Final answer:
Crossing over in meiosis results in the production of new combinations of genes, increasing genetic diversity and facilitating natural selection under changed environment.
Step-by-step explanation:
Crossing over in meiosis results in the production of new combinations of genes, which can be advantageous for natural selection in a changed environment. This process increases genetic diversity and allows offspring to possess new traits that can help them survive during environmental changes. For example, if there is a change in the availability of resources, offspring with different genotypes resulting from crossing over may have better adaptations and higher chances of survival. Therefore, crossing over plays a crucial role in increasing genetic variation and facilitating natural selection.