、。
I heard he went to America to study biology.
Literal
According-to-what-was-heard, he [topic-は] biology [object-を] study [purpose-ために] went-to-America [hearsay-そうだ].
聞いたところでは is a variant of 聞いたところによると. 渡米する means 'to go to America' — a compact Sino-Japanese verb (渡 = cross + 米 = America). ~ために marks purpose: 'in order to study.' ~そうだ marks the whole statement as hearsay.