1. Phylum Arthropoda “arthro” = jointed “pod” = foot, appendage
largest phylum of animals on Earth; 3 of 4 animals are some kind of arthropod
chitinous exoskelton
grow by molting exoskelton
Most are small because shell limits size
Somites fused or combined into functional groups or tagmata
Most common arthropods are insects (on land) and crustaceans (in the ocean)

2. Why have arthropods achieved such great diversity and abundance?
Versatile exoskeleton
Segmentation and efficient locomotory appendages
Efficient tracheal respiratory system
Highly developed sensory organs
Complex behavior patterns
Reduced competition through metamorphosis

3. Figure 13_02

4. Ecdysis – process of an arthropod shedding its exoskeleton for reasons of growth and repair of injuries
“soft-shelled crab”

6. Figure 13_03

7. Figure 13_04

8. Subphylum Crustacea
                                                         
Great variety of forms; most familiar are shrimp, crabs, lobster
2 pair of antennae, calcified exoskeleton, gills
Some freshwater, but most are marine

9. Less familiar groups of crustaceans
Copepods – abundant as zooplankton; use enlarged antennae for limited movement

10. Less familiar groups of crustaceans
Barnacles – sessile filter feeders
attach to any number of hard surfaces
filter using feathery cirri
Surrounded by plates forming a shell

12. Less familiar groups of crustaceans
Amphipods – laterally compressed body
Small; slightly larger than rice grain
Many found on beaches in seaweed

13. Less familiar groups of crustaceans
Isopods – dorsoventrally flattened
Variable in size from rice to shoebox
One kind eats wood (gribble), another is parasitic (fish lice)

14. Deep sea isopod – “big”
                                                                  

16. Less familiar groups of crustaceans
Krill – planktonic and shrimp-like
up to about 2 inches long
primarily in polar waters
important food source for many whales, penguins, and fish

17. Decapods – “10 legs”
shrimps, lobsters, crabs; largest group of crustaceans in numbers and physical size
first pairs of legs usually claws
shrimps typically scavengers; many are symbionts as cleaners with fish and anemones
lobsters are mainly nocturnal and are either scavengers or predators of molluscs
hermit crabs use snail shells to protect soft abdomen
True crabs with abdomen tucked under shell; scavengers or predators; swimming crabs vs. walking crabs

19. Red-banded coral shrimp

20. Penaeid shrimp – “eatin’ shrimp”

26. male
female

27. Giant hermit crab

30. Subphylum Trilobita Extinct for about 200 million years
Larval horseshoe crabs closely resemble trilobites

31. Subphylum Chelicerata
Ancient group; horseshoe crabs, sea spiders, spiders, ticks, scorpions
Two tagmata (carapace and abdomen)
Six pairs of appendages; 1 pair chelicerae, 1 pair pedipalps, 4 pairs of walking legs
No mandibles or antennae
Most suck liquified contents of prey

32. Class Merostomata horseshoe crabs only extant members of this group
widespread; mainly found in shallow waters with soft bottoms
forage in mud for worms or scavenge
Possess a protective carapace and long spinelike telson
Abdomen possesses layered book gills

34. Class Arachnida
Possess six pairs of appendages, the most anterior of which are the chelicerae (fangs in spiders)
Spiders with cephalothorax and abdomen unsegmented and connected by slender pedicel; possess poison and spin silk; have book lungs
Scorpions with short cephalothorax that bears the appendages and a segmented abdomen ending in a stinging apparatus
Ticks and mites with fused cephalothorax and abdomen; most abundant arachnids; many are disease vectors and plant pests

35. Scorpion Dust mite Web-building spider 50 µm Fig. 33-31
Figure Arachnids
Web-building spider

36. Stomach Intestine Heart Brain Digestive gland Eyes Ovary Poison gland
Fig
Stomach
Intestine
Heart
Brain
Digestive
gland
Eyes
Ovary
Poison
gland
Figure Anatomy of a spider
Book lung
Anus
Gonopore
(exit for eggs)
Chelicera
Pedipalp
Spinnerets
Sperm
receptacle
Silk gland

37. Subphyla Myriapoda and Hexapoda (formerly Uniramia)
The myriapods include centipedes and millipedes
The hexapods include the insects

38. Subphylum Myriapoda
The myriapods pods consist of a head and an elongated, segmented trunk
Possess many uniramous appendages
Single pair of antennae, mandibles, and one or two pair of maxillae
Consists of the Classes Chilopoda (centipedes) and Diplopoda (millipedes)

39. Class Chilopoda - Centipedes
Centipedes are active predators with fangs that inject venom
Possess one pair of appendages per segment
Prefer hiding under logs or rocks in moist environments

40. Class Diplopoda - millipedes
Harmless and herbivorous or detritivorous, prefer same environments as centipedes
Possess two pair of legs per trunk segment
For defense may release toxic fumes or taste bad

41. Insects
Subphylum Hexapoda, insects and relatives, has more species than all other forms of life combined
They live in almost every terrestrial habitat and in fresh water
The internal anatomy of an insect includes several complex organ systems

42. Abdomen Thorax Head Compound eye Antennae Heart Cerebral ganglion
Fig
Abdomen
Thorax
Head
Compound eye
Antennae
Heart
Cerebral ganglion
Dorsal
artery
Crop
Anus
Vagina
Figure Anatomy of a grasshopper, an insect
Malpighian
tubules
Ovary
Tracheal tubes
Mouthparts
Nerve cords

43. Insects diversified several times following the evolution of flight, adaptation to feeding on gymnosperms, and the expansion of angiosperms
Insect and plant diversity declined during the Cretaceous extinction, but have been increasing in the 65 million years since

44. Flight is one key to the great success of insects
An animal that can fly can escape predators, find food, and disperse to new habitats much faster than organisms that can only crawl

45. Many insects undergo metamorphosis during their development
In hemimetabolous (incomplete) metamorphosis, the young, called nymphs, resemble adults but are smaller and go through a series of molts until they reach full size

46. Insects with holometabolous (complete) metamorphosis have larval stages known by such names as maggot, grub, or caterpillar
The larval stage looks entirely different from the adult stage

47. (a) Larva (caterpillar) (b) Pupa (c) Later-stage pupa (d) Emerging
Fig
(a) Larva (caterpillar)
(b) Pupa
(c) Later-stage
pupa
Figure Metamorphosis of a butterfly
(d) Emerging
adult
(e) Adult

48. Most insects have separate males and females and reproduce sexually
Individuals find and recognize members of their own species by bright colors, sound, or odors
Some insects are beneficial as pollinators, while others are harmful as carriers of diseases, or pests of crops
Insects are classified into more than 30 orders

49. Fig a
Figure Insect diversity

50. Fig b
Figure Insect diversity

51. Fig c
Figure Insect diversity

52. Fig d
Figure Insect diversity

53. Fig e
Figure Insect diversity