In birds, the forearm muscles supinate, pronate, flex and extend the distal wing. Wings. The basic design of the mammalian forelimb demonstrates the evolutionary phenomenon of adaptive radiation. Analogous structures are structures that are similar in unrelated organisms. B. The forelimbs of a human, cat, whale, and bat all have strikingly similar bone structures. Figure \(\PageIndex{1}\): Homology in the forelimbs of vertebrates: The principle of homology illustrated by the adaptive radiation of the forelimb of mammals. Option e (composition) is not correct because the forelimbs of early mammals have the same bone composition. Homology indicates common ancestry. Structures that are embryologically similar, but have different functions, are called homologous structures.They have different appearance, perform different functions but have common origin and same basic pattern.This phenomenon of similarity between organs of different animals having common origin is called Homology. If we go all the way back to the beginning of life, all structures are homologous! D. All of the above are correct. The forelimbs of all mammals have the same basic bone structure. Through natural selection, the form of mammalian forelimbs has been modified during the last 65 million years into many shapes to per-form a variety of functions. In mammals it perhaps reaches its peak and greatest diversity. Monotremes have a sprawling posture, and multiple elements in their pectoral girdles, which are ancestral traits for mammals. By adapting to forest, plains, air, water, and underground, mammals have (b) Organs having same origin but different functions are called homologous organs. For example, whales, bats, Cheetah and human (all mammals) share similarities in the pattern of bones of forelimbs. Thus starting at the body and moving outwards, the forelimbs consist of: Humerus – Upper arm; Ulna + Radius – Fore arm All tetrapod forelimbs are homologous, evolving from the same … The figure above represents forelimbs from mammals that all have different uses depending on the environment in which they live, yet they all have the same basic pattern of bones. C. All organisms, including prokaryotes and eukaryotes, use essentially the same genetic code. This is the last question on my … All conform to the basic pentadactyl pattern but are modified for different usages. The forelimbs of all mammals have the same basic structure, modified for different environments. The forelimbs have one large bone, the humerus, two small bones, the radius and ulna, tiny bones of the wrist called the carpals and then the digits. A. Cilia and flagella in all eukaryotes have the same basic structure. All vertebrate skeletons follow the same basic body plan, the bones of each are considered to be homologous. The structures are similar because they evolved to do the same job, not because they were inherited from a common ancestor. Such is the case of the forelimbs of mammals. However, each of these four species' forelimbs performs a different task. The structure of DNA is the same in all organisms. Option c (number) is incorrect because all early mammals have two forelimbs. Frogs, birds, rabbits and lizards all have differently shaped forelimbs, reflecting their different lifestyles. The forelimbs of all mammals have the same basic bone structure. The structures are similar because they evolved to do the same job, not because they were inherited from a common ancestor. The same bones that construct a bat's wings, which are used for flight, also construct a whale's flippers, which are used for swimming. It remains the same all across the vertebrate classes. They inherited this pattern from a common ancestor. These same bones can even be seen in fossils of the extinct lobe-finned fish, Eusthenopteron. Analogous structures are structures that are similar in unrelated organisms. But those different forelimbs all share the same set of homologous bones — the humerus, the radius, and the ulna. Though the fore and hind limbs are basically the same, they have different names for the various bones.
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