Week 3 - Ecdysozoa

Question 1

What are the classes within Ecdysozoa?

Answer 1

Nematodes - roundworms
Onychophora - velvet worms
Arthropods - insects, crustaceans, Chelicerata

Question 2

What are the primary characteristics of nematodes?

Answer 2

Triploblastic
bilateral symmetry
pseudocoelomate
Cylindrical shape, with tapering at both ends.
Lack cilia
1 longitudinal muscles
covered in cuticles

Question 3

What is the general structures of nematodes?

Answer 3

• Epidermis covered by thick non-cellular cuticle.
  Cuticle:
• comprised of mostly collagen
• high hydrostatic pressure inside pseudocoel
• Movement via thrashing motion.

Question 4

What are the characteristics of Arthopods?

Answer 4

• Bilateral symmetry
• jointed limbs + 1 modified pair for feeding.
• chitinous exoskeleton
• metameric segmentation
• tagmatisation - Segments organised into
  function regions

Question 5

What makes arthropods such a viable class?

Answer 5

• an exoskeleton that is highly protective yet highly flexible.
• segmentation allows for efficient locomotion.
• Air piped directly to cells (allows for high metabolic rate).
• highly developed sense organs (touch, smell, hearing, balance, chemoreception and sight)
• complex behavioural patterns
• limiting intraspecific competition with metamorphosis - larval and adult forms eat different foods and live in different habitats

Question 6

Describe the exoskeleton

Answer 6

• continuous integument (layer)
• chitinous - durable and resistant to nitrogenous polysaccharides.
• Sclerites
• Does not expand as animal grows - requires moulting

Question 7

What are the advantages and disadvantages of an exoskeleton?

Answer 7

ADV:
- protection of soft body parts
- reduction in EWL
- internal projections for sites for muscle attachment
- allows complexity of form and function of appendages
DisADV:
- Restricts growth
- moulting has high energy cost
- the animal is highly vulnerable during moulting process

Question 8

Describe the cuticle

Answer 8

• it is an outer covering to the epidermis
• consists of a relatively thick inner procuticle and a thin epicuticle.
• Epicuticle: comprised of protein and lipids, sclerotization stabilises and hardens the epicuticle.
• The procuticle is divided into the exocuticle (secreted before moulting) and a endocuticle (secreted after a moult).

Question 9

What are the types of metamorphosis?

Answer 9

Exopterygotes: