Chloroplasts because that is the substance that gives leaves its green colour and also helps in photosynthesis
Inheritance is the process by which traits are passed from the parents to their offspring. The basic unit of inheritance in human is the DNA. For traits to be passed from the parent to the offspring, the DNA in the cell must be duplicated and this happens through the process of cellular reproduction.
The oldest layers are on the bottom thats why they are the oldest. Super position is what it is called if thats what your asking.