Isaac Asimov attributes the science verse to some nameless MIT student.
In Isaac Asimov's Treasury of Humor, page 184, he
says he heard it at an MIT Science Fiction Club annual picknik.

Last line slightly different from the one posted above.

Nuclear fusion makes stars to shine,
Tropisms make the ivy twine,
Raleigh scattering make skies so blue,
Testicular hormones are why I love you.