1. Phylum Arthropoda “ joint” “foot” 80% of all animals are arthropods…..
76% of those are insects…..

2. Major Classes of Arthropods
Above:, Class Diplopoda: includes the millipedes
Above left: Class Chilipoda: includes the centipedes
Lower Right: Class Insecta: includes all 6 legged insects

3. Above Class Malacostraca: includes the lobsters, crab and shrimp
Above Class Arachnida: includes the spiders, mites and scorpions

4. Features Jointed appendages segmented
Coelomate and bilaterally symmetrical
Exoskeleton of made of chitin secreted by the epidermis
Open circulatory system
Respiration by body surface, gills, trachea, or book lungs
Sensory organs are well-developed: compound eyes, tympanum (drum-like ear) antenna (touch, smell, chemical reception)
Developed nervous system with dorsal brain connected by a ring and double ventral nerve cords
Dioecious: fertilization is usually internal

5. Growth and Development
molt- shedding previous exoskeleton for a new one in order to grow
metamorphosis- changes that the arthropods undergo as they develop from a larva to an adult
grasshoppers undergo incomplete metamorphosis, when they hatch they resemble the adult form
Butterflies undergo complete metamorphosis in which the hatched egg looks completely different then the adult butterfly

6. Obtaining Nutrients
carnivores- feed on dead animals and prey on exoskeleton animals ( ex: spiders )
herbivores- some fed on particular plants only others feed on various types of greenery
parasites- blood or body fluids of host(ticks)
filter feeders- marine arthropods
detritus feeders- decayed plants and animals

7. Feeding Digestive tract with two openings (one-way digestion)
Mouthparts of individual species are highly specialized for a particular food type
e.g. Australian Bulldog Ant (or bullant) – it’s diet includes small insects, seeds, fruit, and fungi

8. Respiration Specialized organs for gas exchange
Aquatic species have gills
Terrestrial species have tracheal systems

9. Respiration in Aquatic Species
Aquatic species have gills
formed from the appendages that form mouth and legs, water continuously travels through
Some aquatic species (horseshoe crab) have book gills
Leaf-like layered tissue that increases the surface area of gas exchange and have blood vessels

10. Respiration in Terrestrial Species
Terrestrial species have tracheal system
openings called spiracles lead to a network of tubes called tracheal tubes which run throughout the body
the movement of the animal causes the rhythmic pumping that allows air to enter through the spiracles and into the tracheal tubes

11. Movement
Well developed groups of muscles are controlled by the nervous system.
Muscle cells are attached to the exoskeleton in order to generate force.

12. Reproduction Sexual reproduction and all members are separate sexed
Terrestrial species have internal fertilization.
In some species, males have organs which place the sperm inside the females while others deposit a sperm packet that is picked up by the female.
Aquatic species can have either internal or external fertilization where eggs and sperm are broadcast into the surrounding waters.

13. Class Chilopoda The Centipedes About 30-35pairs of legs
Very annelid-like with repeating segments
Setae are modified to crude appendages - only specialized in the mouthparts
Centipedes are carnivores with venomous mouthparts and feed on earthworms, toads, snakes, and mice

14. Class Diplopoda The Millipedes
Very annelid like but have an exoskeleton
No antennae
Millipedes are herbivores and may defend themselves by secreting unpleasant or toxic chemicals

15. Subphylum Crustacea E.g. crabs, shrimps, lobsters, & crayfishes,
2 pairs of antennae (typically) & chewing mouthparts called mandibles
2 or 3 body sections: head, thorax, and abdomen (often the head and thorax are fused into one section called a cephalothorax) – this section is protected by a part of the exoskeleton called the carapace
Respiration occurs through structures called gills

16. Class Arachnidia Includes spiders, scorpions, ticks
2 body sections – cephalothorax & abdomen
4 pairs of walking legs (most)
Mouthparts called chelicerae contain fangs – stab & paralyze prey
Mouthparts called pedipalps are used to grab prey
Lack antennae
Spiders all produce silk in organs called spinnerets
All are predators or parasties

17. Class Insecta Compose about 80% of the animal kingdom
Have three separate body regions and three pairs of legs
Only invertebrate capable of flight
Respiration with tracheids, excretion by Malpighian Tubules

18. Circulation
A well developed heart pumps blood through an open circulatory system.
The body cavity that contains the blood is called the hemocoel
In an open circulatory system, blood is NOT always contained in vessels but will pool in spaces called sinuses to bathe organs in blood.

19. Excretion Most have specialized structures called Malpighian tubules.
These remove metabolic wastes from the blood, concentrate the waste into uric acid, and add them to the feces in the intestine before elimination.

20. Response
All have a brain consisting of 2 ganglia which connects to a nerve cord which runs the length of the body.
Well developed sensory organs – many have compound eyes and well developed chemoreceptors (smell/taste)
E.g. dragonfly

21. Why are the insects so successful??
1. Size: tiny to minute - don’t eat much, can hide
2. Exoskeleton: hard, yet great strength
3. Short life span - don’t eat much
4. Reproduction: all sexual - variation
5. Flight: many advantages
6. Specialized appendages: eat many things
7. Adaption of exoskeleton: camouflage etc
8. Well developed sensory ability
9. Evolved social behavior
10. Very specific niches: minimizes competition

23. Ecological Roles of Arthropods
Pollination
Production of honey, wax, and silk
Recycle biological materials to aid in producing topsoil
Form symbiotic relationships with other organisms (see left)
Part of food chain
Burrowing shrimp and Goby fish living in Symbiosis
shrimp cleans and digs a burrow where they both live (shrimp is blind)
When danger approaches, the goby fish touches the shrimp with its tail to warn it and both hide in the burrow

24. Continued
insects help pollinate crops ( example: bees pollinate flowers )
some insects destroy other harmful insects ( Ex: ladybird beetles eat insects which destroy orange and lime crops )
source of food
chemicals that are obtained are used by humans ( ex: chitin from crustacean shells is used to dress wounds and to make thread for surgical stitches )

25. The Largest living Arthropod!
is the Japanese Spider Crab with a leg span of 4 meters and a weight of 20kg.
This crab has a life expectancy of 100 years.