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The Arthropods: Part 2 Ch. 15 Notes Phylum Arthropoda Review 5 Subphyla: 1. Trilobitomorpha – extinct – trilobites – – Marine Cambrian-Carboniferous time period 2. Chelicerata – spiders, mites, ticks, horseshoe crabs, sea spiders, scorpions 3. Crustacea – ‘hard shelled’ – crayfish, shrimp, lobster, crabs, water fleas, barnacles 4. Myriapoda – millipedes & centipedes 5. Hexapoda – ‘six legs’ – insects & their relatives Subphylum Myriapoda • Class Diplopoda – two-fold foot – Millipedes – 11-100 trunk segments – Two pairs of appendages on each trunk segment – Actually the fusion of two segments • 2 ostia – opening @ end of oviduct • 2 ganglia • 2 tracheal trunks – part of circulatory system – transports O2 – Glands produce Hydrogen Cyanide to repel other animals – Round bodies in cross section Subphylum Myriapoda • Class Chilopoda – lip foot – Centipedes – Nocturnal – Flattened bodies in cross section – Poison claws – Only 1 pair of appendages per segment – Add legs and segments with each molt Subphylum: Hexopoda • Includes Insects & their relatives • Body divided into 3 Tagmata: – Head, thorax, abdomen • 5 pairs of head appendages • 3 pairs of legs on the thorax (6 legs) Class Insecta Habitat: • terrestrial, aquatic, & aerial – Insects are the most successful land animals Class Insecta Locomotion • Flight is the most important form of locomotion – Insects were 1st animals to fly – Must be able to thermoregulate • Maintain body temperatures different from environment • Walk/Run • Jump • Swim Class Insecta Thermoregulation • Ectotherms – Most insects – Rely on sun or warm surface • Heterotherms – Rely on metabolic heat – Shivering Thermogenesis • Generate heat by rapid contraction of flight muscles Class Insecta Digestive Tract • Long & Straight • 3 Regions – Foregut • • • • Musculary pharynx/oral cavity Used for sucking fluids Crop (storage) Gizzard (regulates movement to midgut; grinds food) – Midgut • Surface for digestion & absorption – Hindgut • The Intestine • Reabsorption of Water Class Insecta Excretory System • Nitrogenous wastes converted to uric acid – conserves water – energetically expensive • Malpighian tubules transport uric acid to the digestive tract Class Insecta Respiration – a Simple System • Have trachea- chitin lined tubes – Open to outside through spiracles – Oxygen diffuses from trachea to body tissues • Aquatic insects – Spiracles are nonfunctional – Gasses diffuse across body wall • Blood is not important for gas exchange in insects Class Insecta Do insects have blood? Circulatory System • Open Circulatory System • Less developed blood vessels • Blood distributes nutrients, hormones, & wastes Class Insecta Nervous Communication • Pheromones – Chemicals released by one individual that affects the behavior of another – Chemoreceptors – pores through which chemicals diffuse • • • • Feeding Selection of egg laying sites Mate location Social organization Class Insecta Nervous Communication Continued… • Hormones regulate – Ecdysis – Metamorphosis • Eclosion – the emergence of an insect from a cocoon, chrysalis, or puparium – Cocoon- Protective case enclosing the pupal stage, made of silk – Chrysalis- Last larval exoskeleton maintained during the pupal stage – Puparium- an outer covering that protects the pupae of some flies Class Insecta Nervous Communication Continued… • Insects are capable of memory • Johnston’s organs – the base of the antennae of most insects – Long setae that vibrate when certain frequencies of sound strike them – Mosquitoes and fruit flies hear using the Johnston's organ Class Insecta Nervous Communication Continued… • Sense organs – Mechanoreceptors – perceive physical displacement of the body or body parts – Setae – distributed over mouthparts, antennae, legs • Touch, air movements, and vibrations move setae – Stretch Receptors – located @ joints & muscles • Monitor position and posture Class Insecta Nervous Communication Continued… Sound • Tympanic organs – Consist of a thin, membrane covering a large air sac – Air sac acts as a resonating chamber – Sensory cells under membrane to detect pressure waves Class Insecta Nervous Communication Continued… Sight • All insects are capable of detecting light • Compound Eyes – – – – – Well developed eyes Not a very good image Good at detecting movement Sometimes can detect polarized light Made up of 1000’s of Ommatidia • Each is a lens w/ a crystaline cone • Cells have a rhabdom light collecting area – Converts light energy into nerve impulses • Ocelli – simple eyes – Hundreds of photo receptors Class Insecta Reproduction • Adaptations for land – Resistant eggs – External genitalia – Behavioral mechanisms that bring males and females together at appropriate times • Pheromones • Visual signals • Auditory signals Class Insecta Relationships • Many insects are social – They live in colonies – Each kind of individual in an insect colony is called a caste • Many are beneficial to humans • Few are parasites or transmit diseases to humans or plants