Joints, or articulations, exist wherever two bones meet. The function of each joint is closely related to its structure. Each joint reflects a workable compromise between the need for strength and the need for mobility. When movement is not required, joints can be very strong. For example, joints such as the sutures of the skull lock its separate elements together as if they were a single bone. At other joints, movement is more important than strength. At highly mobile joints, the interconnections between bones are looser and the joints weaker. For example, the shoulder joint permits a great variety of arm movements. The range of motion is limited more by the surrounding muscles than by joint structure. The joint itself is relatively weak, however, and shoulder injuries are rather common.
a. example and explanation
b. definition and explanation c. example and enumeration
Question 2
Two closely related species of animals may overlap in their ranges and yet feed, mate, and grow in separate areas, which are called habitats. If they use different habitats, this means they may rarely meet up. If so, gene flow will be greatly restricted between them. Lions and tigers can interbreed, but they never have in nature, even when their ranges overlapped in the past. One reason for this is their largely separate habitats: Lions prefer the open grasslands, tigers the deep forests.
The purpose of the paragraph is
a. to compare the habitats of the lion and the tiger.
b. to inform the reader that closely related species of animals do not
interbreed, mostly because of different habitats.
c. to inform the reader that lions and tigers could never interbreed
regardless of habitats.
The tone of the paragraph is
a. informative. b. defensive. c. argumentative.
Examples of structures in which extensive surface area is important for function.
hip bones
Bones Markings
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