DeShawn is studying homeostasis and circulation. To organize his findings, he constructs two models of the human heart, veins, and arteries: one to represent a non-smoker, and one that includes attributes typically found in a smoker. By comparing the two models, which relationship of cause and effect can DeShawn best explain? A. Contractions of the heart move blood through the circulatory system.
B. Smoking causes changes to homeostasis throughout the body.
C. Smoking damages the function of the circulatory system.
D. Blood flows in one direction only through the circulatory system.

In 1959, doctors began using the powerful antibiotic methicillin to treat infections of staphylococcus aureus, but within two years, methicillin-resistant strains of s. aureus (mrsa) appeared. how did the resistant strains of s. aureus emerge? in 1959, doctors began using the powerful antibiotic methicillin to treat infections of staphylococcus aureus, but within two years, methicillin-resistant strains of s. aureus (mrsa) appeared. how did the resistant strains of s. aureus emerge? staphylococcus aureus bacteria that were able to synthesize cell walls using a protein that was not affected by methicillin survived the methicillin treatments and reproduced at higher rates than did other individuals. over time, these resistant individuals became increasingly common. in response to treatment of staphylococcus aureus infections with methicillin, some bacteria began to synthesize cell walls using a protein that was not affected by methicillin. these bacteria survived the methicillin treatments and reproduced at higher rates than did other individuals. over time, these resistant individuals became increasingly common. in response to treatment of staphylococcus aureus infections with methicillin, bacterial populations gradually began to synthesize cell walls using a protein that was not affected by methicillin.