Which of the following steps of meiosis contribute to genetic variation

Crossing over during meiosis is responsible for the occurance of genetic variation in living organisms.

Explanation:

Crossing over occurs in the meiosis in which parts of chromosomes are exchanged between two different chromatids which causes variation in the organisms. This occurs between two non sister homologous chromosomes. Due to crossing over, organisms that are produced is different from their parents.

it restores trees to areas where they once grew.

organ system-an organ system is a group of organs that work together to perform one or more functions. each does a particular job in the body, and is made up of certain tissues.