The document describes the phylum Arthropoda, including its characteristics and major subgroups. It covers their anatomy, physiology and life cycles. Arthropods have a hard exoskeleton, jointed appendages and undergo molting to grow. They include insects, spiders, crustaceans and others. The phylum contains millions of species and the document delves into the classification, traits and evolution of these diverse animals.

1. Phylum Arthropoda

2. Phylum Arthropoda
Several million species.
Hard exoskeleton.
Coelomate protostomes.

3. Phylum Arthropoda
Subphylum Trilobitomorpha

4. Phylum Arthropoda
Subphylum Trilobitomorpha
Subphylum Cheliceriformes
Class Chelicerata
Subclass Merostomata (horseshoe crabs)

5. Phylum Arthropoda
Subphylum Trilobitomorpha
Subphylum Cheliceriformes
Class Chelicerata
Subclass Merostomata (horseshoe crabs)
Subclass Arachnida (spiders, scorpions, mites, ticks)

6. Phylum Arthropoda
Subphylum Trilobitomorpha
Subphylum Cheliceriformes
Class Chelicerata
Subclass Merostomata (horseshoe crabs)
Subclass Arachnida (spiders, scorpions, mites, ticks)
Class Pycnogonida (sea spiders)

7. Phylum Arthropoda
Subphylum Trilobitomorpha
Subphylum Cheliceriformes
Subphylum Myriapoda
Class Chilapoda (centipedes)

8. Phylum Arthropoda
Subphylum Trilobitomorpha
Subphylum Cheliceriformes
Subphylum Myriapoda
Class Chilapoda (centipedes)
Class Diplopoda (millipedes)

9. Phylum Arthropoda
Subphylum Trilobitomorpha
Subphylum Cheliceriformes
Subphylum Myriapoda
Subphylum Hexapoda
Class Insecta

10. Phylum Arthropoda
Subphylum Trilobitomorpha
Subphylum Cheliceriformes
Subphylum Myriapoda
Subphylum Hexapoda
Subphylum Crustacea
Class Branchipoda (brine shrimp)

11. Phylum Arthropoda
Subphylum Trilobitomorpha
Subphylum Cheliceriformes
Subphylum Myriapoda
Subphylum Hexapoda
Subphylum Crustacea
Class Branchipoda
Class Maxillopoda
Subclass Copepoda (copepod)

12. Phylum Arthropoda
Subphylum Trilobitomorpha
Subphylum Cheliceriformes
Subphylum Myriapoda
Subphylum Hexapoda
Subphylum Crustacea
Class Branchipoda
Class Maxillopoda
Subclass Copepoda (copepod)
Subclass Thecostraca (barnacles)

13. Phylum Arthropoda
Subphylum Trilobitomorpha
Subphylum Cheliceriformes
Subphylum Myriapoda
Subphylum Hexapoda
Subphylum Crustacea
Class Branchipoda
Class Maxillopoda
Class Malacostraca
Order Decapoda (crabs, lobsters, shrimp)

14. Phylum Arthropoda
Subphylum Trilobitomorpha
Subphylum Cheliceriformes
Subphylum Myriapoda
Subphylum Hexapoda
Subphylum Crustacea
Class Branchipoda
Class Maxillopoda
Class Malacostraca
Order Decapoda
Order Isopoda (isopods)

15. What do Arthropods look like?
Triploblastic, bilateral protostomes
Hard exoskeleton
Specialization of appendages
Jointed appendages
Coelom that acts as an open
circulatory system (heomcoel)
Excretory and gas exchange organs
Sense organs that extend out of cuticle
Growth through molting (ecdysis)
Fig. 15.15

16. How do Arthropods support themselves and move?
Cuticle
Secreted by epidermis
Waxes, lipoproteins, proteins.
Sclerotized - tanning process that hardens
Fig. 15.16

17. How do Arthropods support themselves and move?
Each segment bound by four plates - dorsal tergite, ventral sternite,
and two lateral pleurites.
Muscle bands attach to apodemes.
Appendages segmented with extrinsic or intrinsic muscles.
Fig. 15.15

18. How do Arthropods support themselves and move?
Appendages:
Uniramous or biramous.
Parts are specialized for
different tasks.
Fig. 15.17

19. How do Arthropods support themselves and move?
Joints have thin flexible membrane.
Antagonistic muscles: flexors and
extensors.
Joints in one plane or ball-and-socket.
Exoskeleton has condyles that act as
fulcrums.
Fig. 15.18

20. How do Arthropods support themselves and move?
Walking
Walking involves the coordinated
movement of uniramous
appendages in different planes.
Fig. 15.20

21. How do Arthropods support themselves and move?
Walking
Subphylum Myriapoda Millipedes (Class
Diplopoda) have
two legs per
segment on each
side. Slow but
powerful.
Fig. 18.3
Centipedes (Class
Chilopoda) have
one leg per
segment on each
side. Fast but not
as powerful.

