Notes

CHAPTER 4: REPRODUCTION
SEXUAL AND ASEXUAL REPRODUCTION
1. Reproduction.
a. Reproduction is a process of generating offspring.
b. Reproduction is a biological process that occurs in all living organisms.
2. Importance of reproduction
a. Reproduction is important for the survival of all living organisms.
b. Reproduction is also important in maintaining continuity of organisms.
Without a mechanism for reproduction, life would come to an end.
3. There are two types of reproduction, sexual and asexual reproduction.
Sexual reproduction
1. Sexual reproduction involves the joining of a male and a female sex cell.
2. Fertilisation:
i. Fertilisation happens when male and female sex cells are physically
joined together.
ii. Fertilisation that happens inside a female’s body is called the internal
fertilisation.
iii. Fertilisation that happens outside a female’s body is called the external
fertilisation
3. Organisms that reproduce sexually are human beings, mammals, reptiles, fish,
birds, insects and some flowering plants.
Asexual reproduction
1. Asexual reproduction does not involve the fusion of male female sex cells.
2. In asexual reproduction, a simple cell is divided by itself to produce an exact
duplicate of an organisms.
3. There are five types of asexual reproduction:
i. binary fission – amoeba, paramecium
ii. budding - hydra
iii. spore formation - fern
iv. vegetative - grass
v. rejuvenation – starfish, flatworm, lizard
4. Organisms that reproduce asexually are:
i. paramecium
ii. hydra
iii. planarian
iv. amoeba
v. starfish
vi. some flowering and non-flowering plants
5. Binary fission:
i. Mature organisms that have reached maximum size perform cell division
to produce two daughter cells.
ii. The daughter cells produced will develop and have the same
characteristics as their parent organism.
iii. The process of binary fission begins with the division of the nucleus,
followed by the division of the cytoplasm.
iv. Examples of organisms that perform binary fission are amoeba,
paramecium and euglena (algae).
6. Rejuvenation (regeneration):
a. Rejuvenation is the replacement or regrowth of missing or injured body
part.
b. For example, if a planarian is cut horizontally, the head will grow a new tail
and the tail section will grow a new head.
c. This way, a planarian that is damaged or cut into several pieces may grow
into many new organisms.
d. Examples of organisms that reproduce via rejuvenation are planarian,
dugesia (flatworm), starfish, lizard tail.
7. Budding:
a. Involves protoplasmic outgrowth containing a nucleus projecting
from the side of the parent cell.
b. The outgrowth will develop and grow to form a new bud.
c. Examples of organisms that undergo budding are hydra, tapeworm
and yeast.
8. Spore formation (sporation):
a. Mature spore are black in colour and produced and stored in the
sporangium.
b. Spores will released when the sporangium bursts. The tiny and
lightweight spores are blown by wind to other places.
c. When a spore is transported to a place with favourable growing
conditions, it will germinate to form new growths.
d. Examples of organisms that perform spore formation are Rhizopus
(bread mould), mosses, mushrooms and ferns.
9. Vegetative reproduction:
a. New plants are produced from existing plant organs or parts of
organisms.
b. The new plants have the same genetic makeup as the original plant.
c. Flowering plants can carry out vegetative reproduction.
d. There are several types of vegetative reproduction:
i. Rhizomes (ginger, lalang, asparagus)
ii. Tubers (potatoes)
iii. Bulbs (onion)
iv. Corms (yam, gladiokus)
v. Runners (strawberries)
vi. Suckers (banana)
e. Examples of plants that carry out vegetative reproduction are:
i. galangal
ii. sweet potatoes
iii. strawberries
iv. ginger
v. potatoes
vi. shallots