Living things vary tremendously in their characteristic body size. The range of mass spans more than 21 orders of magnitude, from the smallest known organisms (myco-plasm) at ^10~13g to the largest (blue whale) at 10 g (180-200 t). Even insects, a group typically thought of as relatively diminutive, have body sizes ranging over more than three orders of magnitude (Table 1). This includes feather-winged beetles, which readily could move through the eye of a needle, and the Goliath beetle from Africa, which is bigger than a typical dinner plate. The body mass span is extended considerably if one considers extinct insect species such as Meganeura with wingspans of ^70 cm. For centuries, biologists have been interested in what underlies this incredible diversity; why organisms evolve a certain size; and what the ecological and evolutionary consequences and tradeoffs are of each.
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