Accumulation of Variation During Reproduction
Heredity can be defined as resemblances among individuals related by descent or the transmission of traits from parents to the offspring. It means continuity of features from one generation to the next. Variation is defined as the occurrence of differences in the characters (or traits) among the individuals. In a number of sexually reproducing animals, including human beings, quite distinct variations are visible among different individuals. The long term accumulation of variations may lead to gradual changes in the form or functions of organisms and may even lead to the formation of a new species over time. This process is known as evolution.
In case an organism reproduces by asexual reproduction, one organism gives rise to two individuals which are similar in body design, but having subtle differences. These will in turn give rise to two individuals in the next generation. In this way, the four individuals formed will be different from each other.
If sexual reproduction is involved, greater diversity will be generated in the offspring as compared to asexual reproduction where only minor differences would be generated due to small inaccuracies in DNA copying. Depending on the nature of variations, different individuals would have different kinds of advantages. The Selection of variants by environmental factors forms the basis for evolutionary processes.
Example 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?
Answer:
Trait B is likely to have arisen earlier as trait B exists in 60 % of the population as compared to trait A which exists in 10% of the population. Organisms with trait B reproduced and replicated the trait for a longer period as compared to trait A.