Form 3 Science Chapter 4

Reproduction # The importance of reproduction is to ensures that a particular species does not extinct !!!#

4.1 sexual and asexual reproduction
Reproduction =

involves the production of new generation of individuals of same species.
Sexual reproduction

involve male and female organisms.
Asexual reproduction

involves only one parent.

Asexual reproduction
Binary fission (unicellular organism divides into two equal parts (daughter cells)


Budding (the parent produces an outgrowth or bud which detaches to become a new individual)


Spore formation
Vegetative reproduction
Regeneration (Regrowth of lost or destroyed parts or organs)

Binary fission

Vegetative reproduction
This type of asexual reproduction is seen in many

flowering plants.
Part of a plant detaches and grow into a new plant.
Example: i. Runner ii. Bulb iii. Rhizome iv. Corm v. Stem tuber

i. Runner
A slender, creeping stem that puts forth roots from

nodes spaced at intervals along its length.
The runner bears roots and becomes independent before the parent plant die.
Example : grass, strawberry

ii. Bulb
A short, modified, underground stem surrounded by

usually fleshy modified leaves that contain stored food for the shoot within.
Example : Onion, lilies

iii. Rhizome
A horizontal, usually underground stem that often

sends out roots and shoots from its nodes.
Example: ginger, Canna

iv. Corm
A short, thick, solid, food-storing underground stem,

sometimes bearing papery scale leaves.
Examples: cocoyam , water chestnut

iv. Stem tuber
The swollen ends of underground stems
New shoot sprout out from axillary buds or ‘eyes’.
Example: potato, beet

4.2 The male reproductive system

Secondary sexual characteristics ( male)
Growth of hair on face, chest, in pubic region and

armpits.







Beard Moustache The voice becomes deeper. Body becomes more muscular. Chest becomes broader. Certain mental and emotional changes.

Male gamete (sperm)
The role of the

sperm is to swim towards the ovum and fuses with it to form zygote.
Zygote will

develop into an adult individual.

4.3 The female reproductive system

Female gamete (ovum)
The ovum stores some food in

its cytoplasm.
The food is used to nourish

the embryo which develops from the zygote.

Secondary sexual characteristics ( female)
Growth of hair in pubic region and armpits.
Commencement of menstruation.
Production of ova by the ovaries.
Pelvis becomes broader.
Fat deposits on hip and thighs.
Growth and development of breasts.
Certain mental and emotional changes.

4.4 The menstrual cycle Menstruation is the discharge of the uterus lining and blood through the vagina.

What happen after sexual intercourse ?
Sperms swing to

Fallopian tube.
Only one sperm is needed to fertilise the ovum.
Sperm and ovum fuse to form zygote.
The zygote form a ball of cell called embryo.

Fertilisation
Fertilisation =

The union of male and female gametes to form a zygote.

Growth and development of the foetus in uterus (womb)

Exchange of materials in placenta

New baby

Importance of pre-natal care 1.

Diet Advice: Eat a good healthy diet rich in proteins, calcium and vitamins.

Importance of pre-natal care 2. Cigarette smoke

Importance of pre-natal care 3. Avoid alcohol and drugs