NCERT Solutions class 10 Science Chapter 9 || Heredity and Evolution Solution Class 10 Science Chapter 9 || Heredity and Evolution Solution || Biology || Science ||

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Ques 1: If a trait A exists in 10% of a population of an asexually reproducing species and a trait B exists in 60% of the same population, which trait is likely to have arisen earlier?  

Ans 1: In asexual reproduction, the reproducing cells produces a copy of their DNA through some special chemical reactions. However, this copying of DNA is not completely accurate and therefore, the newly  formed DNA has some variations.  


It can be easily seen in the above figure that in asexual reproduction, very few  variations are allowed. Therefore, if a trait is present in only 10% of the total population, it is more likely that the trait has arisen recently. Hence, it can be concluded that trait B that  exists in 60% of the same population has arisen earlier than trait A.  

Ques 2: How does the creation of variations in a species promote survival?  

Ans 2: Sometimes for a species, the environmental conditions change so drastically(badly) so that their  survival becomes difficult. For example, if the temperature of water increases suddenly very high,  most of the bacteria living in that water would die. Only few variants resistant to heat  would be able to survive. If these variants were not there, then the entire species of  bacteria would have been destroyed and become extinct. Thus, these variants help in the survival of the species.  

However, not all variations are useful. Therefore, these are not necessarily beneficial for the individual organisms.















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