In your fertility clinic, you look at the lab results of a young man. He has a prostate gland the size of a golf ball, a fructose-rich semen, and 10 million sperm per ml. His sperm consist of little more than DNA, mitochondria, and a flagellum, with almost no cytoplasm. Also, he has follicle-stimulating hormone (FSH) and luteinizing hormone (LH) in his bloodstream. Which of these is the likely cause of his fertility problems?
A. enlarged prostate gland
B. fructose in the semen
C. sperm count
D. sperm morphology
E. FSH and LH
C. sperm count
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Active -galactosidase enzyme is observed only in E. coli growing in the presence of lactose. One hypothesis is that the enzyme is always being produced, but is produced in an unstable form that breaks down rapidly in the absence of lactose (hypothesis 1)
A second hypothesis is that the enzyme is stable, but is produced only in the presence of lactose (hypothesis 2). An experiment was performed to test these hypotheses. A culture of growing cells was exposed to lactose, which was later removed. The amount of -galactosidase present in the culture during the course of the experiment was measured. The data are shown in the graph below. Which one of the following statements is a conclusion that can be obtained from these experimental data? A. The amount of -galactosidase in the culture decreased rapidly after lactose was removed, in support of hypothesis 2. B. The amount of -galactosidase in the culture decreased rapidly after lactose was removed, in support of hypothesis 1. C. The amount of -galactosidase in the culture remained stable after lactose was removed, in support of hypothesis 1. D. Synthesis of -galactosidase is turned on when lactose is added and turned off when lactose is removed, in support of hypothesis 2. E. Synthesis of -galactosidase is turned on when lactose is added and turned off when lactose is removed, in support of hypothesis 1.
List the zones that comprise rocky shores. Which of the zones would you expect to have the highest species diversity and which would have the lowest species diversity? Explain your answer
What will be an ideal response?
A certain species of butterfly varies in color from white to dark blue. The birds found in the same area feed on the white or lightly colored butterflies, leaving butterflies that are darkly colored. This is an example of what type of selection?
A. directional selection B. stabilizing selection C. disruptive selection D. artificial selection
A measurement of a microbe is reported as 1 × 10-6 m, also known as
A) centimeters (cm). B) millimeters (mm). C) micrometers (?m). D) nanometers (nm). E) yards.