Phylum Arthropoda I Trilobites, Chelicerates, and Myriapods Chapter 19

Question 1

19.1. To what clades above the level of Phylum does Phylum Arthopoda belong?

Answer 1

Clade Bilateria
Clade Protostomia
Clade Ecdysozoa (molting animals; shed cuticle)

Question 2

19.2 Why is Phylum Arthropoda so successful?

Answer 2

– Exoskeleton protects and allows mobility
– Segmented (jointed) appendages = efficient locomotion
– Air piped directly to cells
– Well developed sensory organs
– Complex behavior

Question 3

19.3 What synapomorphies define Phylum Arthropoda?

Answer 3

Synapomorphies:
* Chitinous exoskeleton that is shed
* Jointed appendages

Question 4

19.4 Describe the general body plan and features of arthropods.

Answer 4

• Segmented body (metamerism)
  – Each segment with pair of appendages
  – Segments fused into functional groups (tagmata)
• Eucoelomate (coelom reduced to hemocoel)
• Open circulatory system

Question 5

Uniramous

Answer 5

Uniramous
Unbranched
Myriapoda
+
Hexapoda

Question 6

Biramous

Answer 6

Branched
Crustacea

Question 7

Chelicerae

Answer 7

Grasp or pinch; often fangs
(Chelicerata)

Question 8

Mandibles

Answer 8

Jointed; Chew or grind
(Myriapoda, Hexapoda, Crustacea)

Question 9

tagmata

Answer 9

comprising several adjoining segment

Question 10

19.6 What synapomorphy defines Subphylum Trilobita? How many species exist today?

Answer 10

Subphylum Trilobita†
* Extinct for 245 million years
Synapomorphy:
* 3 longitudinal lobes: 2 lateral pleural lobes
& 1 central axial lobe

Question 11

19.7 What synapomorphy defines Subphylum Chelicerata? What other features are found in
chelicerates?

Answer 11

Subphylum Chelicerata
Synapomorphy:
* 1st pair of appendages are chelicerae (no mandibles)
Other Features:
* 6 pairs of appendages:
* No antennae
* 2 tagmata
– Cephalothorax
– Abdomen

Question 12

19.8 Which organisms belong to Class Merostomata?

Answer 12

crabs; ancient animals

Question 13

Name some organisms in Class
Arachnida

Answer 13

Spiders, ticks, scorpions, mites

Question 14

malpighian tubules

Answer 14

Excretion/osmoregulation