In the new series “Human: The World Within” (PBS, 9 p.m., check local listings) looks at biological stories from around the world to illustrate birth, in the first hour, and the heart and circulatory system in the second. 

A journalist convinced that New York killer Son of Sam did not work alone in the late 1970s, explains the theory in the new documentary series “The Sons of Sam: A Descent into Darkness” (Netflix, streaming). 

“The Circle” (Netflix, streaming) ends its second U.S. season by naming a $100,000 winner.

Tiffany Haddish hoses a new season of “Kids Say the Darndest Things” (CBS, 8 p.m.), but on a new network. It was on ABC for its 2019-20 season. Networks do the darnedest things. 

Chrissy Metz is guest panelist on “The Masked Singer” (Fox, 8 p.m.), where the final six perform. 

“Chicago Med” (NBC, 8 p.m.) deals with an auto accident; “Chicago Fire” (NBC, 9 p.m.) gets a mysterious call; and “Chicago P.D.” (NBC, 10 p.m.) deals with the murder of a pregnant woman. 

Tom vows to help more around the house on “Home Economics” (ABC, 8:30 p.m.).

“SEAL Team” (CBS, 9 p.m.) brings a defecting Book Haram lieutenant into U.S. custody.