Final answer:
Bird bones have air pockets to reduce their weight which is true. The mass of water displaced by a bird bone in water can be calculated from its submerged weight, and together with the bone's mass, gives us its volume and density. Birds have several other weight-reducing adaptations like single ovaries, no teeth, and a keratin beak.
Step-by-step explanation:
Bird bones do indeed have air pockets to reduce their weight, making it true that these adaptations contribute to an average density less than that of the bones of other animals. This is crucial for flight efficiency.
When an ornithologist measures the mass of a bird bone both in air and submerged underwater, they can calculate the bone's volume and density. The mass of water displaced is equal to the difference between the bone's mass in air and its apparent mass when submerged.
Thus, for a bone weighing 45.0 g in air and 3.60 g in water, the mass of water displaced is 45.0 g - 3.60 g, which equals 41.4 g. To find the volume of the bone, we use the principle that 1 g of water corresponds to a volume of 1 cm3, implying the bone's volume is 41.4 cm3. Finally, the average density of the bone is determined by dividing the mass by the volume, which yields an average density of 45.0 g / 41.4 cm3, or approximately 1.09 g/cm3.
Several other adaptations found in birds include pneumatization of bones, a lack of urinary bladder with the presence of a cloaca, and in females, typically only one functional ovary. Additionally, birds' jaws are lightened by replacing heavy jawbones and teeth with a lightweight keratin beak, and feathers facilitate both flight and insulation.