aracteristics that make them better suited to their environment are more likely to survive, reproduce, and pass on the genes for those characteristics. A population of plants reproduces sexually. A new disease spreads through the area. Explain why sexual reproduction could help the population survive. 1. The disease is an environmental change, so plants that were previously well adapted may no longer survive well. 2. Sexual reproduction produces genetic variation, so not all plants will have exactly the same characteristics. 3. Some plants may have inherited genes that make them more resistant to the disease. 4. These resistant plants are more likely to survive and reproduce, so the genes for resistance can become more common in the population over time. ### 2. It allows humans to use selective breeding **Selective breeding** is when humans choose organisms with desired characteristics and breed them together. For example, farmers may select: - crop plants with higher yield - cows that produce more milk - animals with more meat - plants that are more resistant to disease This can speed up the effect of selection because humans choose which organisms reproduce. Sexual reproduction produces variation. Variation gives natural selection something to act on, especially when the environment changes. ## Disadvantages of sexual reproduction Sexual reproduction is not always the best strategy. It usually requires two parents, or at least the production and fusion of gametes. This can take time and energy. For animals, this may involve finding a mate, competing for mates, courtship behaviour, or caring for offspring. For plants, this may involve producing flowers, pollen, nectar, fruit, or seeds. Compared with asexual reproduction, sexual reproduction is often: - slower - less energy efficient - dependent on finding a mate or transferring gametes - less likely to produce large numbers of offspring quickly Variation gives a population a better chance of surviving change, but not every variation is useful. Some variations are harmful, some are neutral, and some are helpful only in certain environments. ## Asexual reproduction **Asexual reproduction** involves only one parent and no fusion of gametes. The offspring are genetically identical to the parent, except for rare mutations. A genetically identical organism is called a **clone**. In many organisms, asexual reproduction happens by **mitosis**, which is cell division that produces genetically identical cells. Asexual reproduction is common in many microorganisms, fungi, and plants. ## Advantages of asexual reproduction ### 1. Only one parent is needed An organism does not need to find a mate. This is a big advantage if the organism is isolated or if mates are rare. ### 2. It is faster and more energy efficient Because there is no need to find a mate or produce gametes for fertilisation, asexual reproduction can be quicker and use less energy. This means many offspring can be produced rapidly. ### 3. It is very useful in favourable conditions If the environment is stable and the parent is well adapted, producing identical copies can be very successful. For example, if a plant is growing well in a sunny area with enough water and minerals, asexual reproduction can quickly produce more plants with the same successful genetic information. Think: **sexual = variation**, **asexual = speed and clones**. ## Disadvantages of asexual reproduction The main disadvantage is lack of genetic variation. If the environment changes, clones may all be affected in the same way. For example, if one clone is vulnerable to a disease, the other clones may also be vulnerable because they have the same genes. Asexual reproduction can