The differences from the average of the traits as found in various individuals of a species are called variations. What does "average of the traits" mean?
I got this definition of variation in a book. Please elaborate on the meaning of average of the traits in it.
The concept that is being referred to is known as heritability. This describes how much genetics plays a role in the differences(variations) in a population. An example could be height. People have a great variation in their height. Heritability which is often studied in quantitative genetics attempts to learn the relative contributions of genetic and non-genetic differences in the phenotypic variation of a population. In other words, if we observe height, how much is due to genetics, how much is due to the environment to account for the different phenotypes among people.