Phylum Annelida

Question 1

Symmetry;

What symmetry does this animal display?

Answer 1

Bilateral symmetry (though round in transverse section).

Question 2

Support;

All annelids get support from the ___ that fills the space between the outer surface and the gut.

The coelom is fluid filled and acts as a ____

Answer 2

‘additional tissue’.

‘hydrostatic skeleton’.

Question 3

Coelom;

Annelids have coelom, what are these?

Answer 3

Spaces within the tissue that lies between the body surface and the gut wall.

Question 4

Coelom;

1. The ratio of surface area ____

Answer 4

‘to metabolically active tissue is increased’.

This is why there is no need for dorso-ventral flattening as there is not the same requirement to maximise SA:V ratio for respiratory purposes.

Question 5

Coelom;

2. The coelom is fluid filled and acts as a hydrostatic skeleton.

Question 6

Coelom;

3. The muscles involved in locomotion are separated from the gut muscles. This allows movement of the organism and peristalsis to occur independently.

Question 7

Coelom;

4. Provides room for the development of organs.

Question 8

Segmentation;

Annelids are metamerically segmented, the body is divided into a number of similar segments, each with its own body cavity and each containing identical copies of nerve ganglia and muscle blocks.

Answer 8

This allows the muscle blocks to contract independently in a coordinated way, making locomotion more efficient. All body parts are repeated in every segment.

As the annelids have increased in size, there is a circulatory system to distribute oxygen and glucose to every cell (gas exchange surface is the moist body surface).

Question 9

Gut/feeding;

Annelids have a one way gut with a separate mouth and anus, ingested and undigested food do not mix.

Answer 9

There is regional specialisation:
* Muscular pharynx
* Oesophagus
* Crop for storage
* Gizzard for mechanical digestion
* Intestine for absorption

All digestion is entirely extracellular in the gut cavity.