A symbiotic relationship refers to an interaction between the two organisms in which both the organism gets to benefit from each other. The symbiotic relationship after some time becomes permanent and both the organism become dependent on each other that both are unable to survive without each other.
In the given question, the microbes growing in the digestive system helps us digest food as they use the complex component of food which is not easily digested by the system, therefore, the microbes gets the nutrients and the system is able to digest the complex biomolecules.
During crossing over, part of one chromosome is exchanged with another. The result is a hybrid chromosome with a unique pattern of genetic material. Gametes gain the ability to be genetically different from their neighboring gametes after crossing over occurs.
