1. Arthropods

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

3. 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)

4. Evolution of Arthropods
Fossilized Trilobites
Evolution of Arthropods
Typical primitive arthropod:
many identical segments with a pair of appendages.
Evolution led to fewer segments and specialized appendages
Photo Credit: ©John Canculosi/DRK Photo. Trilobites, such as the fossilized one shown above, were marine arthropods that were abundant more than 500 million years ago. They were divided into many body segments, each with a walking leg.

5. Feeding
Feeding
Includes herbivores, carnivores, omnivores, detritivores, filter feeders, bloodsuckers, and parasites.
Mouth parts adapted to type of food eaten
Pincers, fangs, jaws

6. RESPIRATION Terrestrial arthropods: breathe through tracheal tubes
Air enters and leaves tracheal tubes through spiracles
small openings located along the side of the body.
Spiracles
Tracheal tubes
Tracheal tubes
The grasshopper has organ systems typical of most arthropods. These organ systems carry out functions such as circulation, excretion, response, and movement. Arthropods have several different types of respiratory organs. In insects, tracheal tubes (inset) move air throughout the tissues of the body.

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

8. Circulation and Excretion
Arthropods have a open circulatory system
No distinction between blood and other fluids
Malpighian tubules (terrestrial): saclike organs that extract waste from the blood
Diffusion (aquatic)

9. Response and Reproduction
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

10. Reproduction Separate sexessexual reproduction
Males directly transfer sperm to females
Ex. Barnacle stretches out appendage to local females
Mating occurs after female molts

11. Movement: Groups of well developed muscles coordinate movement
generating force by pulling on the exoskeleton
Muscles flex (bend) or extend (straighten) the joint.
MOVEMENT
This diagrammatic representation shows how muscles attached to the exoskeleton bend and straighten the joints. (Actual muscles are much larger than those shown here.)

12. 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
Molting Cicada Video

13. Groups of Arthropods
Classified by number of body segments and mouth parts
3 major groups
Crustaceans
Spiders and their relatives
Insects and their relatives

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

15. Body Plan of Crustaceans
swimmerets
Cheliped
Cephalothorax
Fusion of head with the thorax
Mandible:
Mouthpart adapted for biting and grinding food
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

17. 1) Small Crustaceans
Copepods- extremely abundant, planktonic, filter feed
Barnacles- usually sessile, filter feed, body enclosed by calcareous plates
Krill- planktonic, shrimp-like, have carapace to cover anterior, filter feed

20. True Crabs Small abdomen and tucked under cephalothorax
V-shape ab. in males
U-shape ab. in females
Largest and most diverse of decapods
Scavengers and predators

22. Male Jonah Crab

23. Female Jonah Crab

24. 2) Chelicerates Horseshoe crabs, spiders, ticks, and scorpions
No antennae
Have mouthparts called chelicerae
2 body sections
4 pairs of walking legs
Divided into 2 main classes:
Merostomata (horseshoe crabs)
Arachnida (spiders, mites, ticks, and scorpions)

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

26. Horseshoe Crab 1. Carapace 2. Telson 3. Compound eye 4. Anterior spine
Five pair of legs

32. 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

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

34. 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

35. 3) Uniramians Centipedes, millipedes, and insects
Characteristics of Uniramians
Have jaws
One pair of antennae
Un-branched appendages
Carnivores

36. Class Insecta (Insects)
Characteristics of Class Insecta
Contains most species of any other animals
Body divided into 3 segments
Head, thorax, and abdomen

37. 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

38. Response Chemical receptors for taste and smell Well developed ears
Compound Eye: made up of many lenses
Detect minute changes in color and movement
Information from eye is assembled in the brain and directs the insects response
Chemical receptors for taste and smell
Located on the mouthparts, antennae, and legs
Sensory hairs: detect movement in surrounding air or water
Well developed ears

40. 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

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

42. Specialized Mouth Parts
Tubelike mouthpart used to suck nectar
Moth

43. 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

44. 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

46. 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.