Did you know that sloths are able to spend most of their time hanging upside down from tree branches because their internal organs are attached to their rib cages to keep them from weighing down their lungs, permitting them to breathe easily? Anyway, here are this weekend's subway changes.

South Ferry-bound 1 trains will make express stops from 34 St-Penn Station to Chambers St from 11:45 p.m. Friday to 5 a.m. Monday.

Flatbush Av-Brooklyn College bound 2 trains will make express stops from 34 St-Penn Station to Chambers St from 11:45 p.m. Friday to 6:30 a.m. Sunday, and again from 11:45 p.m. Sunday to 5 a.m. Monday. Also on that track, trains will run express from Atlantic Av-Barclays Ctr to Franklin Av. from 11:45 p.m. Friday to 5 a.m. Monday.

3 trains will operate to/from New Lots Av from 11:45 p.m. Friday to 5 a.m. Monday. Trains on the New Lots Av-bound track will run express from Atlantic Av-Barclays Ctr to Franklin Av from 11:45 p.m. Friday to 5 a.m. Monday.

All 4 trains will make local stops from 125 St to Brooklyn Bridge-City Hall from 11:45 p.m. Friday to 5 a.m. Monday. Trains will not run at all between New Lots Av/Utica Av and Brooklyn Bridge-City Hall during that time. On the Woodlawn-bound track, trains will run express from 149 St-Grand Concourse to Burnside Av from 3:45 a.m. Saturday to 10 p.m. Sunday. All trains will run every 16 minutes between Woodlawn and 125 St, with some Woodlawn-bound trains terminating at 125 St; this change is in effect from 7:30 a.m. to 7 p.m. Saturday, and from 9:30 a.m. to 7 p.m. Sunday.

5 trains will not run at all between Bowling Green and Grand Central-42 St, with that change in effect from 6 a.m. to 11 p.m. Saturday and from 8 a.m. to 11 p.m. Sunday.

Main St-bound 7 trains will run express from Queensboro Plaza to 74 St-Broadway, starting at 3:45 a.m. Saturday and ending at 10 p.m. Sunday.

All A trains will reroute along the F line between W 4 St-Wash Sq and Jay St-MetroTech from 11:45 p.m. Friday to 5 a.m. Monday. Brooklyn-bound A trains will stop at 163 St and 155 St from 12:01 a.m. Saturday to 5 a.m. Monday.

All C trains will reroute along the F line from W 4 St-Wash Sq to Jay St-MetroTech from 6:30 a.m. to midnight on Saturday and Sunday.

World Trade Center-bound E trains will run express from Forest Hills-71 Av to Queens Plaza from 11:45 p.m. Friday to 7 a.m. Sunday, and again from 11:45 p.m. Sunday to 5 a.m. Monday. Trains on that track skip Briarwood and 75 Av from 11:45 p.m. Friday to 5 a.m. Monday.

F trains will not run at all between Coney Island-Stillwell Av and Church Av from 11:45 p.m. Friday to 5 a.m. Monday. Coney Island-Stillwell Av bound trains will skip Sutphin Blvd, Briarwood, and 75 Av from 11:45 p.m. Friday to 5 a.m. Monday, as well as 23 St and 14 St.

L trains will not run at all between 8 Av and 14 St-Union Sq from 11:45 p.m. Friday to 5 a.m. Monday.

Astoria-Ditmars Blvd bound N trains will run express from Queensboro Plaza to Astoria-Blvd, with that change in effect from 6:45 a.m. to 7 p.m. on Friday.

Manhattan-bound R trains run express from 71 Av to Queens Plaza from 6:30 a.m. to midnight on Saturday and Sunday.