PART 1 : Asexual vs. Sexual Reproduction [ 4 marks ]
- Discuss the differences between, and the advantages and disadvantages of sexual and asexual reproduction :
Sexual Reproduction is the formation of a new organism from two parents usually, and involves the joining of gametes [ e.g. sperm, pollen, egg] to form a single cell called a zygote [ or fertilised egg ]. The offspring are similar, but not identical to the parents. Sexually Reproductive organisms include mammals, most reptiles, and flowering plants. ADVANTAGES
There is greater genetic variation of the offspring and therefore, greater chance of survival in changing environments. Asexual Reproduction is the process by which a single organism produces a new organism identical to itself. An asexually reproducing organism does not require a partner to produce offspring. It is a process that requires no fusion of gametes whatsoever. Asexually Reproductive organisms include bacteria, nonflowering plants and some reptiles. DISADVANTAGES
Some disadvantages of sexual reproduction are the facts that it requires 2 parents, so if one species dies out, they can no longer reproduce. Sexual reproduction also poses risks of mutations and hereditary diseases. Sexual reproduction is also not as rapid as asexual reproduction. Energy is also expended in finding a mate in many organisms. However some organisms have both male and female reproductive organs that are able to produce gametes simultaneously.
Asexual reproduction is the formation of a new organism when there is the presence of a single parent and no joining gametes [ e.g. sperm, pollen, egg ]. The offspring has identical genes and chromosomes to the parent. ADVANTAGES
No energy is expended in finding a mate.
there is a high chance of survival of the offspring, if the offspring remains near the parent in a stable environment. DISADVANTAGES
Less genetic diversity gives the offspring a lesser chance of survival if the environment changes.
- Discuss the relevance of mitosis and meiosis to sexual and asexual reproduction ;
Mitosis is the asexual form of reproduction, Meiosis being the sexual form. Mitosis involved replicating the Chromosomes of the cell and placing the exact replicas in the daughter cells, resulting in 2 cells.
This is asexual reproduction because the cells are exactly the same. Meiosis involved replication of the chromosomes, random mixing of them and division into 2 cells, duplication and random mixing again and then division into two more cells resulting in 4 cells. This is sexual reproduction because the cells are not exactly the same.
- Include examples of the different types of asexual reproduction ;
1. Binary Fission [ Bacteria and Amoeba ] occurs when a cell simply grows larger, replicates its DNA in genes and chromosomes, and then forms a cell membrane down the midsection of the cell to form two new “ daughter” cells.
2. Budding [ Of Yeast and Hydras ] occurs when a small part of the parent’s body separates from the rest of the rest and develops into a new individual, eventually either becoming an independent organism or part of an attached colony.
3. Spore Formation [ e.g. of Ferns, Malaria – Causing Protozoan called Plasmodium ] occurs where special cells with resistant coverings form. These coverings are resistant to unfavourable environmental conditions such as heat or dryness.
4. Fragmentation [ e.g. of Flatworms and Starfish ] occurs when a parent body is broken into pieces and each piece may form a new individual.
5. Regeneration [ Of Many Plants ] occurs when part of an organism grows to form other organisms that are often still connected to the original organism. Examples of regeneration in plants are the vegetative propagation of runners, of grasses, strawberries, rhizomes in ferns, tubers in potatoes and growing plants from cuttings.
6. Parthenogenesis [ e.g....