[eli5] Why do insects have lots of legs while larger animals have 4 or 2? Also, why aren’t there any animals (that I know of) with 3 legs?
In: 381
the number of legs an animal has depends on its evolutionary history and adaptations to specific ecological niches. Considering Insects have six legs because they evolved from an ancestral lineage that had three pairs of legs. Over time, these legs became specialized for different functions such as walking, grasping, jumping, and swimming. The presence of six legs allows insects to move efficiently in the complex microenvironments they inhabit, such as dense vegetation, soil, and water.
While larger animals with four legs (quadrupeds) and two legs (bipedal) also evolved from different lineages with different ecological pressures. Quadrupeds evolved from terrestrial ancestors that needed to move on land without sinking in, and four legs provided a stable foundation for this movement. Bipedal animals, such as humans and birds, evolved from quadrupedal ancestors and gained an advantage in running and jumping.
As for the absence of three-legged animals, it may be due to the nature selection theory that support the advantages of bilateral symmetry. Most animals have a left and a right side that are nearly mirror images of each other. Three legs would break this symmetry, potentially leading to imbalanced movements or a disadvantage during “Locomotion” which easily lead them to face the hardship in striving for food and survival as well as escaping from the dangers
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