Answer:
Variation within genes leads to different genotypes , which can be seen by the individuals having different phenotypes . For example, the dogs above all have different fur colours and fur lengths. Genetic and environmental variation combine together to produce these different phenotypes.
It is something that has been proven and has had the same result for multiple years
Answer: Formation of precipitate indicates that there has been a chemical reaction.
Explanation:
Chemical reaction: It is defined as change in arrangement of the atoms so as to form a new substance.
Mixing of two clear solutions that is lead nitrate and potassium iodide gives out yellow solid precipitate of lead iodide with aqueous solution of potassium nitrate.

The physical evidence which indicates that chemical reaction has been taken place is formation of yellow solid precipitate of lead iodide ,(
).