Biol 11 Lesson 2 April 7 - Arthropoda Station Info Sheets
TrilobiteSubphylum Trilobita (trilobites)Example members: trilobites (now extinct)Key features:-body composed of many segments-each segment had 2 appendages (each appendagewas divided into 2 branches – a walking leg and afeather-like gill)Subphylum Crustacea (crustaceans)Example members: crabs, shrimp, lobster, water fleas, barnacles, pill bugs, crayfishKey features:-35 000+ members-members are primarily aquatic-members vary in form and size-3 body segments (head, thorax, and abdomen) sometimes headand thorax are fused into a cephalothorax-hard exoskeleton (aka carapace) reinforced with calcium carbonate(CaCO3) (aka limestone)-2 pairs of antennae (“feelers”) and mandibles-gas exchange with gills-each walking leg is attached to a gill (like in trilobites)-swimmerets – flipper-like appendages for swimmingCrustaceans have appendages that vary greatly. For example, crayfish have claws, walking legs,swimmerets and uropods, as well as modified mouth parts.
Subphylum Chelicerata (chelicerates) TickExample members: spiders, scorpions, ticks, mites, horseshoe crabs2 classes 1) Class Arachnida (arachnids such as spiders, scorpions, ticks, mites) 2) Class Merostomata (horseshoe crabs). A very ancient class (“living fossils”). Not really crabs, of course.Key features:-body divided into 2 segments (a cephalothorax (head fused with a thorax) and an abdomen)-4 pairs of walking legs on cephalothorax-most are carnivores-have air tubes and book lungs-sensory bristles covering body instead of antennaeUnique to chelicerates are 2 pairs of appendages attached near mouth: 1) Chelicerae – spiders use these appendages to bite and paralyze prey Spiders inject enzymes that liquefy the prey and they suck the “juice” out!! 2) Pedipalps – 1 pair of appendages usually used for handling prey In scorpions, modified into huge clawsAll spiders can produce silk (a tough protein that is 5x stronger than steel!). Some spiders spin websusing spinnerets.Ticks and mites are usually parasites. Ticks can carry diseases,such as Lyme disease, which can cause joint inflammation, andheart rhythm and neurological problems.
Subphylum Uniramia (uniramians)Example members: millipedes, centipedes, insects‘Uni’ – one, ‘ramus’ = branchAll uniramians have 1 pair of antennae and appendages that do not branch.There are (at least) 3x more species of uniramians than all other groups of animals! Centipede3 classes 1) Class Chilopoda (centipedes) -Predatory carnivorous -Head has 1 pair of antennae and a chewing mouth -1st body segment has a pair of poisonous claws -2 groups of simple eyes -1 pair of legs per segment 2) Class Diplopoda (millipedes) -Detritus feeders scavengers -Head has 1 pair of antennae and a chewing mouth Millipede -2 pairs of legs per body segment 3) Class Insecta (insects, such as bees, moths, grasshoppers, etc.) -900 000+ species -3 part segmented body: head, thorax, abdomen -3 pairs of legs attached to thorax -1 pair of antennae and 1 pair of compound eyes -Often have 2 pairs of wings on the thorax -Tracheal tubes for respiration Anatomy of a wasp
Grasshopper mouthpartsInsect AdaptationsFeeding :-3 pairs of appendages used as mouthparts including mandibles (cutting jaws)-may secrete digestive enzymes or other chemicals ex. mosquitoes – anticoagulants prevent blood clotting bees – change nectar to honeyMovement :-Legs have spines and hooks for defense-Legs used for jumping, holding prey (ex. praying mantis)-Unassisted flight with wings (variety of speeds and maneuverability)Insect societies:Society: collections of individuals of the same speciesthat live togetherIndividuals depend on one another (ex. ants, bees,termites)Division of labour: members of different castes (typesof individuals) have a body that is specialized for itsfunction (ex. reproductive females, reproductive males,workers) Termite castesCommunication:-Use sound, visual, chemical signals for mating (ex. cricket chirp, firefly light)Pheromones: convey info of food through a “waggle dance” (see p. 627) Waggle dance
Compound eyesIntriguing Structures in Class InsectaCompound EyeMany arthropods have compound eyes.Compound eyes are made up of repeating units, theommatidia, each of which functions as a separate visualreceptor.‘Microscope A’ shows a slide of a compound eye. Spiracles Insects and some more advanced spiders have spiracles on their exoskeletons to allow air to enter the trachea. In insects, the tracheal tubes deliver oxygen directly into the animals tissues. The spiracles can be opened and closed in an efficient manner to reduce water loss. ‘Microscope B’ shows a slide of an insect spiracle. Honeybee mouthpartsMouthpartsMany insects have mouthparts adapted forfeeding. Honeybees have a number ofadaptations for gathering, processing, andstoring food.In honeybees, the mandibles are very small andsuitable for moulding wax. The labium is curveddownwards and inwards forming a tube usedfor sucking up nectar.‘Microscope C’ shows a slide of honeybeemouthparts.