In stating the classes of specimens J,K and L. Most candidates stated the class of Tilapia as
Pisces and not Osteichthyes, of the toad as Amphibian and Lizard as Reptilian and not Reptilia
and so lost the marks.
In writing the reasons for placing the specimens in their classes some candidates wrote on their
mode of feedings, habitat e.t.c. instead of stating observable features.
Expected answers include:
Class of Specimen J /Tilapia – Pisces
Reason
- Body is covered with scales;
- Presence of paired fins;
- Presence of lateral line(s);
- Presence of operculum/gill cover.
Class of Specimen K/Toad- Amphibia
Reason
- Presence of warty skin;
- Presence of webbed digits;
- Presence of moist skin;
- Absence of bulging eyes;
- Presence of ear drum.
Class of Specimen L/Lizard–Reptiles
Reason
- Presence of dry horny scales on skin;
- Presence of fore and hind limbs with clawed digits;
- Homodont dentition;
- Well developed retractable tongue.
Most candidates performed well on structural adaptation of specimens K/Toad and L/Lizard for escaping predators, but many candidates wrote poisonous gland for toad instead of poison gland and so lost the score .
Most candidates did not perform well in stating the similarities and differences between specimens J and L and the drawing of a lateral view of specimen J/Tilapia
Expected answers include:
Drawing of lateral view of specimen J/Tilapia
Details
Mouth drawn with double line (MD)
Operculum shown (OS)
Scales overlapping backwards (SB)
Lateral line shown (LS)
Labels
Mouth, eye, head, nostril, dorsal fin, causal fin, pelvic fin, operculum, lateral line, anus
(d)(i) Similarities between Specimens J & L
- Presence of eyes;
- presence of nostrils;
- Presence of scales;
- presence of head;
- Presence of tail.
(ii) Differences
J/Tilapia L/Lizard
- Presence of fins Presence of limbs
- Absence of tympanum Presence of tympanum
- Lateral line present Lateral line absent
- Short tail Long tail
- Presence of operculum/gill cover No operculum/gill cover
