Ch. 15 Notes The Arthropods: Part 2

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 – trunk segments – Two pairs of appendages on each trunk segment – Actually the fusion of two segments 2 ostia – end of oviduct 2 ganglia 2 tracheal trunks – part of circulatory system – transports O 2 – 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 1 st 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 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 – 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