(a)(i) Class of specimen C
Specimen C (a cock) belongs to the class Aves (birds).
(a)(ii) Three reasons for placing it in that class
- Its body is covered with feathers.
- Its fore-limbs are modified into wings.
- Its mouth is modified into a horny beak without teeth. (It also has scaly legs and lays hard-shelled eggs.)
(a)(iii) Two food items it feeds on
Grains (seeds) and insects. (It also takes worms and green vegetables.)
(b)(i) Two adaptations for its mode of feeding
- A short, strong, horny beak for pecking and picking up grains and insects.
- Strong, sharp claws on the toes for scratching the surface of the ground in search of food.
(b)(ii) Two adaptations for locomotion
- Fore-limbs modified into wings for flying, with a streamlined body that reduces air resistance.
- Strong, clawed hind limbs for walking, running and scratching, and tail feathers for steering and balancing.
(c)(i) Three observable inheritable characters
Colour of feathers, shape of comb and colour of the wattle. (Size of comb, shape of beak and body size are also acceptable.)
(c)(ii) Test cross to determine whether specimen C is homozygous or heterozygous dominant
White feather colour (W) is dominant over black (w). A white cock may be homozygous (WW) or heterozygous (Ww). To find out, carry out a test cross by mating it with a homozygous recessive black fowl (ww).
Case 1: if specimen C is WW
Parents: WW (white) \( \times \) ww (black)
Gametes: all W \( \times \) all w
Offspring: all Ww - every chick is white.
Case 2: if specimen C is Ww
Parents: Ww (white) \( \times \) ww (black)
Gametes: W and w \( \times \) all w
Offspring: Ww (white) and ww (black) in the ratio 1 white : 1 black.
Conclusion: If all the offspring are white, specimen C is homozygous dominant (WW). If about half of the offspring are black, specimen C is heterozygous dominant (Ww).
