Final answer:
James Madison advocated for a bicameral legislature apportioned by population under the Virginia Plan, which was later modified by the Connecticut Compromise for population-based representation in the House and equal representation in the Senate.
Step-by-step explanation:
James Madison and the Bicameral Legislature
James Madison advocated for a bicameral legislature that would be apportioned by population. Madison's Virginia Plan proposed a two-house Congress, with representation in both houses determined proportionally by each state's population, giving more populous states like Virginia more political influence. Eventually, the Connecticut Compromise was reached which maintained a bicameral Congress but differed in the method of apportionment between the two houses: equal representation in the Senate and population-based representation in the House of Representatives.