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Objectives: 1) Describe key features of arthropods. 2) Identify the major

characteristics of arachnids and list example. 3) Explain how an insect differs

from an arachnid. 4) Compare complete metamorphosis with incomplete

metamorphosis. 5) What characteristics do all crustaceans share? 6) Describe

the different groups of crustaceans.

ARTHROPOD CHARACTERISTICS#1 Appendages: extensions of the body that have joints such as:

* Legs for walking* Antenae for sensing* Mouthparts

#2 Very Old: fossils of trilobites dated at 600 million years old.#3 Largest Phylum: 900,00 species

#4 3 Subphyla:Uniramia � JawsChelicerata � Fangs and PincersCrustacea � Fangs and Pincers

#5 Segmentation:HeadThorax Abdomen

*** sometimes the head and thorax are fused to form a cephalothorax***

#6 Compound Eye: made up of individual visual units. Some arthropods also have simple eyes that

are used to detect light and dark.#7 Exoskeleton: Outer shell-like structure covering

the arthropod body. It is made up of chitin.Increase in age = Increase in thickness of the

exoskeleton

#8 Molting: Arthropods shed their old exoskelotonwhen the arthropod reaches a certain size. The new

exoskelteton form under the old one.#9 Respiration: Air enters through spiracles (pores on the side of the body) to the trachea( tube that

delivers O2 to the muscles cells.

Arachnids

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Subphylum ChelicerataClass Arachnia

Characteristics#1 Fangs or Pinchers: called chelicerae#2 Cephalothorax: Head and thorax are fused#3 Pedipalp: 2nd pair of appendages are used tocatch prey.#4 Four pairs of walking legs

Types of Arachnids1) Spiders:

Fangs: Toxin followed by digestive enzymes are injected into the prey. The meal is then sucked.Silk: Most secrete silk from modified appendages called spinnerets

2) Scorpions:1.Stinger tipped abdomen2.Pedipalps are grasping pincers

3) Mites (including ticks): Largest group of arachnidsHead, thorax, and abdomen are fused.

Class InsectaCharacteristicsFact: 50% of all named animals are insects#1 Mandibles: chewing mouthparts (primitive jaws)#2 Body Plan:

Head: contains mouthparts, compound eyes and antenna.Thorax: Legs and wings are attached to the thorax.Abdomen:

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#3 Metamorphosis: 1)Complete Metamorphosis: worm-like larva�Pupa in a chrysalis (capsule)� adult Example: Butterfly

Incomplete Metamorhosis: Egg � smaller wingless adult (Nymph)� after several molts� Adult

Example: Grasshopper

#4 Wings: Most insects have 1 to 2 pairs of wings.#5 Some insects have the ability to form organized societies where different members serve different functions.Example: Ants, Bees, Wasps, and Termites

Subphylum Crustacea#1 Most live in marine habitats, but some live in freshwater and a few even live on land#2 Range in Size: Microscopic water fleas to macroscopic crabs and lobsters.All have a larval from called a nauplius which goes through a series of molts before becoming an adult.

#3 All have mandibles

Groups of Crustaceans#1 Isopods: Pill bugs and Sow bugs

#2 Copepods: Fairy shrimp and water fleas

#3 Decapods: Crayfish, lobsters, and crabs