G Kingdom Animalia Part 1

32.1 Phylum Arthopoda *vertebrates: spine *invertebrates: no spine Characteristics • Jointed appendages [extensions of the body; include legs and antennae] • Segmented body; a pair of appendages are attached to each segment • Exoskeleton: hard external covering for protection and support o Composed primarily of protein and chitin ( a tough carbohydrate) o Three layers: [all three layers are secreted by an epidermis beneath them] -waxy outer layer repels water and prevents desiccation in terrestrial species -middle layer is primary protection (strengthened by materials such as calcium) -inner layer is flexible at joints and allows the animals to move freely • Ventral nervous system • Open circulatory system • Digestive system • Specialized sensory receptors Movement and Growth • Muscles occur in bundles that attach to the inside of the exoskeleton on either side of the joints • By alternately contracting and relaxing the muscles, the arthropod in essence operates a system of levers that move the body parts and appendages • Molting [also called ecdysis] o Arthropods molt many times during their lifetime o Exoskeleton cannot enlarge as the body does and therefore must be shed periodically and a new one must be formed o the tissues of the arthropod grow until they put a great deal of pressure on the exoskeleton walls, a hormone is then produced that induces molting o When arthropod begins molting, cells of epidermis secrete enzymes to digest flexible inner layer of exoskeleton; simultaneously epidermis begins synthesizing new exoskeleton, using mush of the digested material o During this process outer layer of old exoskeleton loosens and breaks along specific lines and is then shed o The new exoskeleton is flexible at first and stretches to fit o Arthropods usually go into hiding until their new exoskeleton has hardened because during molting the arthropod is vulnerable to predators due to lack of a hard shell; terrestrial arthropods are also susceptible to desiccation during molting

Evolution and Classification • Inferred that arthropods evolved from a common ancestor because of exoskeleton and jointed appendages; but suggested there are actually four separate lines of arthropod evolution; now classified into four subphyla: o Trilobita – includes extinct organisms called trilobites o Crustacea – includes shrimp, lobsters, crabs, barnacles, cladocerans, ostracods, crayfish, water fleas, and copepods o Chelicerata – includes spiders, scorpions, ticks, mites, sea spiders, and horseshoe crabs o Myriapoda (Uniramia) – only group that seems to have evolved on land and includes centipedes, millipedes, and all of the insects • Members of the subphyla are primarily distinguished by differences in their embryological development and differences in the morphology of structures such as appendages and mouthparts o Chelicerata – distinguished by absence of antennae and the presence of pincerlike mouthparts called chelicerae o Crustaceans – distinguished by presence of the branched antennae and chewing mouthparts called mandibles o Myriapoda (Uniramia) – also distinguished by having antennae and mandibles but their appendages are unbranched [Uniramia means “one branch”] • Despite the differences, the three subphyla of living arthropods have evolved similarly o Ancestral arthropods had one pair of appendages per segment, but most living species have fewer appendages than this o The evolution of these groups shows a general tendency toward less segmentation of the body: ancestral arthropods had many segments while most modern adults have some segments fused together into larger structures with specialized functions

32.2 Subphylum Crustacea • Exoskeletons • Include crayfish, lobsters, pill bugs, sow bugs, water fleas, and barnacles • Mostly aquatic Characteristics • 2 pairs of antennae • Mandibles • Pair of appendages for each segment • At least some are branched • Large crustaceans (crayfish and lobsters) use gills to respire (breathe) • Exoskeleton made of CaCO3 (calcium carbonate); therefore very hard • Embryo is free-swimming larvae (“nauplius”) Diversity • Most are small o Copepods  no bigger than a comma  inhabit surface waters of oceans, lakes, and streams o Barnacles  sessile (immobile)  attach themselves to rocks, docks, pilings, boats, whales, turtles  filter plankton from the water with 12 appendages called cirri o Sow bugs and pill bugs  are terrestrial  7 identical pairs of legs  called isopods (means “same feet”)  live in damp areas where their gills can stay moist

Crayfish • Order Decapoda (crayfish, lobsters, crabs, shrimp are decapods) o decapods – 10 feet External Structure • body divided into 2 sections o cephalothorax (13 segments) 1. head (5 segments) • antennule: antennalike appendage with receptors for touch, taste, and equilibrium • antenna/antennae: an appendage specialized for touch and taste • cheliped: a claw used to capture food and to provide defence • mandible: moveable mouthpart that usually functions in chewing • maxilla/maxillae: structure behind the mandibles that helps hold and cut food • maxilliped: a specialized appendage used to hold food 2. thorax (8 segments) • walking legs 3. carapace: covers the cephalothorax (1 unit) o abdomen (7 segments) • telson  7th segment  forms a flat triangular section at the tail of the animal  powerful abdominal muscles can jerk this tail and propel the animal rapidly backward • uropods  attached to 6th segment  used for swimming • swimmeret  creates water currents and functions in reproduction Digestive and Excretory Systems • trap food with chelipeds, tear it with the maxillae and maxillipeds, chew it with the mandibles • food passes through esophagus to stomach where chitinous teeth grind it into a fine paste • paste is mixed with enzymes secreted by digestive gland • digestive glands absorb the mixture • undigested particles pass through the intestines and out the anus

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excretory organs, called green glands, remove wastes from the blood and retain salts (which are scarce in fresh water) live in hypotonic environment  H2O constantly enters by osmosis; H2O eliminated by green glands  leaves body through a pore at the base of the antennae

