Question

1) Discuss the difference between the role of the cuticle in the nematode and the earthworm.

2) What is the advantage of segmentation?

3) Adaptive radiation has resulted in high morphological diversity amongst the phylum Annelida. Feeding adaptations show great variation. Discuss this statement giving at least three examples of different feeding methods found within this phylum

4) The term the “Good, the Bad and the Ugly” has often been applied to the phylum Nematoda.   Give an example of a genus within this phylum that would match each of the above terms. Briefly, explain why you selected this Genus.  

Answer 1

1)

The cuticle is an extracellular matrix that contains extensively linked collagen-like proteins. It forms provides shapes to nematodes as well as serves as a barrier from the environment. In earthworms cuticle largely prevents drying of the earthworm and also prevents abrasion from the soil.

2)

Segmentation allows sophisticated means of movement. It allows organisms to have a complex body structure and advanced functions. Research identifies segmentation to provide organisms with an evolutionary advantage as well given to the ability to perform complex functions.

3) Three familiar types of feeding structures found within Annelids are are

• eversible pharynx (polychaetes)
• jaw-like structures for seizing and biting off pieces of vegetation or decaying matter (ex- phyllodocidae and Eunicidae)
• "crowns" of cilia covered palp for filter feeding (sabella)

Annelids live in a variety of habitats- terrestrial, ponds, marine environments etc. Thus they evolve features to best suit their feeding needs according to their availability. When an organism living in different habitats (ecological niches) evolves features different from one another it is called the adaptive radiation.

4)