Meselson and Stahl designed an experiment that would allow them to discern whether DNA replication occurs in a dispersive, semi conservative, or conservative manner. They started with E. coli that had been growing for many generations in medium containing 15N. They then transferred the bacteria into medium containing only 14N, and allowed the bacteria to undergo two rounds of DNA replication. After each round of replication, the scientists performed density-gradient centrifugation of the DNA. The scientists reasoned that each of the three models would predict different DNA banding patterns after the two rounds of replication. Can you identify the banding patterns predicted by each model after the first round of replication? Drag the test tubes to the appropriate locations in the table to show the banding patterns that each model predicts. Test tubes may be used once, more than once, or not at all.

The diagram below represents a marine food web and a process that can harm the human population. each circle represents an organism and the smaller dots inside them represent a toxic substance. what is being represented and how does it harm the population? the diagram represents biological half-life, in which toxins build up in organisms higher up on the food chain, and this can negatively impact humans who consume the organisms and the toxic substance. the diagram represents biomagnification, in which toxins build up in organisms higher up on the food chain, and this can negatively impact humans who consume the organisms and the toxic substance. the diagram represents the process by which different organisms prey upon each other; this can impact the human population by reducing the number of organisms that do not contain the toxin. the diagram represents the way that toxins are metabolized by living organisms, with those at greater trophic levels able to metabolize more efficiently than those at lower levels. this means that those at higher tropic levels are safer for humans to consume compared to the organisms at lower trophic levels.

Describe the response the kidneys have to dehydration and excessive water intake. what happens to the concentration of urine in each case ?

Which two factors contributed to creating a global culture? the creation of the united nations improvement in telecommunications health issues such as the ebola virus increased opportunities for global travel