Final answer:
Gibbons and Siamangs are arboreal lesser apes with low sexual dimorphism and long arms for brachiation. Siamangs are larger and have a vocal sac for amplification of calls. Great apes show higher sexual dimorphism, varied social structures, and diverse diets, with humans being most closely related to chimpanzees and bonobos.
Step-by-step explanation:
The characteristics of Gibbons and Siamangs, which are lesser apes, mainly revolve around their arboreal lifestyle and physical adaptations to their environment. Gibbons are known for their incredibly long arms, which they use for a form of locomotion known as brachiation, swinging from tree limb to tree limb with ease. They exhibit low sexual dimorphism, meaning there isn't a significant size difference between males and females. However, some gibbon species display color differences between sexes. Siamangs, a larger type of gibbon, share many characteristics with other gibbons but are notable for their larger size and the distinct vocal sac they use to amplify their calls through the forest. Both gibbons and siamangs live in the tropical and subtropical regions of Asia and have a diet that typically consists of fruits, leaves, and sometimes insects. Comparatively, great apes like orangutans, gorillas, and chimpanzees, which includes the closely related bonobos, are larger and exhibit higher levels of sexual dimorphism, especially in gorillas where males are about twice the size of females. Orangutans are solitary and mostly arboreal, gorillas are ground-dwelling and live in social groups, while chimpanzees and bonobos are known for their complex social structures and behaviors. Bonobos tend to be less aggressive than chimpanzees and retain juvenile features such as white tail tufts for life. The dietary habits of these apes vary, with orangutans favoring fruits and gorillas preferring foliage.