Answer:
The constitutional principle that the 2010 Census scenario with gained and lost seats illustrates is called reapportionment. It is explained in Article Two of the US Constitution.
Explanation:
The number of representatives for each state in the House of Representatives is decided based on population numbers recorded in the Census and then the seats are proportionally distributed between each state, with the number of seats always totaling 435. It is also written in Article One of the Constitution that each state should have at least 1 seat, in the case where a state's population might fall below the threshold in proportion to other states. Due to the 2010 Census states, in the South and West tended to gain seats with reapportionment while those in the Great Lakes region especially lost seats. The evidence of reapportionment is described very clearly in Article Two of the Constitution.