Why did our founding fathers choose to create a bicameral legislative branch?

There were two plans, the New Jersey Plan and the Virginia Plan. New Jersey had a small population, they wanted to have the same number of representatives per state. Virginia had a large population, they wanted representatives to be based on population. So, the Great Compromise created a bicameral congress. Later on, the slave states wanted to count slaves as a part of their population (more representation). Therefore, the 3/5 Compromise stated that 3/5 of the slaves would be counted as a part of their population.