The correct answer is B) Environmental factors can determine if a genetic trait becomes a health issue.
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The statement above is false. The blood levels of calcium is regulated by parathyroid hormone.When one is not getting adequate calcium in one's diet and the blood level of calcium is low, the parathyroid hormone will be released. The parathyroid hormone can increase the blood calcium in several ways:
1. by stimulating osteoclasts which break down bone and release calcium into the blood stream.
2. by increasing the amount of calcium re-absorbed by the kidney before it can be excreted in urine.
3. by triggering the formation of calcitriol which increases the absorption of dietary calcium at the intestines.
• Homologous structures: Both Ostriches have wings similar in form to those of their ancestors, but that do not allow the birds to fly.
Homologous structures are those that have structural similarities but are different in function. For example, if we look at the anatomical structure of a bird’s wing, it is very similar in structure with a human arm. However, over the course of time they have evolved to perform different functions.
• Vestigial structures: The inner ear bones of mammals have evolved from bones that form the jaws of reptiles.
Vestigiality refers to the process in which some structure lose their function over the course of evolution in some specie but they are functionally normal in other species. Such a structure is the inner ear bones of mammals which donot perform an important function in mammals but do perform in reptiles.
• DNA sequence data: Both Genes involved in RNA replication are conserved among bacteria and animals, suggesting a common evolutionary origin.
The sequencing of genetic data is an excellent method of finding the evolutionary histories and relatedness of different organisms. This field of sciences is called phylogenetics and the mentioned example is the result of phylogenetics.
• Analogous structures: The jointed legs of insects and vertebrates arose independently, indicating a different evolutionary origin.
Analogous structures are those that have similar function but they look very different in structure or anatomy. This is because they have been evolved from different ancestors and perform different functions. One example of these structures is mentioned, The jointed legs of insects and vertebrates that look different bur perform same function.
