The early atmosphere of Earth did not contain the gas ________; it is believed that life as we know it would not have evolved if this gas had been present
Fill in the blank(s) with correct word
oxygen or O2 (either term can be used here)
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A population of T cells has been stimulated to proliferate in response to a particular antigen. A sample of 1000 cells is examined microscopically, revealing that 200 of these cells are in the various stages of mitosis. Of the remaining 800 in interphase, 400 have x amount of DNA, 250 have 2x, and the remaining 150 have amounts somewhere between x and 2x. Additional analysis reveals that the G2
phase of the cell cycle lasts 2 hours. What is the total length of the cell cycle? A) 2.5 hours B) 4 hours C) 6.4 hours D) 8 hours E) 13.3 hours
Respond to statements 166–169 in reference to the autonomic
nervous system associated with the five regions of the human spinal cord listed below. a. cervical b. thoracic c. lumbar d. sacral e. coccygeal D 166. Sympathetic nerves from this region innervate the bladder, uterus, and genitals. D 167. Sympathetic nerves from this region innervate the kidney. D 168. Parasympathetic nerves from this region innervate the rectum. D 169. Sympathetic nerves from this region innervate the heart.
A typical human body cell with 23 pairs of chromosomes is called a __________.
A. sister cell B. somatic cell C. haploid cell D. gamete
Which of the following is responsible for the alpha-helical structure of proteins?
a. hydrophobic interactions b. nonpolar covalent bonds c. ionic interactions d. hydrogen bonds e. polar covalent bonds