There is less energy available to consumers at higher levels in a food chain. Why?

Energy decreases as it moves up trophic levels because energy is lost as metabolic heat when the organisms from one trophic level are consumed by organisms from the next level.

Explanation:

While scientists have known of DNA's existence for much longer, until 1985 they didn't know that the DNA of each person differed - FALSE

This statement is false.

The DNA was discovered decades before 1950's and its structure was concluded by James Watson and Francis Crick in 1953. Hence by 1985 scientists knew that each person's DNA differ.