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Prions are proteins that act as an infectious agent. They cause a variety of diseases, including “Mad Cow” disease. Prions cannot produce more prions on their own, but cause the host organism to replicate more prions. Most scientists do not consider prions to be alive. A valid reason for accepting that prions are nonliving things is that*
The diagram below represents an incomplete sequence of levels of organization.
organelles → tissues → organs → organ systems → organism
This sequence can be completed correctly by inserting*
Which sequence best represents increasing complexity?*
Rabbits have evolved strategies that get them through periods of time when there is little food. The diagram below represents essential life functions that rabbits need to perform.
Which life function in the diagram could be eliminated without affecting an individual rabbit’s ability to survive when food is scarce?*
Bacteria and humans are similar in that they both*
During gas exchange, the cell membrane of a single-celled organism has the same function as which organ system in humans?*
Which sequence represents structures organized from least complex to most complex?*
Scientists who study rock formations in caves describe some of the formations as “living rock” because, under certain conditions, they increase in size. Which statement would best dispute the claim that these rock formations are living?*
Fish absorb oxygen through the gills, earth- worms absorb oxygen through the skin, amebas take in oxygen through the cell membranes, and cows inhale oxygen through the nasal passages into their lungs. This statement demonstrates that living things*
Which diagram best illustrates the relationship between the number of cells, tissues, and organs in a complex multicellular organism?*
Base your answers to questions 11 on the diagrams below and on your knowledge of biology. The diagrams represent a single-celled organism and a multicellular organism.
Which statement correctly identifies the levels of organization for the structures indicated?*
The sequence below represents different organizational levels within the human body, from the simplest to more complex. Complete the sequence by correctly filling in the missing levels. 
organelles → ________________ → tissues → ________________ → organ systems → organism*
Select one row in the chart below and explain how the systems in that row work together during exercise. 
Base your answer to question 14-17 on the information below and on your knowledge of biology.
It is estimated that every year more than 15 million babies are born too early. The lungs of these premature infants are often immature and easily damaged. Premature births happen for a variety of reasons—some known and some unknown. Those that are known include infections and conditions such as diabetes and high blood pressure. Scientists are researching what causes premature births, in an attempt to develop solutions to prevent them.
Scientists are also working on the development of an artificial placenta. At the University of Michigan, five premature lambs were placed in artificial placentas and kept alive for weeks. During this time, each lamb’s blood was circulated through its artificial placenta.
Discuss how the development of an artificial placenta is an important step in the study of premature births. In your answer, be sure to:
• explain why it would be harmful for a human mother’s blood to pass across the placenta and into the
• state how an artificial placenta would be of benefit to the lungs of premature infants 
• explain why the lambs’ blood must be filtered as it circulates through the artificial placenta 
• state one reason why premature lambs were likely used as model organisms in this study rather than
Base your answers to questions 18 on the information below and on your knowledge of biology.
Mitochondrial Replacement Therapy
Mutations in mitochondrial DNA (mtDNA) are associated with some severe human diseases and are inherited through the cytoplasm in the egg cell. These diseases vary, but often affect organs and tissues with the highest energy requirements, including the brain, heart, muscle, pancreas, and kidney.
Scientists have successfully used mitochondrial replacement therapy with monkeys. Scientists are considering using this technique to reduce the incidence of mitochondrial disease in children. The proposed treatment would involve removing the nucleus from an egg donated by a healthy woman and replacing it with an egg nucleus from a patient (mother) with mitochondrial disease. This would place the patient’s egg nucleus into the cytoplasm of the donor’s egg containing healthy mitochondria. The egg is then fertilized with the father’s sperm externally using in vitro fertilization (IVF) to produce a zygote. The zygote is cultured for a few days to produce an embryo.
State one reason why muscle tissues are likely to be affected by mitochondrial diseases. *