SCIENCE CONCEPT: Bat and bird wings have similarities and differences. In looking at the platform of the wings of various bats we can compare with the similar wing platforms among birds. Based on the wing platform, what can we say about the bat flight characteristics in contrast to the bird's flight characteristics. STUDENT OBJECTIVE: The student will observe through pictures how the platform of the wings of bats and birds have similarities and differences. Because of the shape of the wings, the bat and the bird have certain flight characteristics. OVERVIEW: In this activity, the student will view several pictures of bats and birds, particularly studying the platform of the wings of both. After discussion with other classmates the students will make wings out of origami paper and straws of a megabat, a microbat, and a bird. There are two major bat divisions within the animal order, chiroptera. They are microbats and megabats. We will focus on the overview of the two groups and not particular species within either group.

PREPARATION TIME: 20 minutes. LESSON TIME: 30 minutes. TEACHER PREP: Gather pictures of megabats, microbats, and birds showing their wing spans. WORDS TO KNOW: taut membrane platform leading edge airfoil megabats microbats

Although bats can fly like a bird, they do not have feathers, build nests, or lay eggs. Bats are mammals. Their bodies are covered with fur and they are born live. As babies they are fed milk by their mothers. Bats are expert fliers. Although a bat's body is adapted to flight (the neck is short, the chest is massive with powerfully developed muscles, and the abdomen is narrow and tapering), in order to fly a body must have a wide, thin surface (airfoil) and the power to push it through the air (propulsion). In a bat, it is the wings that are both the airfoil and the propulsion system. Among vertebrates, bats, as well as birds, have been able to conquer the skies in active flight because of their wings.

A bat's wing consists of bones that are very similar to the bones in a human arm and hand. Long arm bones, with extra-long extended finger bones, are covered with a double layer of thin skin called a membrane. The membrane, which looks similar to the skin between the toes of a duck's foot, is so thin you can see light through it. It is made up of fine blood vessels, elastic fibers and muscle fibers. The fibers help keep the flight membrane taut and aid in folding of the wing membrane when the bat is at rest. The second and third fingers, along with the membrane in between, give the wing a stiff leading edge similar to an airplane's, while the third finger forms the wing tip.

Bats fly through the air in a rowing motion. On the downstroke, the wing moves backwards and upwards. Then the wings are swung outwards and downwards. Finally, they are drawn forward with the tips drawn almost together in front of the head forming the shape of an open umbrella. On the upstroke the wings are moved first upwards and then backwards. Similar to birds, strong, large muscles provide powerful wing strokes that enable flight. While birds use the strong muscles fastened to their large breastbone, bats move their wings by using the large muscles in their backs and chests. Some of these muscles pull the wing up, while others bring them down.

Although birds use their tails to brake and steer, bats use their wings by folding one wing for a second and using one independently of the other. Many bats have also mastered hovering flight, similar to hummingbirds and helicopters, that enables them to remain stationery in flight, while other bats are able to achieve brief periods of gliding flight.

The wing area of microbats is smaller than their body size. These insect eating bats must make up for their small wing size by increasing their number of wing strokes. They raise and lower their wings from 11-18 times per second. These small, fast moving wings enable microbats to change direction quickly and sometimes even hover in flight while hunting.

The megabats are larger bats with simple ears and large, dog-like eyes. The wing area of these fruit eating megabats is larger than their body size. Wings often reach spans of 2 meters with wing beats of as few as 7 per second. Due to the air resistance on its large wings, megabats appear to be slow and ponderous in flight. But with long narrow wings, it is not unusual for megabats to travel 50-80 km in one night to feed.

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