Android and iOS continued to gain market share at the expense of struggling platforms like BlackBerry and Windows Phone 7 (WP7), according to a new report from NPD Group.

Android’s share of smartphone sales grew to 53 percent of the U.S. smartphone market (53 percent) from January through October 2011, while Apple’s iOS share grew to 29 percent of the market.

Research In Motion’s OS share declined to 11 percent. RIM and other companies that were formerly on top of NPD’s smartphone rankings, however, have made critical business decisions this past year in a quest to shore up their U.S. smartphone businesses.

Ross Rubin, executive director of connected intelligence for NPD Group, said the impact of Apple and Google on the smartphone market cannot be underestimated.

“The competitive landscape for smartphones, which has been reshaped by Apple and Google, has ultimately forced every major handset provider through a major transition,” Rubin said. “For many of them, 2012 will be a critical year in assessing how effective their responses have been.”

Motorola is a prime example of the volatility inherent in the smartphone market. Motorola took a 36 percent share of smartphone sales in the fourth of 2006. And yet the company’s smartphone market share dropped as low as 1 percent by Q3 2009. However, after adopting Android, Motorola’s share of smartphone sales rose to 16 percent of the market in Q4 2010 before settling back down to 12 percent by Q3 2011.

“Android has helped Motorola climb back into the smartphone market; now, though, Google will seek to use Motorola’s patent pool to help protect other Android licensees,” Rubin said.

RIM has also felt the effects of Android and Apple’s influence over the years. In the second quarter of 2006, RIM comprised half of all smartphone sales. By the third quarter of 2011, the company had fallen to 8 percent. RIM is now ranked fifth among smartphone OEMs, behind Apple, HTC, Samsung and Motorola. The company is hoping it’s on the rebound with the impending launch of its QNX-based BlackBerry 10 operating system.

Microsoft too has seen Windows Mobile, which once controlled 50 percent of smartphone sales in 2007, get demolished by the competition. WP7 currently holds just under 2 percent of smartphone sales since the new platform launched in the fourth quarter of 2010.