WAEC SSCE - Biology - 2000 (Practical)
Question 1 Report
1 (a) (i) identify specimens A and B without reasons (ii) Give four differences between specimens A and B.
Using a sharp knife, scalpel or blade, cut specimen B into two equal halves to expose the internal structures.
b. (i) Make a labeled drawing of 8 cm to 10cm long to show the observable internal structures of specimen B.
(ii) State the dispersal mechanism of specimen B.
(C)(i) Identify C, D and E without reasons. (ii) State two features, each of specimen C, D and E which adapt to their habitats.
2. The height (cm) of 20 students in a class are as follows:.155, 157, 151 169, 162, 151, 149, 165, 169,176.169, 179,173, 179, 173, 169, 157, 155, 165, 157, 197 and 162.
Use them to answer the following questions:
(a) Make a frequency distribution table of class interval of five of the different heights (b) what is the modal height? (ii) median height? (ii) mean height?
(c) (i) Construct a histogram showing the variation of height, amongst the students with the heights on the horizontal number of students on the vertical axis.
(ii) How many students fall into each or the height axis and number of students on the vertical axis.
(iii) How many students have height between 155 and 179?
(iv) Find the difference in height between shortest and the tallest students.
(d) (i)What type of variation is height? (ii) Mention three other examples of the type of variation in (d) (i) above.
3.(a) identify specimen F, G, H, I, J, and K without reasons. (b)(i) State one observable feature by which each of specimens F,G and H obtain their food.
(ii) State three observable features which contribute to the survival of specimen I.
(c)Mention two observable characteristics each, of specimens J and K. (ii) Name the two bones, each, which articulates with specimens J and K
(iii) Make a labeled drawing of 8cm to 10 cm long of specimens K.
Answer Details
Question 1 (Specimen study)
(a)(i) Identification — Specimen A is a maize fruit (grain/caryopsis); Specimen B is a tomato fruit.
(ii) Four differences between A (maize grain) and B (tomato fruit):
| Feature | Specimen A (maize grain) | Specimen B (tomato fruit) |
|---|---|---|
| Texture | Dry and hard | Fleshy, soft and juicy |
| Fruit wall (pericarp) | Thin and fused to the seed | Thick, succulent and free from the seeds |
| Number of seeds | One seed only | Many seeds |
| Colour when ripe | Yellow/pale, not brightly coloured | Bright red and attractive |
(b)(i) Cut lengthwise, the tomato shows the following internal structures. A labelled drawing (8–10 cm long) of the longitudinal section is shown below.
(ii) Dispersal mechanism of specimen B (tomato): animal (biotic) dispersal — the fruit is fleshy, brightly coloured and edible, so it is eaten by animals; the small hard-coated seeds pass out undigested in the animal's faeces some distance away.
(c)(i) Identification: C = water lettuce (a floating aquatic plant); D = cactus (a desert plant); E = climbing bean plant (a twining land plant).
(ii) Two adaptive features of each to its habitat:
| Specimen | Two adaptive features |
|---|---|
| C – water lettuce | (1) Light, air-filled spongy tissue that keeps it floating; (2) numerous fine feathery roots hanging in the water to absorb dissolved nutrients. |
| D – cactus | (1) Leaves reduced to spines to cut water loss (and for protection); (2) thick, green, fleshy stem that stores water and carries out photosynthesis. |
| E – climbing bean | (1) Tendrils/twining stem for climbing towards light; (2) broad flat leaves that expose a large surface for photosynthesis. |
Question 2 (Heights of 20 students)
The 20 heights (cm), arranged in order, are: 149, 151, 151, 155, 155, 157, 157, 157, 162, 165, 165, 169, 169, 169, 169, 173, 173, 176, 179, 179.
(a) Frequency distribution table (class interval of 5):
| Class interval (cm) | Heights | Frequency (f) | Mid-value (x) | fx |
|---|---|---|---|---|
| 149 – 153 | 149, 151, 151 | 3 | 151 | 453 |
| 154 – 158 | 155, 155, 157, 157, 157 | 5 | 156 | 780 |
| 159 – 163 | 162 | 1 | 161 | 161 |
| 164 – 168 | 165, 165 | 2 | 166 | 332 |
| 169 – 173 | 169, 169, 169, 169, 173, 173 | 6 | 171 | 1026 |
| 174 – 178 | 176 | 1 | 176 | 176 |
| 179 – 183 | 179, 179 | 2 | 181 | 362 |
| Total | 20 | 3290 |
(b)(i) Modal height: the class 169 – 173 cm has the highest frequency (6), and 169 cm occurs most often, so the modal height is 169 cm.
(ii) Median height: for 20 values the median is the average of the 10th and 11th values. Both are 165 cm, so the median height is 165 cm.
(iii) Mean height: \( \bar{x} = \dfrac{\sum fx}{\sum f} = \dfrac{3290}{20} = 164.5\ \text{cm} \).
(c)(i) Histogram — height (cm) on the horizontal axis, number of students on the vertical axis, with equal-width bars touching one another at heights 3, 5, 1, 2, 6, 1 and 2.
(ii) Number of students in each class: 149–153 = 3; 154–158 = 5; 159–163 = 1; 164–168 = 2; 169–173 = 6; 174–178 = 1; 179–183 = 2.
(iii) Students with height between 155 and 179 cm: all except the three shortest (149, 151, 151), so 17 students.
(iv) Difference between tallest and shortest: \( 179 - 149 = 30\ \text{cm} \).
(d)(i) Height is an example of continuous variation.
(ii) Other examples of continuous variation: body weight, skin colour and intelligence (I.Q.).
Question 3 (Specimens F, G, H, I, J and K)
(a) Identification: F = mosquito; G = butterfly; H = housefly; I = grasshopper; J = humerus; K = femur.
(b)(i) One observable feature by which F, G and H obtain their food:
| Specimen | Feeding feature |
|---|---|
| F – mosquito | Sharp, needle-like piercing-and-sucking proboscis for sucking blood/plant juices. |
| G – butterfly | Long, coiled siphoning proboscis for sucking nectar from flowers. |
| H – housefly | Soft, spongy (sponging) mouthparts for mopping up liquid and dissolved food. |
(ii) Three observable features that aid the survival of specimen I (grasshopper): (1) green body colour that camouflages it among leaves; (2) large, muscular hind legs for jumping away from danger; (3) a pair of wings for flying/escape.
(c)(i) Two observable characteristics each of J (humerus) and K (femur):
| Specimen | Two observable characteristics |
|---|---|
| J – humerus | (1) Long bone with a rounded head at the upper end; (2) a shaft ending in a pulley-shaped, grooved surface at the lower end. |
| K – femur | (1) Longest, strongest bone with a ball-like head set on a distinct neck; (2) two rounded condyles at the lower end. |
(ii) Two bones that articulate with J and K: the humerus (J) articulates with the scapula (at the shoulder) and the ulna (at the elbow); the femur (K) articulates with the pelvic (hip) girdle (at the hip) and the tibia (at the knee).
(iii) A labelled drawing (8–10 cm long) of specimen K (femur) is shown below.
