AD Arthropoda and Chelicerata Myriapoda Crustacea

Question 1

What are some characteristics of Arthropods

Answer 1

Bilateral symmetry
Chitinous skeleton - shed during growth
Growth is staggered by moulting
Segmented bodies arranged into regions
Jointed paired appendages eg legs
Nervous system is ventral and the circulatory system is open and dorsal
Many have compound eyes
Tracheal respiratory system and/or book lungs

Question 2

What are Arthropods?

Answer 2

An invertebrate animal having an exoskeleton, a segmented body, and paired jointed appendages
eg insects, arachnids

Question 3

Describe the following:
Epicuticle
Exocuticle
Endocuticle
Gland cell

Answer 3

Epi- Thin, waterproof layer of protein, lipoprotein, lipids, waxes but no chitin
Exo - Protein and alpha chitin together form a complex glycoprotein. Sclerotised where strength and rigidity is required
Endo - less protein, more chitin. Mineralised in crustaceans
Gland - Different types. Secrete waxy epicuticle. Enzymes that promote sclerotisation

Question 4

Describe the nervous and circulatory system in Arthropods

Answer 4

Coelom reduced
Hemocoel is a large body cavity filled with hemolymph that bathes the tissues
Heart is a dorsal muscular tube that pumps blood anteriorly by peristaltic contractions
Heart perforated by paired ostia with one-way valves allowing blood into the heart
In crustacea and chelicerata, blood transports oxygen exchanged at gills or book lungs but in insects, most of the gas exchange is provided in the tracheal system

Question 5

What are the main features of Chelicerates?

eg body plan, NS

Answer 5

Body plan: Prosoma or cephalothorax (the fused head and thorax) +
opisthosoma or abdomen

CHELICERAE: the only appendages in front of the mouth

RESPIRATORY SYSTEM: Marine chelicerates have gills, while terrestrial forms generally have book lungs + tracheae or just tracheae

NERVOUS SYSTEM: Generally, the ganglia of living chelicerates are fused into large masses in the prosoma

Question 6

What are pedipalps?

Answer 6

Resemble the legs, as seen in spiders

Massive pincers, as in scorpions

Question 7

What are scopulae?

Answer 7

dense tufts of hair beneath claws &, in some spiders (e.g.
tarantulas), the whole of the ventral surface of the ‘foot’
• Enable walking on smooth, vertical surfaces
• Adhesion to substratum is due to van der Waals force
• Allows spiders to ‘support’ 170 x their own weight