1. PHYLUM ARTHROPODA Largest phylum of the animal kingdom
Arthropod species account for ~ 75% of all animal species
Evolved ~ 600 mya

2. Taxonomy

3. General Characteristics
All arthropods share three general characteristics:
Jointed appendages
such as jointed legs and antennae
arthropod actually means “jointed foot”

4. General Characteristics
Exoskeleton
external skeleton that helps protect and support
has three layers
outer = wax to repel water and prevent from desiccating (drying out)
middle = protein + chitin + calcium carbonate for protection (like armour plating)
inner = protein + chitin, flexible protection (like chain mail)
limits maximum size of arthropods as exoskeletons become very heavy as the animal gets bigger
does not grow, must be molted and then re-grown

5. General Characteristics
Segmented Body
Each segment generally contains at least 1 pair of appendages
Arthropod success is explained, in part, due to the diversity of their appendages
Legs
Antennae
Pincers and claws
Stingers
Wings
Jaws
Paddles
Gills
Spinnerets (for spinning webs)

6. General Characteristics
Segmented Body
Sometimes different segments are fused together to form tagmata which may be specialized for
Feeding
Locomotion
Reproduction
Body structure often includes (especially all insects):
Head: arthropods are highly cephalized
Thorax
Abdomen

7. Other Common Characteristics
Open Circulatory System
Have a hemocoel = cavity containing internal organs
Hemolymph (essentially blood) is not contained in vessels, simply bathes the organs within the hemocoel
Well Developed Nervous System
ladder-like
2 ventral nerve cords (rails) linked by cross nerves (rungs)
Well Developed Respiratory System
Terrestrial arthropods have lungs or air sacs
Aquatic arthropods have gills

8. Taxonomy

9. Taxonomy –Subphylum Trilobita
An extinct subphylum characterized by:
very long antennae
many segments
hard exoskeleton

10. Taxonomy –Subphylum Uniramia
An extant (currently living) subphylum characterized by:
one-branched (or non-branched) appendages
have antennae and mandibles (jaws)
appear to have evolved on land
Three Main Classes
Class Chilopoda
Centipedes with flattened body and 1 pair of legs per segment
Class Diplopoda
Millipedes with rounded body and 2 pairs of legs per segment
Class Insecta
Flies, grasshoppers, bees, wasps, ants, buttlerflies, moths and beetles that have madibles, antennae, unbranches appendages, 6 legs, and often one or two pairs of wings

11. Taxonomy –Subphylum Chelicerata
An extant (currently living) subphylum characterized by:
lack of antennae
Presence of pincer-like mouthparts called chelicerae
Three Main Classes
Class Xiphosura
Horseshoe crabs
Class Arachnida
Spiders, scorpions, mites and ticks that have a cephalothorax and abdomen and 8 legs

12. Taxonomy –Subphylum Crustacea
An extant (currently living) subphylum characterized by:
two pairs of “feelers” on head
have branched appendages
mostly aquatic including copepods, water fleas, barnacles, crab, shrimp, crayfish, lobster
terrestrial exception – pill bugs/rolly-pollies

13. Insects-Chapter 39 http://www.youtube.com/watch?v=Na5ms4UxU0s

14. Classification of Insects
Phylum Arthropoda
Subphylum Uniramia
Class Insecta
Entomology = the study of insects
Entomologist = scientists that study insects

15. Characteristics of Insects
Segmented body
divided into three tagmata:
Head
Thorax
Abdomen
Jointed appendages
Exoskeleton

16. Characteristics of Insects
Most insects are small
They have jaws = mandibles
One pair of antennae on head
Thorax has three pairs of jointed legs
Many species one or two pairs of wings
Abdomen composed of 9-11 segments

17. INSECT DOMINATION!
= 80% of all organisms that scientists have classified and named
inhabit almost every imaginable niche and ecosystem on the planet including the Arctic

18. WHY INSECT DOMINATION? exoskeleton diverse jointed appendages small
rapid and numerous reproduction
incomplete and complete metamorphosis

19. Insects and People The Negative Effects crop damage
spread disease via bites
some fleas carry plague
damage buildings (Termites)
allergies to bites

20. Insects and People The Positive Effects
Insects play vital role in almost all terrestrial and freshwater environments
Serve as food for many other animals
Cross pollinate plants
Estimated that insects pollinate 40% of worlds flowering plants
Provide us with:
honey
wax
silk