Final answer:
Haplorrhines present a greater anatomical variation compared to strepsirrhines because they have evolved to adapt to diverse environments and have a range of physical traits that support both arboreal and terrestrial lifestyles.
Step-by-step explanation:
The anatomy of haplorrhines is more varied than that of strepsirrhines due to several factors. Haplorrhines include the infraorders Simiiformes and Tarsiiformes, encompassing New World monkeys, Old World monkeys, apes, humans, and tarsiers. Their adaptations allow them a diurnal lifestyle and a greater reliance on vision rather than smell, which is a contrast to the more olfactory-focused, nocturnal strepsirrhines such as lemurs and lorises.
The Simiiformes are divided into Platyrrhini (New World monkeys) and Catarrhini (Old World monkeys and apes including humans). New World monkeys boast prehensile tails used for arboreal navigation, whereas the Catarrhini, including the Cercopithecoidea (cheek pouch and leaf-eating monkeys) and the Hominoidea (apes and humans), have narrow nostrils facing downward, larger brains, and, in many species, increased ground-dwelling tendencies.
These anatomical and physiological traits reflect the diverse environments and lifestyles haplorrhines have adapted to, resulting in a greater variation in their physical forms when compared to the more primitive strepsirrhines.