Classwork Series and Exercises {Biology- SS2}: Reproduction

What is Reproduction?

Reproduction means the act of bringing to life young ones that are of the same species. In other word, reproduction is the creation of a new individual or individuals from previously existing individuals.

Types of Reproduction

There are two types of reproduction. These are:

Asexual Reproduction: Only one organism divides to form new ones.

Sexual Reproduction: Two gametes (male and female) fuse together to form a zygote which later develops to a young one.

ASEXUAL REPRODUCTION

In asexual reproduction, one individual produces offspring that are genetically identical to itself. These offspring are produced by mitosis. There are many invertebrates, including sea stars and sea anemones for example, that produce by asexual reproduction. Common forms of asexual reproduction include:

Binary Fission: This is the division of cell into two. Examples are found in protozoa and bacteria.

Cyst Formation (Multiple Fission): This is the division of cell into many daughter cells especially during adverse weather condition – dry season. Example is seen in plasmodium.

Fragmentation: In this type of reproduction, the body of the parent breaks into distinct pieces, each of which can produce an offspring. Planarians and spirogyra exhibit this type of reproduction.

 

Vegetative Propagation: There are two types – Natural  and Artificial vegetative propagation.

Natural Vegetative Propagation: this s the use of natural parts of plants to reproduce and get new individuals. Such part includes stems, leaves and roots. Forms of natural vegetative reproduction are:

• Planting of creeping stems e.g. elephant grass.
• Planting of underground stems and shoots such as rhizomes e.g. spear grass, ginger and canalily.
• Corms e.g. gladiolus, crocus corm and cocoyam.
• stem tubers e.g. irish potato, tiger nuts
• Suckers e.g. banana, plantain and pineapple.
• Bulbs e.g. onion is one of many forms of natural vegetative reproduction.

 Artificial Vegetative Propagation: This involves the use of intelligence by man to grow new plants from cut portion of the vegetative body of an older parent plant. It can be carried out by:

1. Cutting e.g. cassava, cane sugar and most garden shrubs.
2. Layering e.g. bougainvillea, cocoa and cola
3. Grafting e.g. Orange, grapefruit
4. Marcotting e.g. mango

Diagram of artificial vegetative propagation

Advantages and Disadvantages of Asexual Reproduction

Asexual reproduction can be very advantageous to certain animals. Animals that remain in one particular place and are unable to look for mates would need to reproduce asexually. Another advantage of asexual reproduction is that numerous offspring can be produced without “costing” the parent a great amount of energy or time. Environments that are stable and experience very little change are the best places for organisms that reproduce asexually. A disadvantage of this type of reproduction is the lack of genetic variation. All of the organisms are genetically identical and therefore share the same weaknesses. If the stable environment changes, the consequences could be deadly to all of the individuals.

EXERCISES

Lets see how much you’ve learnt, attach the following answers to the comment below

1. One of the following is not an example of asexual reproduction (a) stem cutting (b) grafting (c) conjugation (d) layering
2. Hydra reproduces asexually by (a) budding (b) binary fission (c) Multiple fission (d) Vegetative propagation
3. Multiple fission occurs in this organism (a) Paramecium (b) Plasmodium (c) Amoeba (d) All the above
4. Sugarcane is normally grown by ______________. (a) grafting (b) cutting (c) budding (d) marcotting
5. Vegetative propagation in Bryophyllum is by ___________. (a) leaf (b) stem (c) root (d) all of the above

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