1. Arthropods
Chapter 28

2. Arthropod characteristics
Segmented bodies
Tough exoskeleton made of chitin
Multiple shapes and textures
Jointed appendages: legs and antennae

3. Arthropod evolution
Modern arthropods have fewer body segments and more specialized appendages.
Fossil of a Trilobite, extinct class of Arthropod

4. Fossil of Leanchoilia, Phylum Arthopoda
gallery/gallery.htm

5. Feeding
Herbivores, carnivores, omnivores, parasites, blood suckers, filter feeders, and detritovores
Variety of mouthparts: pincers, fangs, sickle-shaped jaws, feeding tubes
stag beetle pincers

6. Respiration Most arthropods Some arthropods (including spiders)
Tracheal tubes: branching network of tubes that deliver and expel air through spiracles
Some arthropods (including spiders)
Book lungs: layers of respiratory tissue stacked like pages of a book

7. Circulation
Open circulatory system: heart pumps blood to tissues, sinuses, and cavities but does not return to the heart directly

8. Excretion
Malpighian tubules: saclike organs that extract wastes from blood and then add them to feces to move through the gut

9. Chrysina quetzalcoatli is freed in Cusuco National Park, leaving a fecal trail
National Geographic

11. Response Sensitive sensory organs (sight, smell, touch)
Well-developed nervous system
Brain
Ventral nerve cord
Ganglia: groups of nerve cells

12. Movement Flexor muscles Extensor muscles
Muscle pulling against exoskeleton enables movement

13. Reproduction Terrestrial arthropods: internal fertilization
Male places sperm in female
Sperm sac that female picks up
Aquatic arthropods: internal or external fertilization

14. Growth and development
Molting: period of shedding exoskeleton when outgrown
Glands secrete digestive enzymes to break down exoskeleton.
Glands secrete new exoskeleton.
Vulnerable stage
Insect molting case left on tree bark

15. Arthropod subphylums Crustaceans Spiders and their relatives
Insects and their relatives

16. Crustacean characteristics
Two pairs of antennae
Two or three body sections
Mandibles: chewing mouthparts
Body plan: celphalothorax, abdomen, carapace
Barnacles have “lost” appendages.
Decapods have chelipeds and swimmerets.
Ex: shrimp, lobster, crayfish

17. The Anatomy of a Crayfish
Section 28-2
Abdomen
Tail
Swimmerets
Carapace
Cheliped
Mandible
Second antenna
First antenna
Cephalothorax
Walking legs

18. Subphylum Crustacea – hermit crab

19. Subphylum Crustacea –crab

20. Subphylum Crustacea – fire shrimp

21. Chelicerate characteristics
Four pairs of walking legs
Chelicerae mouthparts: fangs that sting and pedipalps that grab prey
Two body sections: cephalothorax and abdomen
Classes: Merostomata (horseshoe crabs) and Arachnida (spiders, scorpions)
Spiders have spinnerets, silk glands.

22. The Anatomy of a Spider Figure 28–9 Section 28-2 Cephalothorax Abdomen
Eyes
Brain
Pumping stomach
Heart
Intestine
Ovary
Malpighian tubules
Anus
Spinnerets
Silk glands
Spiracle
Bases of walking legs
Fanglike chelicera
Pedipalp
Poison gland
Airflow
Book Lung
Figure 28–9 

23. Subphylum Arachnida – black widow spider

24. Scorpion

25. Gum shoe spider web Theridae family
National Geographic
Photo by Darlyne A. Murawski

27. Uniramia characteristics
Jaws
One pair of antennae
Unbranched appendages
Groups: centipedes, millipedes, insects

28. Millipede

29. Centipede

30. Why insects are evolutionarily successful
Flight
Variety of stimuli responses
Differential feeding methods between young and adult
Different morphology between young and adult

31. Insect characteristics
Compound eyes
Some with wings
Three part body plan
Three pairs of legs
Sensitive taste and smell receptors
Three appendages for mouth, including pair of mandibles

32. The Anatomy of a Grasshopper
Section 28-1
Antennae
Compound eye
Brain
Digestive tract
Malpighian tubules
Heart
Reproductive organs
Anus
Spiracles
Tracheal tubes
Nerve cord
Ganglia
Salivary glands
Mouth
Ventral View
Legs
Tracheal tubes
Spiracles
Figure 28–4 

33. Insect life cycle
Metamorphosis: process of changing shape and form from juvenile to adult stage
Incomplete: juvenile stage (nymphs) appear like adults, just smaller
Complete: juvenile stage (larvae) becomes pupa, final stage before becoming an adult

34. Incomplete Metamorphosis Complete Metamorphosis
Section 28-3
Adult
Adult
Eggs
Eggs
Incomplete Metamorphosis
Complete Metamorphosis
Larva
Adult
Nymph
Nymph
Immature
Larva
Nymph
Adult
Pupa
Figure 28–18 

35. Insects and humans
Although they can be a nuisance or pest, insects are significant to agriculture.
They facilitate flower pollination.

36. Insect communication and societies
Chemical cues: pheromones
Visual cues: light, flight patterns
Some insects form societies where castes, groups of individuals, perform specific tasks.

37. Polyphemus moth Pheromone chemical: (E,Z)-6,11-Hexadecadienyl acetate
National Geographic
Image  by Joseph Scheer

39. Subphylum Insecta – lady bug

40. Subphylum Insecta – bee moth