WAEC SSCE - Biology - 1997 (Essay)

(a) Labelled diagrams of the female reproductive organs

(i) Female reproductive organ of a flowering plant (the carpel / pistil): The diagram below is a longitudinal (vertical) section through a single carpel, showing the parts that make up the female organ.

(ii) Female reproductive organ of a mammal (human female): The diagram below is a front (anterior) view of the human female reproductive system.

(b) Functions of any two of the labelled parts

In (a)(i) - flowering plant:

• Stigma: receives the pollen grains during pollination and provides a sticky, moist surface that traps them and stimulates them to germinate.
• Ovary: encloses and protects the ovules; after fertilisation it develops into the fruit while the ovules become seeds.

(Other acceptable parts: the style is the passage-way through which the germinating pollen tube grows down to reach the ovule; the ovule develops into the seed after fertilisation; the placenta attaches the ovule to the ovary wall and nourishes it.)

In (a)(ii) - mammal:

• Ovary: produces the female gametes (ova) and secretes the female sex hormones oestrogen and progesterone.
• Oviduct (fallopian tube): its funnel-shaped opening receives the released ovum and carries it towards the uterus; it is the normal site of fertilisation.

(Other acceptable parts: the uterus (womb) is where the fertilised egg implants and the embryo develops until birth; the vagina receives the sperm during mating and is the birth canal through which the baby passes.)

(c) Comparison of reproduction in mammals, amphibians and birds

(a) Experiment to compare the water-holding capacity of sandy, loamy and clayey soils

• Materials: three identical filter funnels, three filter papers, three measuring cylinders, equal known masses (or volumes) of dry sandy, loamy and clayey soil, and a fixed volume of water.
• Method: Line each funnel with a filter paper and place each over a measuring cylinder. Put an equal amount of each dried soil into its own funnel. Pour the same measured volume of water (for example 100 cm³) into each funnel at the same time. Allow the water to drain until dripping stops.
• Measure the volume of water that collects (the filtrate) in each measuring cylinder.
• Water retained = volume poured in minus volume drained out.
• Observation/Result: most water drains through the sandy soil (little retained); least water drains through the clayey soil (most retained); loamy soil is intermediate.
• Conclusion: water-holding capacity is highest in clayey soil, intermediate in loamy soil and lowest in sandy soil.

(b) Three factors affecting water-holding capacity of soil

• The size of the soil particles (fine particles hold more water than coarse ones).
• The amount of humus (organic matter) present (humus absorbs and holds water).
• The degree of compaction and the pore spaces (porosity) of the soil.

(c)(i) Characteristics

• Sandy soil: made of large particles; well aerated; drains quickly and holds little water; light and easy to work; low in humus and mineral nutrients; warms up quickly.
• Loamy soil: a balanced mixture of sand, silt and clay; well aerated and drained yet holds enough water; rich in humus and nutrients; the most fertile soil.

(c)(ii) Vegetation supported

• Sandy soil supports desert or savanna vegetation such as cactus, grasses and drought-resistant shrubs.
• Loamy soil supports rich crop plants and dense vegetation (rainforest/farm crops) such as maize, yam, vegetables and most food crops.

(a) Explanation of terms

• (i) First aid: the immediate, temporary treatment or help given to a person who is injured or suddenly taken ill, before the arrival of a doctor or before the victim is taken to hospital.
• (ii) Artificial respiration: the manual or mechanical method of forcing air into and out of the lungs of a person who has stopped breathing, in order to restore normal breathing.
• (iii) Dislocation: the displacement of a bone from its normal position at a joint, so that the ends of the bones are no longer in their correct alignment.
• (iv) Haemorrhage: the excessive escape or loss of blood from a broken (ruptured) blood vessel, either internally or externally.

(b)(i) Three objectives of first aid

• To preserve life (save the life of the victim).
• To prevent the condition from becoming worse (prevent further injury).
• To promote recovery and relieve pain until proper medical help is obtained.

(b)(ii) Procedure for mouth-to-mouth artificial respiration

• Lay the victim on the back and clear the mouth and throat of any obstruction (mucus, food, water).
• Tilt the head backward and lift the chin so that the airway is straight and open.
• Pinch the victim's nostrils closed with the fingers.
• Take a deep breath, seal your mouth firmly over the victim's open mouth, and blow air steadily into the lungs until the chest rises.
• Remove your mouth and let the chest fall (air comes out) while you take another breath.
• Repeat the blowing at about 12 to 15 times per minute (steady rhythm) until the victim breathes on his own or medical help arrives.

(c)(i) Three signs of dislocation

• Severe pain at the affected joint.
• Swelling and deformity (abnormal shape) of the joint.
• Loss of normal movement (the joint cannot be moved) at the joint.

(c)(ii) Two ways of stopping bleeding from an open wound

• Apply direct pressure on the wound with a clean pad or cloth (pressure bandage).
• Apply a tourniquet or press on the pressure point of the artery above the wound, and raise (elevate) the injured part above the level of the heart.

(a) Conservation is the wise and careful management, protection and use of natural resources (such as soil, water, forests and wildlife) so that they are not destroyed, exhausted or wasted, but are preserved for the benefit of present and future generations.

(b) Three reasons for conservation

• To prevent the extinction of plant and animal species and to preserve biodiversity.
• To ensure a continuous supply of natural resources (food, timber, water, medicine) for present and future generations.
• To maintain the balance of nature and protect the environment from degradation such as erosion, flooding and desertification (also for recreation, tourism, research and educational value).

(c) Four methods of conserving each resource

(i) Water

• Building dams and reservoirs to store water.
• Preventing pollution of rivers, lakes and streams.
• Afforestation to protect catchment areas and reduce run-off.
• Recycling waste water and avoiding wasteful use.

(ii) Wildlife

• Establishing game reserves and national parks.
• Making and enforcing laws against poaching and indiscriminate hunting (control of hunting by licences and closed seasons).
• Protecting the natural habitats of animals from destruction.
• Breeding endangered species in captivity (zoos) and restocking.

(iii) Forest

• Afforestation and reafforestation (planting of new trees).
• Controlled or selective felling of trees.
• Prevention and control of bush fires.
• Establishing forest reserves and enforcing forest laws.

(d) Three forest or game reserves in Nigeria

• Yankari Game Reserve (National Park), Bauchi State.
• Kainji Lake National Park, Niger/Kwara State.
• Old Oyo National Park (Oyo State), or Cross River National Park, Cross River State.