Describe three substances excreted by the human body, two excretory organs, three benefits of grafting in crop production, and two reasons for the importance of scientific methods, providing one reaso

Here are the answers to question 1:

a) (i) Three substances excreted from the human body:

• Urea
• Carbon dioxide
• Water (as sweat or urine)

(ii) Two organs in humans which perform excretory function:

• Kidneys
• Lungs

b) (i) Grafting in crop production is a horticultural technique where tissues of plants are joined so as to continue their growth together. It involves attaching a scion (upper part of one plant) to a rootstock (lower part of another plant).

(ii) Three benefits of grafting:

• It allows for the combination of desirable traits from two different plants, such as a disease-resistant rootstock and a high-yielding scion.
• It can enable plants to grow in unsuitable soil conditions by using a rootstock adapted to those conditions.
• It can accelerate the fruiting or flowering of plants compared to growing from seed.

c) (i) Two ways in which scientific methods are important:

• They provide a systematic approach to solving problems and making discoveries.
• They ensure that conclusions are based on empirical evidence and can be tested and verified.

(ii) One reason for each laboratory rule:
(α) Do not wear rubber slippers to the laboratory:

• Rubber slippers offer insufficient protection against chemical spills or falling objects like glassware. (β) Close all taps before leaving the laboratory:
• To prevent flooding and conserve water. (γ) Spilled liquids must be cleaned immediately:
• To prevent slips and falls and avoid contamination or damage to equipment/surfaces.

d) (i) Earthing in household wiring is a safety measure where the metal casing of an appliance is connected to the earth (ground) via a low-resistance wire. In case of a fault, if the live wire touches the casing, the current flows to the earth, preventing electric shock and tripping the circuit breaker.

(ii) Two sources of electric power generation:

• Hydroelectric power
• Solar power