It （主语）//is（系动词） something（表语）// close to what parts of biological brains can do（后置定语）. 

解答：句子中的close 形容词意思为“近的;接近的，酷似的”

close to 离…近; 与…关系密切; 近乎; 临近

Three mortar shells had landed close to a crowd of people.  

3枚迫击炮弹落在人群旁。

Warm weather has attracted the flat fish close to shore.  

煦暖的气候将比目鱼引到了近海。

An airliner came close to disaster while approaching Heathrow Airport. 

一架大型客机在飞近希思罗机场时差点儿发生空难。

For my part, I feel elated and close to tears.  

就我而言，我感到非常高兴，都快落泪了。

Animal welfare is a subject very close to my heart.  

动物福利是我非常关注的一个问题。

Gunfire was heard at an army base close to the airport.  

机场附近的军事基地传出了炮火声。