Analyse of Vertebrate Forelimbs

Topics: Cetacea, Whale, Species Pages: 4 (1255 words) Published: April 2, 2006
1.Gather information from secondary sources (including photos/diagrams/models) to observe, analyse and compare the structure of vertebrate forelimbs.

Comparative anatomy is the study of the differences and similarities in structure between different organisms. An example of comparative anatomy is the pentadactyl limb which is the basic five-digit bone structure of many vertebrate's forelimbs. The vertebrate forelimb (or the pentadactyl limb) comprises of the humerus (upper arm), radius and ulna (forearm), carpals (wrist), metacarpals (palm of hand), and phalanges (fingers).

The pentadactyl limb is evidence that present-day vertebrates (which include fish, birds, amphibians, reptiles and mammals) are closely related. It is believed they inherited this structure from an ancient aquatic ancestor, the lobe-finned fish. Due to natural selection, all vertebrate forelimbs, although have the same structure, are modified for very different uses. Therefore vertebrate forelimbs are homologous structures. Homologous structures are structures in different species that are similar because of common ancestry. They have the same basic structure but may appear somewhat different depending on the degree of modification produced by evolution.

One use for the vertebrate forelimb is swimming. Whales, otters and penguins have forelimbs which are modified to allow them to swim efficiently. The bones in whales are relatively compact and do not move within the flipper. This provides them with a strong ‘paddle' which allows the whale to control the direction of their swimming. However, Otters have more flexible arms which allow for more movement. The metacarpals and phalanges are connected by skin which provides a webbed appearance. Penguins bone arrangement is only slightly different from a whale, although penguins are birds and their forelimbs were first adapted for flight and then swimming. Running is...
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