I: | Most sponges work rather like chimneys: they take in water at the bottom and eject it from the osculum ("little mouth") at the top. |
II: | The inner surface is covered with choanocytes where the wave-like motion of the whip-like flagella drives water through the sponge's body. |
1. A sponge | 2. A Cnidarian |
3. A Ctenophore | 4. A flatworm |
A: | I is found in all the molluscs. |
B: | II is a cavity used for egestion, excretion and respiration. |
A | B | C | D | E | F | |
1. | Blood vessel | Nerve cord | Trachea | Spiracles | Crop | Hearts |
2. | Blood vessel | Nerve cord | Trachea | Spiracles | Oesophagus | Hearts |
3. | Nerve cord | Blood vessel | Trachea | Spiracles | Crop | Ostia |
4. | Nerve cord | Blood vessel | Stomo- chord |
Ostia | Oesophagus | Spiracles |
I: | It is a hydraulic system used by echinoderms for locomotion, food and waste transportation, and respiration. |
II: | The system is composed of canals connecting numerous tube feet. |
1. Ascidia | 2. Amphioxus |
3. Petromyzon | 4. Exocoetus |
The figure shows the mouth of a chordate. It can easily be seen that:
I. The mouth is circular | II. Jaw is absent. |
1. Ascidia | 2. Amphioxus |
3. Petromyzon | 4. Exocoetus |