1. Examination Guidelines 2011
REPRODUCTION
Lorraine Kuun, July 2011

2. COMPARING ASEXUAL AND SEXUAL REPRODUCTION
Definition of asexual reproduction:
No fertilisation
Only one parent
No genetic variation
as opposed to ...
Lorraine Kuun, July 2011

3. SEXUAL REPRODUCTION Fertilization Two parents Genetic variation
Gametes fuse to form zygote, containing genes from both parents.
Further variation brought about by:
Crossing over during meiosis, prophase I
Random segregation
Random fertilisation
Mutations
Lorraine Kuun, July 2011

4. Types of asexual reproduction
1. Binary fission – “splitting in two” – mitosis, e.g. bacterium: Escherichia coli
Escherichia coli is a bacterium living in the colon of mammals. The bacteria find a home and food in our colons and in its turn they provide us with vitamin K, important for the clotting of blood. This is an example of a mutualistic symbiotic relationship.
Lorraine Kuun, July 2011

5. Types of asexual reproduction
2. Budding – new individual develops as outgrowth on parent organisms e.g. Yeast cells.
Lorraine Kuun, July 2011

6. Types of asexual reproduction
3. Spore production – spores produced during favourable conditions e.g. Fungi
Lorraine Kuun, July 2011

7. Types of asexual reproduction
4. Vegetative reproduction – vegetative part of plant, i.e. root, stem of leaf develops into new plant; can be natural or artificial.
Onion bulb
Lorraine Kuun, July 2011

8. Buds on leaf margins e.g. Kalanchoe
Lorraine Kuun, July 2011

9. Vegetative reproductive organs:
1. Stems: cuttings, stolons, corms, bulbs, rhizomes, stem tubers
2. Roots: root tubers
3. Leaves: buds
Lorraine Kuun, July 2011

10. ARTIFICIAL VEGETATIVE REPRODUCTION IS IMPORTANT IN AGRICULTURE
Lorraine Kuun, July 2011

11. ADVANTAGES OF ASEXUAL REPRODUCTION
Large number of offspring
Reproduction process is fast
Energy expenditure low – no mates needed, no gametes produced
Offspring well-adapted to environment in which parent lives
ONE CONDITION: environment must be favourable
Lorraine Kuun, July 2011

12. What does “favourable environment” mean?
In case of unicellular or more simple organisms e.g.
bacteria and fungi:
1. Enough moisture
2. Suitable temperature (usually warm)
3. Not too much light/ darkness
4. Enough food
In case of others optimal growing conditions may differ.
Lorraine Kuun, July 2011

13. DISADVANTAGES OF ASEXUAL REPRODUCTION
Salmonella Bacteria
Lorraine Kuun, July 2011

14. No genetic variation – adaptation may be difficult
All share same “weak characteristics” – may die out when environmental conditions change/become unfavourable
Mass reproduction can threaten environment – carrying capacity
Background picture that of Anthrax bacteria amongst white blood cells
Lorraine Kuun, July 2011

15. ADVANTAGES OF SEXUAL REPRODUCTION Genetic variation
Possible better adaptations to changing environment
Role in natural selection
Better chances of survival
Lorraine Kuun, July 2011

16. DISADVANTAGES OF SEXUAL REPRODUCTION
High energy cost – gametes to be produced, gestation, parental care etc.
Needs two parents
Slower, longer process
Young can be vulnerable to predators
Extended periods of parental care
Plants may need pollinators
Lorraine Kuun, July 2011

17. In many organisms asexual reproduction is the norm,
but sexual reproduction can occur during unfavourable conditions e.g Fungi – bread mould
Lorraine Kuun, July 2011