Chapter 28 Arthropods and Echinoderms

Phylum Arthropoda - Arthropods  Largest and most successful phylum  75% of all animals!  Segmented body  Tough exoskeleton  Joint appendages (legs and antennae)  Cephalization  Bilateral Symmetry

 Exoskeleton: an external covering that protects and supports the body –Made from chitin –Varies in size, shape, and roughness.  Firm and leathery (caterpillars)  Tough and hard (crabs and lobsters)  Waxy (land dwelling arthropods)

Feeding  Feeding –Herbivores –Carnivores –Omnivores –Detritivores –filter feeders –Bloodsuckers –parasites. –Mouth parts adapted to type of food eaten  Pincers, fangs, jaws

Terrestrial arthropods: breathe through tracheal tubesTerrestrial arthropods: breathe through tracheal tubes Air enters and leaves tracheal tubes through spiraclesAir enters and leaves tracheal tubes through spiracles small openings located along the side of the body. small openings located along the side of the body. Tracheal tubes Spiracles RESPIRATION

Book lungs organs that have layers of respiratory tissue (stacked like pages of a book.) Spiders, scorpions, horseshoe crabs RESPIRATION CONTINUED…

Circulation and Excretion  Arthropods have a open circulatory system –A well developed heart pumps blood through arteries  Malpighian tubules (terrestrial): saclike organs that extract waste from the blood  Diffusion (aquatic)

Response and Reproduction  Response –Well developed nervous system –Brain serves as central switchboard  Reproduction –Terrestrial arthropods: internal fertilization  Place sperm inside female OR deposit sperm packet –Aquatic arthropods: internal or external

 Movement: Groups of well developed muscles coordinate movement –generating force by pulling on the exoskeleton –Muscles flex (bend) or extend (straighten) the joint. MOVEMENT

Growth and Development  Arthropods will outgrow their exoskeleton and undergo a period called molting.  Molting: the shedding of its entire exoskeleton –New/soft skeleton starting to form –Controlled by the endocrine system

28-2 Groups of Arthropods  Classified by number of body segments and mouth parts  3 major groups 1.Crustaceans 2.Spiders and their relatives 3.Insects and their relatives

1) Crustaceans (sub phylum Crustacea)  Primarily aquatic –Includes crabs, shrimps, lobsters, crayfishes, and barnacles. –2 pairs of antennae, two or three body sections, and chewing mouthparts called mandibles. Cephalothorax Abdomen Mandible Antennae Antennules

Body Plan of Crustaceans  Cephalothorax –Fusion of head with the thorax  Mandible : –Mouthpart adapted for biting and grinding food swimmerets Cheliped Cheliped: first pair of legs that have large claws modified to catch, pick up, crush, and cut food. Swimmerets: flipper- like appendages used for swimming

2) Chelicerates (sub phylum Chelicerata)  Horseshoe crabs, spiders, ticks, and scorpions –No antennae –Have mouthparts called chelicerae (stab and paralyze) & pedipalps (grab prey) –2 body sections –4 pairs of walking legs  Divided into 2 main classes:  Merostomata (horseshoe crabs)  Arachnida (spiders, mites, ticks, and scorpions)

Horseshoe crabs Horseshoe Crabs  Appeared more than 500 million years ago  Have chelicerae, five pairs of walking legs, and a long spike-like tail (telson) that is used for movement.

Spiders  Food and Digestion –Spin webs of a strong, flexible protein called silk –No jaws for chewing  must liquefy food using enzymes  Use fanglike chelicerae to inject paralyzing venom

What does the spider use silk for? Silk Silk glands Spinnerets

Mites, Ticks, and Scorpions  Mites and ticks are small arachnids that are often parasitic  Ticks can transmit bacteria that cause serious diseases –chelicerae and pedipalps are specialized for digging into a host’s tissues and sucking out blood  Scorpions inhabit warm areas around the world. –Chew their prey

3) Uniramians (sub phylum Uniramia)  Centipedes millipedes, and insects  Characteristics of Uniramians –Have jaws, –One pair of antennae –Un-branched appendages –Live under rocks  Centipedes: one pair of legs on each segment; carnivorous  Millipedes: two pairs of legs on each segment; eat dead & decaying plant matter

28-3 Class Insecta (Insects)  Characteristics of Class Insecta –most species of any other animals –Body divided into 3 segments  Head, thorax, and abdomen

Characteristics continued…  Segmented body  Exoskeleton  Jointed appendages  A typical insect also has:  a pair of antennae  a pair of compound eyes  two pairs of wings on the thorax  tracheal tubes that are used for respiration

Response  Compound Eye: made up of many lenses –Detect minute changes in color and movement  Chemical receptors for taste and smell  Sensory hairs: detect movement in surrounding air or water  Well developed ears

Feeding and Specialized Mouth Parts  3 pairs of appendages that are used as mouthparts, including a pair of mandibles Mandibles used to saw and grind food Ant

Specialized mouth parts continued… Spongelike mouthpart used to lap up food Fly

Specialized Mouth Parts Tubelike mouthpart used to suck nectar Moth

Movement and Flight  3 pairs of legs used for walking, jumping, capturing and holding prey. –Legs have spines and hooks that are used for grasping and defense.  Flying insects typically have two pairs of wings made of chitin

Metamorphosis  Process of changing shape and form –Insects undergo either incomplete metamorphosis or complete metamorphosis  Incomplete Metamorphosis –Look very much like adult form –Immature forms are called nymphs  lack functional sexual organs and wings

Complete Metamorphosis  Animals hatch into larvae that look and act nothing like their parents  Feed and grow rapidly and molt a few times  Undergo a final molt and change into a pupa –stage in which an insect changes from larva to adult.

INSECTS AND HUMANS  Contribute to richness of life  Pollinate crops  Produce silk, wax, honey  Considered a food delicacy in certain countries

Insect societies  Ants, bees, termites form insect societies –Same species that work together for the benefit of the whole group  A caste is within these societies –Individuals specialized for certain roles –Ex: queens (lay eggs), reproductive males, workers

Communication in societies  Each society has its own “language”  Worker ants leave a pheromone trail to guide her nest to food locations  Honey bees can communicate about quality of food and direction –2 dances: round and waggle dance (close and far away)

Communication Continued…  Round dance –Circle one way and then another. –The more time they change direction the better quality of food  Waggle dance –Runs forward –Circles one way –Runs straight again –Circles the other way