1. UNIT 3 – ASEXUAL REPRODUCTION IN PLANTS –PART 1
CAPE BIOLOGY

2. OBJECTIVES You should be able to:
Explain the term asexual reproduction.
Discuss the advantages and disadvantages of asexual reproduction.
Discuss the genetic consequences of asexual reproduction.

3. INTRODUCTION
Reproduction: the formation of a new organism from one or two individuals.
It involves the passing on of genetic material which ensures the survival of a species.
There are two types of reproduction, asexual and sexual reproduction.
Reproduction involves cell division, growth and development.

4. COMPARISON OF TYPES OF REPRODUCTION
ASEXUAL REPRODUCTION
SEXUAL REPRODUCTION
An organism grows an offspring from itself
Two parents
There is no joining of gametes
There is joining of gametes (fertilization)
The new organism is genetically identical to its parent i.e. it does not produce variation.
It is ideal for stable environments if the organisms is adapted to the environment.
The new organism is genetically different to its parent thus it produces variation.
This makes it good for an unstable environment where new adaptations are necessary for survival of offspring.
It involves mitosis
The formation of gametes involves meiosis
Examples – binary fission in the Amoeba, spore production in fungi, bud growth in potatoes
Examples – all vertebrates and most plants

5. ASEXUAL REPRODUCTION
Asexual reproduction involves only one individual.
There is no exchange of sex cells or gametes.
The cell division associated with asexual reproduction is mitosis.
Cells produced by this type of division are identical to the original*. The resulting offspring of asexual reproduction are therefore identical to the original organism or clones of the original.
*There may be slight variation due to mutations e.g. bacteria

6. ADVANTAGES OF ASEXUAL REPRODUCTION
It requires only one organism thus no effort is needed to create ways to exchange gametes.
It can lead to the rapid dispersal of species e.g. fungus and grass
It can be a quick way to reproduce e.g. bacteria and parasites.
In some cases there are more food reserves for the offspring and these have a better chance of surviving.

7. GENETIC SIGNIFICANCE OF IDENTICAL OFFSPRING
Since the offspring of asexual reproduction are genetically identical to the original organism, this type of reproduction is advantageous for those organisms living in stable environments. AGRICULTURAL APPLICATION This is also an advantage for farmers who use asexual reproduction to propagate crops. If the original plant has all the features e.g. disease resistance, grows to good size, tasty, looks good – the offspring will have these features as well.

8. DISADVANTAGES OF ASEXUAL REPRODUCTION
It does not produce genetic variation.
Overcrowding may occur.
If the offspring are dispersed e.g. in the form of spores, some may land where they cannot grow or thrive.

9. SIGNIFICANCE OF LACK OF GENETIC VARIATION
If used for propagation of crop plants, the quality of the crop cannot be improved.
The lack of variation means weaknesses show in the offspring after several generations.
Diseases are automatically passed onto the offspring.

10. REVIEW QUESTIONS Define reproduction. Why is reproduction important?
Compare asexual and sexual reproduction.
What are the advantages and disadvantages of asexual reproduction?
What is the genetic significance of the lack of variation in asexual reproduction?

11. TYPES OF ASEXUAL REPRODUCTION
BINARY FISSION, ASEXUAL SPORE FORMATION, BUDDING, FRAGMENTATION
TYPES OF ASEXUAL REPRODUCTION

12. BINARY FISSION
This occurs in unicellular organisms where two or more identical daughter cells are produced from a single cell. Sometimes the process can occur multiple times and create many offspring e.g. bacteria and the malaria parasite Plasmodium.

13. DISCUSSION QUESTION
Q. Why do you think this is an advantage to bacteria and other parasites? A. Many offspring are lost or destroyed between hosts or by the organism’s immune system. Being able to create large amounts of offspring ensures survival of the species.

14. http://aark. portal. isis
TADPOLES AND FISH
SOURCES OF PICTURES OF FISH AND TADPOLES

15. EXAMPLE - AMOEBA
The Amoeba reproduces by binary fission, a form of asexual reproduction.
The Amoeba stops all activities.
The nucleus begins to divide.
When the division of the nucleus has been completed, the cytoplasm begins to divide.
This division process continues until completion when two daughter Amoebae are formed.

16. EXAMPLE - AMOEBA

17. VIDEO CLIP

18. Encystment occurs when the pond or ditch in which an Amoeba lives in dries up, it forms a cyst around itself to protect it from drying up. When the pond fills with water again, the cyst breaks open releasing many Amoebae into the water. EXCYSTATION is the process where the cyst wall breaks down.

19. ASEXUAL SPORE FORMATION
Spores are small structures which form new organisms. They contain a cell and a small amount of food. Large quantities of spore are produced since so many will land on inhospitable areas.

20. DIAGRAM OF FUNGUS

21. LIFE CYCLE OF FUNGUS – Pencillium sp
Hypha
Conidia produced asexually.
Spores from conidia
Germinating spores with hyphae.
Sexual reproduction stage when male nuclei fuse in male hypha (6) with female nuclei in female hyphae (7). Fusion shown in (8).
Structure (9) asci contain ascospores (10) are produced after fusion of male and female nuclei.
A vesicle is formed (11) which produces conidia which in turn produces asexual spores.

22. BUDDING
A new organisms is formed from an outgrowth of the original. This occurs in plants and some simple organisms

23. DIAGRAM OF HYDRA

24. FRAGMENTATION
An organism breaks into two parts, each of which forms new individuals.
Examples
Ribbon worms
Starfish
Video clip of fragmentation