Annelida

Question 1

What are annelida?

Answer 1

Metamerically segmented organisims. They were the 1st organisims with a closed circulatory system. They display triploblastic condition and are bilaterally symmetrical.

Question 2

What are the general features of annelida? (5)

Answer 2

1. They display metamerism.
2. They have epidermal chitinous setae which are bristle like projections found on chetae which aid in locomotion, anchorage and anti predation.
3. They have fleshy pseudopodia appendages which aid in locomotion.
4. They are eucoelomates with a schizocoel body cavity ie. fluid coelom surrounding mesoderm layer acting as hydroskeleton providing definite shape.
5. They are covered with a thin cuticle that they periodically molt, beneath which is a contractile body wall which comprises of circular and longitudinal muscles.
6. They have various tactile organs like, tastebuds, photoreceptors, statocysts etc.

Question 3

What does the annelid nervous sytem comprise of?

Answer 3

A supra pharyngyl ganglion, circum pharyngial connectives, double nerve ventral cord, and a segmented ganglia.

Question 4

What does the annelid digestive system comprise of?

Answer 4

It is tube like, with incomplete development.

Question 5

What does the annelid reproductive sytem comprise of?

Answer 5

It may be mono or di oecious gonads may form from coelomic epithilial cell or trochophore larva.

Question 6

Classification of annelids?

Answer 6

Occurs on the basis of number of setae, the presence of parapodia and clitellum.
CLASS:
1. Polychaeta
2. Oligochaeta
3. Hirudinea
4. Archiannelida

Question 7

General features of polchaeta?

Answer 7

1. Multiple chaeta.
2. Mostly marine and carnivorous.
3. Elongated and segmented bodies with lateral fleshy parapodia that have setae.
4. Distinct head with prostomium and peristomium - which bear tactile organs.
5. No clitellum it is monoecious requiring external fertilization with the help of trochophore larva.

Question 8

General features of oligochaeta?

Answer 8

1. Has few chaeta.
2. Mostly terrestrial.
3. Distinct head, eyes, parapodia and tentacles are absent. Pharynx without jaw present.
4. Setae arranged segmentally on the body.
5. Clitellum present so internal fertilization - hermaphrodites with direct development.

Question 9

General features of Hirudinea?

Answer 9

1. Typically aquatic and ectoparasitic in nature.
2. They have a cylindrical, dorsi ventrally flattened body. Have both anterior and posterior ventral suckers.
3. Definite number of segments and annuli.
4. Absence of parapodia and setae.
5. They are hermaphrodites that display direct development.

Question 10

General features of Archiannelida?

Answer 10

1. Primitive annelid form
2. Typically marine
3. Elogated body, setae and parapodia absent with faint external segmentation. It has 2-3 tentacles on prostomium.
4. Monoecious so it requires external fertilization through trochophore larva.

Question 11

What is clade clitellata?

Answer 11

1. Combination of oligochaeta and hirudinea.
2. Presence of clitellum, ring of sectreatory cells which are permanent in oligochaeta but visualized only in vegitative season.
3. Absence of parapodia.
4. Hermaphrodites that have direct development and secrete a coccoon from which worms arise.