Nokea
Which of the following sets of valves is primarily responsible for preventing blood flow from major blood vessels to the heart?
- A. atrioventricular valves
- B. semilunar valves
- C. tricuspid valves
- D. bicuspid valves
Correct Answer: B
Rationale: The correct answer is B: semilunar valves. Semilunar valves are primarily responsible for preventing blood flow from major blood vessels to the heart. These valves are located at the base of the aorta and the pulmonary artery, ensuring blood flows in one direction only by closing when the ventricles relax to prevent blood from flowing back into the heart. Choices A, C, and D are incorrect. Atrioventricular valves (choice A) include the tricuspid and bicuspid valves, which prevent backflow between the atria and ventricles, not major blood vessels. Tricuspid valves (choice C) and bicuspid valves (choice D) are specific types of atrioventricular valves located between the atria and ventricles, not at the base of major blood vessels.
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Which of the following contains a single immature egg cell that is released during ovulation?
- A. oocytes
- B. follicles
- C. ovaries
- D. fallopian tubes
Correct Answer: B
Rationale: Follicles are the structures in the ovaries that contain the oocytes (immature egg cells). During ovulation, a single mature egg cell is released from a mature follicle in the ovary. The other options (A. oocytes, C. ovaries, D. fallopian tubes) do not specifically refer to the structure that contains the immature egg cell that is released during ovulation.
A scientist designs an experiment to test the hypothesis that exposure to more sunlight will increase the growth rate of elodea, a type of aquatic plant. The scientist has accumulated data from previous experiments that identify the average growth rate of elodea exposed to natural sunlight in the wild.
In the experiment set up, there are three tanks housing ten elodea each. Tank A is positioned in front of a window to receive natural sunlight similar to what elodea are exposed to; tank B is positioned in front of the same window but has an additional sunlight-replicating lamp affixed to it; and tank C is positioned in a dark corner with no exposure to natural sunlight.
The above experimental design description is an example of which of the following types of experiments?
- A. field experiment
- B. natural experiment
- C. controlled experiment
- D. observational study
Correct Answer: C
Rationale: The above experimental design description involves the manipulation of an independent variable (light exposure) to observe its effects on the dependent variable (plant growth) under controlled conditions. In a controlled experiment, researchers actively manipulate one or more variables while keeping all other variables constant to establish cause-and-effect relationships.
Choice A, a field experiment, typically takes place in a real-world setting but still involves manipulation and control of variables. Choice B, a natural experiment, involves observing naturally occurring differences in variables without researcher intervention. Choice D, an observational study, does not involve manipulation of variables, making it different from the described experimental design.
Which of the following choices would contain the code for making a protein?
- A. mRNA
- B. tRNA
- C. rRNA
- D. DNA polymerase
Correct Answer: A
Rationale: The correct answer is A: mRNA (messenger RNA). mRNA contains the genetic code or instructions for making a protein. During protein synthesis, mRNA carries the genetic information from DNA in the cell nucleus to the ribosomes, where proteins are synthesized. The sequence of nucleotides in mRNA corresponds to the sequence of amino acids that will be used to build the protein. Choice B, tRNA (transfer RNA), is involved in carrying amino acids to the ribosome during protein synthesis but does not contain the code for making a protein. Choice C, rRNA (ribosomal RNA), is a component of ribosomes where protein synthesis occurs but does not contain the specific code for making a protein. Choice D, DNA polymerase, is an enzyme involved in DNA replication, not in directly coding for protein synthesis.
Where does fertilization typically occur in the female reproductive system?
- A. uterus
- B. fallopian tube
- C. endometrium
- D. ovary
Correct Answer: B
Rationale: Fertilization typically occurs in the fallopian tube, specifically in the ampulla, which is the widest part of the tube. After ovulation, the released egg travels through the fallopian tube where it may encounter sperm for fertilization to take place. The fallopian tube provides the ideal environment for fertilization due to the presence of cilia that help move the egg and sperm towards each other. The uterus is where the fertilized egg will implant and develop into a fetus, not where fertilization occurs. The endometrium is the lining of the uterus that thickens to support a potential pregnancy but is not the site of fertilization. The ovary releases the egg during ovulation but is not where fertilization occurs.
How many neutrons are in an atom of the following element with a mass number of 50?
- A. 38
- B. 88
- C. 50
- D. 126
Correct Answer: C
Rationale: Neutrons are found in the nucleus of an atom along with protons. To determine the number of neutrons in an atom, subtract the atomic number (number of protons) from the mass number. In this case, the mass number given is 50. Since the atomic number is not specified, we can infer it from the choices provided. The mass number of an element represents the total sum of protons and neutrons in the nucleus. Therefore, the number of neutrons in this atom would also be 50, as the mass number is equivalent to the combined number of protons and neutrons, making choice C the correct answer. Choices A, B, and D are incorrect as they do not match the given mass number of 50.