9:31 how do you know that it’s 40% is due to genetic differences and not due to environmental source? Is it possible that this could be other way around or does environmental source always have a bigger proportion?
In this video, I provided an example that if you get heritability estimate 0.4, it means that 40% of the variation in birth weights of animals is due to genetic differences and the remaining 60% part of the phenotypic variance is due to the environmental differences. Normally, the estimate of heritability varies from one population to another population. For instance, at one farm you can obtain heritability as 0.2 and on another farm it might be 0.3 or 0.05 etc. So, it's possible that you can get a different value of heritability for the birth weights of the same cattle breed raised in a different location or in a different production system. Heritability gives us information on how much of the phenotypic variance is due to genetic differences among individuals in a population. You can get higher or lower estimates of heritability for a trait even for the same population because it depends on different things like what method you use to estimate it and how many no. of records you have etc. Similarly, it's not always true that environmental sources have a higher part in causing variation in a trait. For some traits, the heritability might be higher like 0.6 or 0.7, so in this case the major part of phenotypic variance would be due to the genetic differences among individuals of a population.
