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All the modes of reproduction that we have discussed so far allow new generations to be created from a single individual. This is known as asexual reproduction. Q U E S T I O N S 1. How does binary fission differ from multiple fission? 2. How will an organism be benefited if it reproduces through spores? 3. rise to new individuals through regeneration?anisms cannot give 4. Why is vegetative propagation practised for growing some types of plants? ? 5. Why is DNA copying an essential part of the process of reproduction? 7.3 SEXUAL REPRODUCTION We are also familiar with modes of reproduction that depend on the involvement of two individuals before a new generation can be created. Bulls alone cannot produce new calves, nor can hens alone produce new chicks. In such cases, both sexes, males and females, are needed to produce new generations. What is the significance of this sexual mode of reproduction? Are there any limitations of the asexual mode of reproduction, which we have been discussing above? 7.3.1 Why the Sexual Mode of Reproduction? The creation of two new cells from one involves copying of the DNA as well as of the cellular apparatus. The DNA copying mechanism, as we have noted, cannot be absolutely accurate, and the resultant errors are a source of variations in populations of organisms. Every individual organism cannot be protected by variations, but in a population, variations are useful for ensuring the survival of the species. It would therefore make sense if organisms came up with reproductive modes that allowed more and more variation to be generated. While DNA-copying mechanisms are not absolutely accurate, they are precise enough to make the generation of variation a fairly slow process. If the DNA copying mechanisms were to be less accurate, many of the resultant DNA copies would not be able to work with the cellular apparatus, and would die. So how can the process of making variants be speeded up? Each new variation is made in a DNA copy that already has variations accumulated from previous generations. Thus, two different individuals in a population would have quite different patterns of accumulated variations. Since all of these variations are in living individuals, it is assured that they do not have any really bad effects. Combining variations from two or more individuals would thus create it would involve two different individuals. The sexual mode of since How do Organisms Reproduce? 119 Reprint 2026-27