(a) (i) Describe epigeal germination of a seed. (ii) In a tabular form, state three differences between epige germination and hypogeal germination. (b)(i) W...

(a)(i) Epigeal germination

Epigeal germination is a type of seed germination in which the cotyledons are carried above the soil surface. This is brought about by rapid elongation of the hypocotyl (the part of the axis below the cotyledons), which arches and pulls the cotyledons out of the soil. The cotyledons then turn green, spread out and function as the first leaves (foliage leaves) carrying out photosynthesis until the true leaves develop. Examples include cowpea, groundnut and castor oil.

(a)(ii) Three differences between epigeal and hypogeal germination

(Example of hypogeal: maize, oil palm.)

(b)(i) Seed dormancy

Seed dormancy is a resting condition in which a viable (living) seed fails to germinate even when the external conditions (water, oxygen and suitable temperature) are favourable, until certain internal or external requirements are met.

(b)(ii) Three ways of breaking seed dormancy

• Scarifying or cracking the hard seed coat (mechanically or by heat/fire) to allow water and oxygen in.
• Soaking the seeds in water or in dilute acid to soften or wear away the seed coat.
• Exposing the seeds to a period of low temperature (chilling) or removing germination inhibitors, or treating with growth hormones such as gibberellin.

(c) Six advantages of using contraceptives in human populations

• They help to control and reduce the rate of population growth (check overpopulation).
• They enable proper child-spacing, improving the health of the mother.
• They reduce maternal and infant mortality.
• They allow parents to have only the number of children they can adequately care for, improving family welfare.
• They help to prevent unwanted pregnancies.
• Some (for example condoms) help to prevent the spread of sexually transmitted infections such as HIV/AIDS.