Thursday, March 24, 2011
A Right to Arms
In class earlier this semester, we discussed the evolutionary history of vertebrates. On page 26 of Your Inner Fish there is a diagram described as "Tracing arm bones from fish to humans." Describe the similarities of arm bones in vertebrates providing references from both Shubin, Cambell, and any outside sources. Further discuss the similarities we see among the vertebrates and describe the distinguishing features among the vertebrates. Reference the vertebrate morphological and molecular trees in your response.
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ReplyDeleteOn page 31, Shubin provides a diagram of many different vertebrate arm bones. He states that all limbs have "One bone, followed by two bones, then little blobs, then fingers or toes". He further states that all vertebrate arm bones can be made with this model by morphing sizes and shapes. Even bat wings, frog arms, and fish fins can be made using this model, which shows that all vertebrates come from a common ancestor, since all vertebrates have this common feature.
ReplyDeleteVertebrates all come from a common deuterostome. This common deuterostome gave way to the common ancestor of all chordates, which had a notochord. Other common chordate features include a muscular, post-anal tail, a dorsal, hollow nerve cord, and pharyngeal slits or clefts (Campbell 699). Hagfishes were the first chordates to have increased cephalization, but the first true vertebrates were the lampreys, because they had a vertebral column. All vertebrates have neural crest cells, increased cephalization, a vertebral column, and a closed circulatory system, for efficiency in energy transfer (Campbell 704). This is probably what allowed vertebrates to start on a path of success from water to land. As the vertebrates further evolved from lampreys, they developed jaws, lungs, lobed fins, and, eventually, legs to walk on land. Once class Reptilia emerges, amniotic eggs are present, and with mammals, milk is developed. These evolutionary advances enabled vertebrates to have powered flight, unique among vertebrates and insects, and an increased ability of mobility, efficiency, and the ability to survive and reproduce (Nelson 1). Vertebrates were also among some of the first creatures to exhibit advanced forms of learning, like associative learning, and being able to exhibit classical conditioning (Nelson 3).
http://www.ucmp.berkeley.edu/vertebrates/vertsy.html