Chana

The United Nations estimates that in one week, on October 31, 2011, the world's population will reach 7 billion. Just 200 years ago, there were only 1 billion people on the planet, and over the next 150 years, that number grew to 3 billion. But in the past 50 years, the world's population has more than doubled, and it is projected to grow to 15 billion by the year 2100. As the UN points out, this increasing rate of change brings with it enormous challenges. Meeting the basic needs of so many will meaning growing, shipping, and distributing more food while providing more clean water, health care, and shelter -- all without inflicting too much further damage on our environment. [42 photos]

A baby gestures minutes after he was born inside the pediatric unit at hospital Escuela in Tegucigalpa, Honduras, on October 21, 2011. According to Honduras' health authorities, about 220,000 babies are born in Honduras each year and the cost of having a baby delivered at the public hospital is $10. (Reuters/Edgard Garrido)