipalps are specialized for digging into a host’s tissues and sucking out blood Scorpions inhabit warm areas around the world. – Chew their prey 3) Uniramians Centipedes, millipedes, and insects Characteristics of Uniramians – Have jaws – One pair of antennae – Un-branched appendages – Carnivores Class Insecta (Insects) Characteristics of Class Insecta – Contains most species of any other animals – Body divided into 3 segments Head, thorax, and abdomen Characteristics continued… Segmented body Exoskeleton Jointed appendages A typical insect also has: a pair of antennae a pair of compound eyes two pairs of wings on the thorax tracheal tubes that are used for respiration Response Compound Eye: made up of many lenses – Detect minute changes in color and movement – Information from eye is assembled in the brain and directs the insects response Chemical receptors for taste and smell – Located on the mouthparts, antennae, and legs Sensory hairs: detect movement in surrounding air or water Well developed ears Feeding and Specialized Mouth Parts 3 pairs of appendages that are used as mouthparts, including a pair of mandibles Ant Specialized mouth parts continued… Spongelike mouthpart used to lap up food Fly Specialized Mouth Parts Tubelike mouthpart used to suck nectar Moth Movement and Flight 3 pairs of legs used for walking, jumping, capturing and holding prey. – Legs have spines and hooks that are used for grasping and defense. Flying insects typically have two pairs of wings made of chitin Metamorphosis Process of changing shape and form – Insects undergo either incomplete metamorphosis or complete metamorphosis Incomplete Metamorphosis – Look very much like adult form – Immature forms are called nymphs lack functional sexual organs and wings Complete Metamorphosis Animals hatch into larvae that look and act nothing like their parents Feed and grow rapidly and molt a few times Undergo a final molt and change into a pupa – stage in which an insect changes from larva to adult.
