Unit 1 – Protochordata (Q&A)
Exam-focused answers for 2M, 5M and 12M questions.
Section A — 2 Marks Questions
Q1. Write two characters of Protochordata.
- Notochord present (whole body or larval stage).
- Dorsal hollow nerve cord present.
Q2. Give one example each of Cephalochordata and Urochordata.
- Cephalochordata → Amphioxus (Branchiostoma)
- Urochordata → Ascidia
Section B — 5 Marks Questions
Q1. General characteristics of Cephalochordata.
- Small, fish-like marine chordates.
- Notochord present throughout life and whole body length.
- Dorsal tubular nerve cord present.
- Filter-feeding through pharyngeal gill slits.
- Example: Amphioxus.
Q2. General characteristics of Urochordata.
- Adults are sedentary, sac-like, covered with tunic.
- Notochord & nerve cord present only in larval stage.
- Show retrogressive metamorphosis.
- Exclusively marine.
- Example: Ascidia.
Section C — 12 Marks Questions
Q1. Structure and life history of Amphioxus.
- External features: elongated, pointed ends, oral cirri, atriopore.
- Digestive system: ciliary mode of feeding, pharynx with gill slits.
- Circulatory system: closed type, no true heart.
- Nervous system: dorsal tubular nerve cord.
- Reproduction: sexes separate, external fertilization.
- Development: indirect, through larval stages.
Q2. Structure and life cycle of Ascidia.
- Adult: sac-like, sessile, covered by tunic, pharynx with gill slits, no notochord.
- Reproduction: sexual, external fertilization.
- Larva: tadpole larva with tail, notochord, dorsal nerve cord.
- Metamorphosis: retrogressive; adult loses chordate features.
Q3. Retrogressive metamorphosis in Urochordata.
- Larva: highly advanced, has chordate characters.
- Metamorphosis: tail & notochord absorbed, nerve cord reduced.
- Adult: sedentary, degenerate.
- Significance: shows evolutionary degeneration from active larva to simple adult.
Q4. Comparative account of Cephalochordata and Urochordata.
| Feature | Cephalochordata | Urochordata |
|---|---|---|
| Notochord | Whole life & body length | Only in larva |
| Adult form | Free-living, fish-like | Sessile, sac-like |
| Nervous system | Dorsal nerve cord in adult | Only in larva |
| Feeding | Filter-feeding | Filter-feeding |
| Example | Amphioxus | Ascidia |
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