Most organisms are Diploid, and as a result, they will have received 2 copies of the chromosomes, or sets of chromosomes, from both their parents. This they will have 2 sets of Genes that will perform almost exact same process, except with different phenotypes.
These chromosomes need to be homologous, in order for new alleles and other genetic combinations to be made.
Because you might have just done something different with the experiment and messed up someway during the test
Well, rabbits would eat all of the vegetation leaving other animals without food.
