2. Phylum Arthropoda (Insects, spiders & crustaceans)

3. Appearance Symmetry: bilateral Segmentation
Jointed appendages: modified for walking, feeding, sensory, copulation & defense
Hard exoskeleton made up of protein and a flexible substance called chitin.
The chitin is coated with a waxy layer making the exoskeleton water proof.

4. The exoskeleton Advantages Disadvantages
Protects arthropods like a coat of armour
Provides support for muscles and internal organs
Disadvantages
A hard external exoskeleton that is non-living and therefore cannot grow with the animal.
Heavy and restricts the size of the arthropod

5. Exoskeleton
Exoskeleton is secreted by the underlying epidermis and shed at intervals
This process is called moulting and allows the animal to continue to grow.
A newly moulting Cicada (right)

6. Circulation Open circulatory system with a well developed heart.
Blood is pumped through the body sinuses and eventually collects in a large cavity near the heart, called a hemoceol, where it re enters the heart.
Hemoceol
Heart
Artery

7. Movement Well developed muscles coordinated by the nervous system
Move by contracting muscles which are attached to the exoskeleton

8. Feeding Herbivors, carnivores, filter feeders, detritus feeders
Appendages are adapted to specialized mouthparts used for feeding
siphon

9. Respiration Gills (crustaceans) Book gills/book lungs (spiders)
Feathery gills
Book gills/book lungs (spiders)
Several sheets of tissue layered like the pages in a book
This increase surface area to volume ratio
Tracheal tubes (insects)
Long tubes that reach deep into tissue where
O2 diffusion takes place
Connects to the air via spiracles

10. Nervous System Very well developed nervous system
Can smell, taste and see – compound eyes can detect motion extremely well

11. Nervous System
Brain = a pair of ganglia that acts like a central switch board for incoming information
From the brain, a nerve cord runs along the ventral part of the body.
Along the nerve cord there are more ganglia which serve as a command center for the specific segments

12. Excretion Solid waste exits via the anus Nitrogenous wastes
In Aquatic arthropods – excreted through the green gland near the base of the antennae
In spiders – Malphighian tubules –removes nitrogenous wastes from blood and adds it to undigested food

13. Reproduction Dioecious
Fertilization usually takes place inside the body of the female
In spiders and some crustaceans, males deposit a sperm packet
Insects and most crustacean males have a special reproductive organ to deposit sperm inside the female

14. Complete Metamorphosis
Egg hatches into a larva that looks nothing like the adult
As the larva grows it moults
Larva sheds it skin and becomes a pupa – the insects body is rearranged
This occurs in a protective cocoon.
Adult insect emerges from cocoon as complete adult

15. Incomplete Metamorphosis
Egg hatches into a miniature adult but with no functioning sex organs
At this stage the insect is called a nymph
As is grows it moults as it gets bigger
At this stage the insect is called a juvenile
Along the way the insects acquires adult characteristics

16. Ecological and Economical Importance
Plants depend on them for pollination
Many symbiotic relationships
Ex. Fish/cleaner shrimp
Aid in agriculture
Silk production
Pollination
Eat harmful species (ladybugs eat aphids)
Can also damage crops (locust) and transmit diseases (mosquitoes)

17. Three Subphylums Chelicerae Crustacea Uniramia
Spiders, horseshoe crabs and scorpions
Crustacea
Crayfish, fleas, crabs, barnacles
Uniramia
Insects, centipedes, millipedes
Using your textbook, research the differences among these subphyla.

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