Circulatory and Respiratory Systems • Circulatory o open circulatory system o blood flows from a dorsal sinus through small, one-way valves called ostia into the dorsal heart o heart pumps blood into 7 large vessels that carry it through the body o blood leaves the vessels and fills the body cavity where it bathes the organs and cells o blood collects in a large, ventral sinus o other vessels then carry the blood through the gills, where it gives off CO2 (carbon dioxide) and takes up O2 (oxygen) o it then returns to the dorsal sinus • Respiratory o Gills attached to each walking leg, protected in a chamber under the carapace o As the crayfish walks water moves across the gills o As the second maxillae move during feeding, the 2 gill bailers attached to them “bail” water over the gills Nervous System • Brain with a ventral nerve cord that runs from the brain to the tail • Nerve impulses travel to and from the nerve cord through ganglia • Nerves connect the brain with sense receptors in the antennules, antennae, and eyes • Compound eyes o are set on 2 short, moveable stalks o each eye has ~2000 light-sensitive lenses o Detect motion well though they can only form crude images • Statocysts o used to sense position; cells that contain particles of CaCO3 (calcium carbonate) which move when the crustacean’s position changes; this movement is monitored by the nerves and interpreted by the brain Reproduction and Development • usually mate in fall • male uses 1st and 2nd swimmerets to transfer sperm to the seminal receptacle of the female • sperm remains there until spring when it fertilizes the egg as the female lays them • sticky secretion attaches the eggs to the last 3 pairs of the female’s swimmerets

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eggs hatch after ~6 weeks, having gone through several larval stages young look like tiny adults they molt repeatedly: average of 7 times during the first year, then twice a year for the remaining 2 or 3 years of their lives

32.3 Other Arthropods Subphylum Chelicerata, Class Arachnida • Include spiders, scorpions, mites, sea spiders, horseshoe crabs • Most adapted to kill prey with poison glands, stingers, or fangs • Have body divided into 2: 1. cephalothorax (6 pairs of jointed appendages)  four pairs of walking legs  1 pair of chelicerae: fangs  1 pair pedipalps: aid in chewing (hold food); in some species they’re specialized for other functions 2. abdomen • lack antennae • have 6 pairs of appendages • first pair of appendages: chelicerae – are modified pincers or fangs Structure and Function • Share many characteristics with crustaceans (ex. The nervous, digestive, and circulatory systems of both groups are structurally similar) • Respiratory System o Respire through openings in the cuticle called spiracles o Air passes through spiracles to the book lungs, the tracheae, or both o Book lungs  paired sacs in the abdomen  pagelike components  provide a large surface area for the exchange of gases o Tracheae  carry air directly to the tissues • Excretory System o Main excretory organs: Malpighan tubules  hollow projections of the digestive tract  collect bodily fluids  remove wastes  carry wastes to the intestine

o most of the water is reabsorbed and the solid wastes leave the body o some have coxal glands  organs that remove wastes and discharge them through an opening at the base of the leg

Scorpions • most live in tropical or semitropical areas and are nocturnal; others are in dry temperate or desert regions; conserve water by excreting concentrated waste • differ from spiders in 2 ways: 1. have greatly enlarged pedipalps which they hold in a forward position (use pedipalps to hold food) 2. have a large stinger on the last segment of the abdomen (poison) • seize their prey with pincerlike pedipalps; fang injects paralyzing venom; chelicerae tear at prey; then ingested and digested Spiders • body very narrow between cephalothorax and abdomen • feed mainly on insects; some prey on fish, frogs, or birds; • some chase prey, some catch prey in ‘trapdoors’ in the ground, some snare prey in webs • some have paralyzing venom • enzymes are secreted into the prey to digest it • have 8 simple eyes (with simple lenses) at anterior end of cephalothorax • spinnerets o posterior tip of abdomen contains 3 pairs of spinnerets o each made up of hundreds of microscopic tubes connecting to silk glands o fluid from silk glands passes through the tubes and hardens into a thread that can be spun into webs o silk also used to build nests and cocoons; the young of some species use a long thread to catch the wind and move to new habitats o Spider silk is composed of complex protein molecules • reproduction o male spider gathers sperm in special sacs in the tips of the pedipalps; places the sperm in the seminal receptacle of the female o later female lays eggs which are fertilized by the stored sperm as they pass through the genital spore o female then seals eggs in case of silk o young spiders go through first molt inside the case

o the female spider will sometimes eat the male after mating 1. Black Widow – has venom; bright red/orange mark on abdomen 2. Brown Recluse – has violin mark on its abdomen

Mites and Ticks • very small • unlike other arachnids, have fused cephalothorax and abdomen • most abundant and most specialized arachnids • some are pests; others transmit diseases 

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Spider Mites damage fruit trees when they suck fluid from the leaves

Many parasitic ticks pierce their host’s skin to feed on blood; in this process they can transmit organisms that can cause diseases  

Lyme disease Rocky Mountain Spotted Fever

Subphylum Myriapoda (“many feet”) • OLD NAME: UNIRAMIA • Terrestrial • No waxy cuticle; retain moisture through behavioural adaptations, such as living in damp environments to prevent desiccation Class Diplopoda – Millipedes (“thousand legs”) • 2 pairs of legs on each segment except the last 2 (up to 100 segments • Short antennae • 2 groups of compound eyes • Legs strong and well adapted to burrowing through humus and soil • Short legs; mover slower • When threatened they roll their body into a coil and may also spray a noxious chemical that contains cyanide • In a cross section their bodies are rounded • Live in soil, logs, under objects • Many have strong sense of smell but poor vision • Herbivores adapted for chewing plants and decayed matter in soil Class Chilopoda – Centipedes (“hundred legs”) • Body flattened in cross section • One pair of legs per segment except the first 1 and the last 2 • Legs longer; can move faster • Many coil up for defence • May have anywhere from 15 to 175 pairs of legs • Carnivores: feed on earthworms and on insects (such as cockroaches) • The first body segment has a pair of clawlike appendages that can inject venom into prey • Long antennae • 2 groups of compound eyes

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Eat using mandibles and maxilla