Transcript Arthropods
Arthropods Chapter 28 What is an Arthropod? Characteristics: Invertebrate animals with bilateral symmetry A coelom Exoskeleton Joint appendages Appendages Are anything like legs, antenna that grows out of the body Are adapted for sensing, walking, feeding & mating Arthropods were 1st to evolve jointed appendages Appendages Allows for more powerful movements Different uses ex: spiders use their 2nd pair of appendages for sensing & mating Ex: scorpions seize their prey Purpose of exoskeleton Gives protection Supports internal tissue-gives muscles place to attach Some covers entire body-some animals held together by hinges Made of Chitin Disadvantages of Exoskeleton Relatively heavy structure (Jump & Fly) Cannot grow so they shed periodicallymolting Most molt 4-7 times during their life Most vulnerable to predators Steps Associated with Molting 1. 2. 3. A new one develops beneath the old one The muscles contract in the rear part of the body, forcing blood forward causing this part of the body to swell & split The animal wiggles out Spider Molting http://www.youtube.com/watch?v=zXhdr0TpOwY Body segments of Arthropods Segments have fused into 1 – 3 body sections 1. Head 2. Thorax 3. Abdomen Body segments of Arthropods Other groups have 2 body segments 1. Fused head & thorax called a cephalothorax 2. abdomen Movement Generally quick, & active Can crawl, run, climb, dig, swim & fly Flies beat their wings 1000 times/sec 3 types of Gas Exchange (Air) 1. Gills aquatic arthropods (lobster, crayfish, crab…) exchange gas through gills 3 types of Gas Exchange (Air) 2. Tracheal Tubes Most insects have tracheal tubesbranching network of hollow air passages 3 types of Gas Exchange (Air) 3. Book lungs Most spiders have book lungs – air filled chambers that contain leaf-like plates that look like pages of a book Acute Senses Movement, sound & chemicals are detected with an antennae Antennae also aid in communication Antenna Ants work together because they communicate with a pheromone-which is a chemical odor signal given off by the animal and detected with the antenna A Bugs Life…Wonderful Example http://www.youtube.com/watch?v=jrW_TTxP1ow Vision is important Most arthropods have 1 pair of large compound eyes (visual structures with many lens) Or 3-8 simple eyes (visual structure with 1 lens) Total images make up thousands of parts (dots like a t.v. screen) Nervous System Well-developed that can process information coming in from the sense organ Most excrete waste through Malpighian Tubes Other complex body systems Mouth parts include a variety of jaws called mandibles adapted for holding, chewing, sucking or biting different foods Other information 1. Have separate male & female species 2. Reproduce sexually -fertilization occurs internally in land species -externally in aquatic species 3. Blood is pumped by 1 or more hearts to an open circulatory system 4. Have complete circulatory system, & digestive system Beneficial to Humans 1. 2. 3. Pollinate many flowering plants & crop plants Provide food, honey, shellac, wax & silk Provide alternative chemical control of insects 4. Research has advanced in the fields of genetics, evolution, and biochemistry -Crab shells make artificial skin, surgical sutures & antifungal medicines Problems for Humans 1. 2. 3. Insects eat important crops (bole weevil) Spread plant and animal disease (malaria & yellow fever) Costly for us… Crustaceans Crustaceans: Characteristics: Mostly are aquatic Have mandibles for crushing food 2 pairs of compound eyes which are on moveable stalks 5 pairs of walking legs used to seize prey & clean appendages The first pair of walking legs are often modified into strong claws for defense. Members of Crustaceans Shrimp Crab Barnacles A Few Land Crustacean Pill Bug & Sow Bug, two of the few land crustaceans, must live where there is moisture, which aids in gas exchange Sow Bug Pill Bug Horseshoe Crab Horseshoe crabs are considered to be living fossils & have remained relatively unchanged since the Triassic Period They forage on sandy or muddy ocean bottoms for algae, annelids, and mollusks Insects: class Insecta Insects have three body segments and six legs There are more species of insects than all other classes of animals combined. Only group of animal that has never lost an individual to extinction Centipedes Centipedes are carnivorous and eat soil arthropods, snails, slugs, and worms The bites of some centipedes are painful to humans. Millipedes A millipede eats mostly plants and dead material on damp forest floors. Millipedes do not bite, but they can spray foulsmelling fluids from their defensive stink glands. Leaf Cutter Ants http://www.youtube.com/watch?v=RH3KYBMpxOU Other Members… Lice, Grasshoppers, flies, butterflies, bees & beetles…. Insect Reproduction Most insects lay a large number of eggs, which increase the chances that some offspring will survive long enough to reproduce. The insect embryo develops and the eggs hatch Metamorphosis: change in body shape and form • This series of changes, controlled by chemical-substances in the animal • 2 types of metamorphosis 1. Complete Metamorphosis 2. Incomplete Metamorphosis Complete Metamorphosis Complete metamorphosis consist of four stages on their way to adulthood: Egg Larva Pupa Adult. Incomplete Metamorphosis Incomplete metamorphosis consist of three stages on their way to adulthood Egg Nymph Adult Arachnids Spiders, Scorpions, Mites & Ticks Arachnids 30,000 species of spiders – only 12 native to North America Cannot chew fooduse digestive enzyme to liquefy food Crab Spider Ticks & Mites Differ from spiders because they only have one body segment scorpions Scorpions are easily recognized by their body segments & enlarged pinchers They have a long tail with a venomous stinger at the tip. Arachnids known for webs Silk is made from silk glands & is spun into thread by spinnerets located at the rear of the spider Link for spider webs http://www.i-is.com/users/robin/spiderweb.html Spider spinning an insect http://www.youtube.com/watch?v=_-A8Oe43tjg&NR=1 Venomous Spiders… Black Widow web used in WWI for cross-hairs in riffles Brown Recluse Spiders 1st pair of appendages called chelicera (located near mouth, modified pinchers/fangs) used to hold food 2nd pair called pedipalas handle food & sensing Banana Spider