22. How do Arthropods support themselves and move?
Swimming
Flapping phyllopodia
Fig. 15.19
Tail flexion

23. How do Arthropods support themselves and move?
Flying
Hemipterans (flies)
Indirect flight muscles allow wings to beat faster than neural
transmission.
Dorsoventral and longitudinal muscles.
Flexible thorax.
Fig. 17.16

24. How do Arthropods support themselves and move?
“Brain” is 2-3 ganglia with specific
functions.
Ganglionated ventral nerve cord.
Sense organs (sensilla) protrude
out of cuticle.
Can be slit in cuticle.
Membranous drums.
Chemoreceptors with thin cuticle.
Fig. 15. 28

25. How do Arthropods support themselves and move?
Simple ocelli.
Complex lensed ocelli.
Compound eyes made of ommatidia.
Fig. 15.29

26. How do Arthropods grow?
Instars have tissue growth but
no increase in external size.
Proecdysis - old endocuticle
digested by enzymes from
epidermis. Begin secreting
new endocuticle.
Ecdysis - old cuticle splits and
animal wiggles out. Body
swells.
Postecdysis - cuticle hardens.

27. How do Arthropods grow?
Timing of molting. Fig. 17.35
Throughout life - crustaceans.
Periodically until certain size - copepods.
During metamorphosis - insects.
Hemimetabolous - insects hatch looking much like
adults. Nymphs gradually attain adult form.
Holometabolous - young very different from
adults. Pupal stage metamorhosis into adult.
Fig. 17.36

28. How do Arthropods feed and digest?
Complete gut with regional
specialization.
Foregut - food intake, transport,
storage, mechanical digestion
(jaws, pharynx, gizzard).
Midgut - extracellular digestion, Fig. 15.24
nutrient uptake (cecae, digestive
gland, hepatopancreas).
Hindgut - excretion of undigested
material, water reabsorption.

29. How do Arthropods feed and digest? Fig. 19.5
Spider silk
Complex fibrous
protein.
Spinning
apparatus in
opithosome.
Liquid silk produced by glands,
secreted into duct, pass to
spinneret with tubes to outside.
Fig. 19.7

30. How do Arthropods feed and digest?
Threads made of different thicknesses and
combined in different ways for different
functions.

31. How do Arthropods maintain homeostasis?
Fig. 15.25
Circulation and respiration
Open hemocoel as a result of
hard exoskeleton and lack of
internal segmentation.
Muscular heart required since
body movements can’t move
blood.
Hemolymph has amebocytes,
pigments, and some have
clotting factors.

32. How do Arthropods maintain homeostasis?
Circulation and respiration Fig. 15.26
Respiratory structures depend on habitat.
Trachea in Gills in aquatic animals.
terrestrial
insects.
Arachnid book lung.
Fig. 19.18

33. Respiration
Gills
a. General
• gills are evaginations
• typical of aquatic animals
• blood is oxygenated by gills
• oxygen delivered to tissues by blood
b. Crustacean Gills
• crustacean gills are usually associated with appendages
• blood circulates through the gill and is oxygenated
c. Book Lungs
• present in many arachnid orders
• similar to book gills of horseshoe crabs
• oxygen transport from the lungs to the tissues is by blood
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34. Open Circulatory System Closed Circulatory System
34

35. NERVOUS SYSTEM
1. General
nervous system is adapted for the needs of a segmented animal as is
that of annelids
annelid and arthropod nervous systems are similar
the similarities may be convergent
2. Arthropod Ground Plan
ladder like nervous system
dorsal brain in the head
a pair of circumenteric connectives that encircle the gut
a paired, ventral, longitudinal nerve cord
paired segmental ganglia
transverse commissures between ganglia
longitudinal connectives
segmental sensory and motor nerves
35

36. NERVOUS SYSTEM
Side view of body showing relative
position of circulatory (yellow),
digestive (green), and nervous
(blue) systems.
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37. How do Arthropods maintain homeostasis?
Osmoregulation and waste excretion
Closed structure required since open
nephrostome wouldn’t with such a large
hemocoel.
Material uptake depends on filtration Fig. 15.27
pressure and active uptake.
Reuptake of salts and nutrients.
Antennal and maxillary glands in
crustaceans. Produce ammonia
with some urea and uric acid.
Malpighian tubules in arachnids and
insects. Blind tubes extend into
hemocoel and empty into gut.
Produce uric acid.

38. How do Arthropods reproduce and develop?
Most gonochoristic with formal mating and internal fertilization.
Fig. 16.32

39. How do Arthropods reproduce and develop?
Usually some brooding.
Development often mixed with early brooding then larval stages.
Eggs centrolecithal but amount of yolk varies (so does cleavage).
Nauplius larva

40. How do Arthropods reproduce and develop?
Parasitic lifestyles
Fig. 16.16
Fig. 16.25
Rhizocephalan barnalces