Subphylum Trilobita (trilobites)

Example members: trilobites (now extinct)

Key features: -body composed of many segments-each segment had 2 appendages (each appendage was divided into 2 branches – a walking leg and a feather-like gill)

Subphylum Crustacea (crustaceans)

Example members: crabs, shrimp, lobster, water fleas, barnacles, pill bugs, crayfish

Key features: -35 000+ members-members are primarily aquatic-members vary in form and size-3 body segments (head, thorax, and abdomen) sometimes head and 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 swimming

Crustaceans have appendages that vary greatly. For example, crayfish have claws, walking legs, swimmerets and uropods, as well as modified mouth parts.

Trilobite

Subphylum Chelicerata (chelicerates)

Example members: spiders, scorpions, ticks, mites, horseshoe crabs

2 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 antennae

Unique 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 preyIn scorpions, modified into huge claws

All spiders can produce silk (a tough protein that is 5x stronger than steel!). Some spiders spin webs using spinnerets.

Ticks and mites are usually parasites. Ticks can carry diseases, such as Lyme disease, which can cause joint inflammation, and heart rhythm and neurological problems.

Tick

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!

3 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-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

Centipede

Millipede

Insect Adaptations

Feeding : -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 honey

Movement : -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 species that live togetherIndividuals depend on one another (ex. ants, bees, termites)Division of labour: members of different castes (types of individuals) have a body that is specialized for its function (ex. reproductive females, reproductive males, workers)

Communication: -Use sound, visual, chemical signals for mating (ex. cricket chirp, firefly light)Pheromones: convey info of food through a “waggle dance” (see p. 627)

Grasshopper mouthparts

Termite castes

Waggle dance

Intriguing Structures in Class Insecta

Compound Eye

Many arthropods have compound eyes. Compound eyes are made up of repeating units, the ommatidia, each of which functions as a separate visual receptor.

‘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.

Mouthparts

Many insects have mouthparts adapted for feeding. Honeybees have a number of adaptations for gathering, processing, and storing food.

In honeybees, the mandibles are very small and suitable for moulding wax. The labium is curved downwards and inwards forming a tube used for sucking up nectar.

‘Microscope C’ shows a slide of honeybee mouthparts.

Compound eyes

Honeybee mouthparts