The number one bus pulls up to the curb next to Johnston Gate and Mass Hall, and with a wheeze, opens its doors to allow passengers aboard.

Twenty-five minutes later; the manicured lawns and cobblestone streets are gone as the bus pulls into Dudley Square, the hub of one of Boston's poorest neighborhoods.

As the number one winds its way from Harvard Square to MIT, across the Charles, through the Back Bay, by the Boston Medical Center before finally stopping at Dudley Station, the MTBA bus cuts through more than just the city of Boston; it cuts through the region's full spectrum of social, racial and intellectual diversity.

First Stop: Harvard Square

At the Harvard Square stop on a recent weekday afternoon, the number one has several empty blue vinyl seats.

Three teenage girls are in the front, talking quietly. Two more teenagers laugh and chatter in the back. Other than these sounds, the bus is quiet.

A middle-aged man who doesn't give his name says there is a simple difference between this stop and the one at the end of the ride.

"In Harvard Square, you've got a university. In Dudley, you don't," he says.

"I live near Dudley, and I work in Harvard Square, so they're the same to me," he says.

Second Stop: Central

The bus follows Mass. Ave. and stops near Cambridge City Hall.

Carrying several overflowing bags, Maura E. Murphy steps on and stumbles into a seat.

"It's crowded in the rush hour," she says, nodding to the empty front of the bus.

Murphy takes the bus nearly every day from Central to homeless shelters in Boston, and frequently visits both Harvard Square and Dudley Square.

She says the population and the buildings differ.