1. Arthropods
Chapter 28

2. Animal Classification
Sponges
Cnidarians
Worms
Mollusks
Arthropods
Echinoderms
Invertebrates
Class Arachnida
Class Crustacea
Class Insecta
Arthropods
Animals
Fishes
Amphibians
Reptiles
Ectotherms
(cold-blooded)
Vertebrates
Birds
Mammals
Endotherms
(warm-blooded)

3. 28-1: Characteristics of Arthropods

4. Characteristics Arthropod comes from the Greek words
“arthron” – joint
“pod” – foot
Typical arthropods:
Segmented
Coelomate
Bilateral symmetry
Exoskeleton

5. Characteristics
Appendages – any structure (a leg or an antenna) that grows out of the body of an animal

6. Why Arthropods Must Molt
Exoskeletons cannot grow, so they must be shed periodically
Molting – shedding the old exoskeleton
Before an arthropod molts, a new, soft exoskeleton formed beneath the old one
Cicada

7. Segmentation in Arthropods
Arthropods do not have as many segments as segmented worms
In most groups, arthropods are consisted of three segments
Head
Thorax
Abdomen

8. Segmentation in Arthropods
Some arthropods have two sections
Cephalothorax – A fused head and thorax
Abdomen

9. Arthropods Have Acute Senses
Movement, sound, and chemicals can be detected with great sensitivity by antennae
Antennae are also used for sound and odor communication; can detect pheromones
Atlas moth

10. Arthropods Have Acute Senses
Pheromones – chemical odor signals given off by animals
Some pheromones are used as scent trails (example: the group-feeding behavior of ants)
Many pheromones are important in the mating behavior of arthropods

11. Arthropods Have Acute Senses
Most arthropods have one pair of large compound eyes and three to eight simple eyes
A simple eye is a visual structure with only one lens that is used for detecting light

12. Arthropods Have Acute Senses
A compound eye is a visual structure with many lenses
Compound eyes can detect the movements of prey, mates, or predators, and can also detect colors

13. Arthropods Have Other Complex Body Systems
Arthropods have open circulatory systems and complete digestive systems
Mouth, stomach, intestine, and anus

14. Arthropods Have Other Complex Body Systems
Mandibles – the mouthparts of most arthropod groups include one pair of jaws
The mandibles are adapted for holding, chewing, sucking, or biting

15. Arthropods Reproduce Sexually
Some species (bees, ants, and wasps) exhibit parthenogenesis – a form of asexual reproduction in which a new individual develops from an unfertilized egg
In bees, drones are developed from unfertilized eggs

16. 28-2: Diversity of Arthropods
Diversity of All Animals
About 85% of all known animals are arthropods

17. Additional information

18. Arachnids
Spiders, scorpions, mites, and ticks belong to the class Arachnida
Spiders are the largest group of arachnids
An arachnid has a cephalothorax and an abdomen with six pairs of jointed appendages

19. Arachnids
Chelicerae [kuh-lis-er-uh] – the first pair of appendages located near the mouth (modified pinchers or fangs)
Pincers are used to hold food, and fangs inject prey with poison

20. Arachnids
Pedipalps – the second pair of appendages that is adapted for handling food and for sensing
In male spiders, pedipalps are used to carry sperm during reproduction
The four remaining appendages are adapted as legs

21. Arachnids – Black Widow

22. Crustaceans
Class Crustacea include crabs, lobsters, shrimps, crayfishes, pill bugs, and barnacles
Most crustaceans are aquatic and exchange gases over gills

23. Crustaceans – Red Crab Mating

24. Crustaceans – Red Crab Offspring

25. Centipedes and Millipedes
Centipedes and millipedes have tracheal tubes for gas exchange
Centipedes are carnivorous and eat soil arthropods, snails, slugs, and worms
A millipede eats mostly plants and dead material on damp forest floors

26. Insects Class Insecta is the largest group of arthropods
Insects have three body segments and six legs

27. Insects – Giant Asian Hornets (Invasive Species) vs
Insects – Giant Asian Hornets (Invasive Species) vs. European Honey Bees

28. Insects – Giant Asian Hornets (Invasive Species) vs
Insects – Giant Asian Hornets (Invasive Species) vs. Japanese Honey Bees

29. Insects – Botfly

30. Metamorphosis
Metamorphosis – the series of changes, controlled by chemical-substances in the animal
Two types of metamorphosis:
1. Complete metamorphosis consists of four stages:
Egg
Larva – the free-living, wormlike stage of an insect
Pupa – a period of reorganization in which the tissues and organs of the larva are broken down and replaced by adult tissues
Adult

32. Metamorphosis
Examples: ants, beetles, flies, and wasps

33. Metamorphosis With each molt, it begins to resemble the adult more
2. Incomplete metamorphosis – insects go through only three stages of development
Egg
Nymph – hatches from an egg, has the same general appearances the adult but is smaller
Adult
With each molt, it begins to resemble the adult more
Grasshoppers and cockroaches undergo incomplete metamorphosis

34. Picture of incomplete metamorphosis

35. Collecting Arthropods
1. Pitfall Traps
2. Flying Traps

36. Pitfall Trap
Cup
Water
Soap
Paper plate
Sticks
Labels

37. Flying Trap
Water bottles
Scissors
Twine or yarn
Labels