TOEFL iBT Speaking. In this integrated speaking task, you will listen to part of

Listen to part of a lecture in a biology class.
Birds have many physical features that contribute to their flying ability. Wings are important, but so are adjustable tails, strong muscles, large hearts, and light bones.
A bird’s wings are designed so air above the wing is forced to move faster than air below the wing. This creates higher pressure under the wings, called lift, which pushes the bird up. Different wing types evolved for different ways of flying. Birds that fly long distances need long wings and the ability to soar. Other birds need superior maneuverability. Fast birds, like hawks and falcons, have wings with built-in spoilers that reduce turbulence during a speedy flight.
A bird’s tail acts like a rudder to help the bird steer. Birds brake by spreading out their tails as they land. This adjustment allows them to make sudden, controlled stops—an essential skill, since most birds need to land on tree branches, or on the prey that will be their dinner.
Flapping the wings to take off requires muscle strength, and strong muscles need oxygen. Birds have large, specialized hearts that beat much faster than the human heart and provide the necessary oxygen to the breast muscles. A bird’s breast muscle accounts for 15 percent of its body weight. On some birds, such as pigeons, the breast muscle accounts for one-third of their total body weight.
Birds carry no excess baggage. They have hollow feathers and hollow bones. The bones have struts inside them, like the crossbeams in a bridge, which gives them strength without adding much weight.
Using points and examples from the lecture, explain how a bird’s physical features contribute to its ability to fly.