Asexual Reproduction PDF

# CHAPTER 16 REPRODUCTION ## Reproduction * The processes that make more of the same kind of organism. ## Types of reproduction 1. Sexual reproduction 2. Asexual reproduction ### 1. ASEXUAL REPRODUCTION * Definition: A type of producing new genetically identical offspring from one parent only wit...

# CHAPTER 16 REPRODUCTION ## Reproduction * The processes that make more of the same kind of organism. ## Types of reproduction 1. Sexual reproduction 2. Asexual reproduction ### 1. ASEXUAL REPRODUCTION * Definition: A type of producing new genetically identical offspring from one parent only without producing gametes * **Gametes:** Cells produced from a male and a female to fuse together producing one cell called zygote that divide producing a new organism #### Types of Gametes in animals * Sperm in males * Ovum in females. ### Types of asexual reproduction 1. Binary fission 2. By spores 3. by budding 4. by tubers #### 1. binary fission * Bacteria reproduce by cell division (fission). Any bacterial cell can divide into two and each daughter cell becomes an independent bacterium. * In some cases, this cell division can take place every 20 minutes so that, in a very short time, a large colony of bacteria can be produced. #### 2. by spores in fungi 1. Fungus that reproduces by spores contains two parts that are aerial hyphae and rhizoid. 2. Aerial hyphae contain 2 parts that are sporangium and sporangiophore. 3. Sporangium contains spores. > Diagram of fungus with different parts: > 1. Rhizoid > 2. Spores > 3. Stolon > 4. Sporangium > 5. Sporangiophore #### How a fungus spreads to a new source of food 1. Fungus produces spores in sporangia and spore case which bursts releasing spores that spread by wind. 2. when spores fall on food in suitable conditions such as temperature and humidity, they germinate leading to formation of new fungi. #### 2.Budding in yeast > Diagram of the budding process: > 1. Parent yeast > 2. Bud > 3. New yeast cell > 4. Separated yeast cells > 5. Chain of yeast cells > Fig. 4 Budding in yeast #### Asexual reproduction in potatoes * **Example (Tuber formation in potatoes)** > **What is meant by tuber:** > Short underground stem or root usually much enlarged, and has a storage function. > **Steps of tuber formation:** > 1. In the potato tubers there are grooves called eyes (Each eye contains a bud with scale leaf) > 2. In favorable conditions buds grow using the stored food in the tuber producing new shoot and root. > 3. Roots grow down and the shoot forms leaves. > **Attention** >**Explain Steps of tuber formation** > 1. Underground side stems grow out from the base of the main stem. > 2. Food is stored in the underground stems forming new tubers. > 3. The leaves, stems and old tuber die, but the new tubers remain dormant until the conditions become favorable. > Diagram of a potato plant with: > 1. Germinating eye bud > 2. Potato eye > 3. New shoot > 4. Scar of old stem > 5. Scar of scale leaf ## Advantages and disadvantages of asexual ### Advantages 1. Often rapid because there is no need to find a mating partner 2. Produces identical strains, therefore it is useful if parents are of good strains 3. Can withstand unfavorable conditions using stored food 4. Maintains a good strain exactly with no variation ### Disadvantages 1. Because it is a rapid process therefore it is harmful in case of organisms that produce diseases. 2. No variety in offspring therefore if there is a change in the environment they may all die if unable to be adapted to the environment. 3. Harmful genes in parents will be transferred to the offspring. 4. Overcrowding may take place causing competition for food. ## 2. Sexual reproduction * A process involving the fusion of haploid nuclei to form a diploid zygote and the production of genetically different offspring. ## advantages and disadvantages of asexual reproduction ### Advantages 1. produces new varieties therefore many can be adapted to the changes in the environment. 2. Allows evolution of species. 3. Harmful genes in the parents will not necessarily be handed on to the offsprings. 4. Slower that asexual therefore it does not lead often to overcrowding. ### disadvantages 1. Excellent individuals can not give identical offspring 2. It is a slow process leads to the production of few offspring and this a disadvantage in organisms useful to humans such as the food producing organisms.