Nokea
What are the moon-shaped white structures at the base of fingernails called?
- A. Lunulae
- B. Cuticle
- C. Hyponychium
- D. Matrix
Correct Answer: A
Rationale: The correct answer is A: Lunulae. The moon-shaped white structures at the base of fingernails are known as lunulae. They are most prominent on the thumb and are situated at the base of the nail matrix. The lunula is the visible part of the nail matrix, which is responsible for generating new nail cells. Choice B, Cuticle, is incorrect as it refers to the thin layer of skin at the base of the nail plate. Choice C, Hyponychium, is incorrect as it is the skin that lies beneath the free edge of the nail. Choice D, Matrix, is incorrect as it is the area where the nail is formed, located under the cuticle.
You may also like to solve these questions
What is the term for a substance that can act as both a proton donor and a proton acceptor?
- A. Acid
- B. Base
- C. Amphiprotic
- D. Neutral
Correct Answer: C
Rationale: Amphiprotic substances are those that can both donate and accept protons. They possess characteristics of both acids and bases, making them capable of acting as proton donors and proton acceptors. Choices A and B represent substances that are specific to either donating or accepting protons. Choice D does not describe a substance's ability to donate or accept protons since neutrality does not inherently involve proton donation or acceptance.
Which of the following is the positively charged subatomic particle found in the nucleus of an atom?
- A. Electron
- B. Proton
- C. Neutron
- D. Quark
Correct Answer: B
Rationale: The correct answer is B: Proton. Protons are positively charged subatomic particles found in the nucleus of an atom. They have a mass of approximately 1 atomic mass unit (amu) and a charge of +1. The number of protons in an atom's nucleus determines the atomic number of the element, which is a unique identifier for each element. Choice A, Electron, is incorrect as electrons are negatively charged particles found outside the nucleus. Choice C, Neutron, is incorrect as neutrons are neutral particles found in the nucleus. Choice D, Quark, is incorrect as quarks are elementary particles that combine to form protons and neutrons, but they are not the positively charged particle found in the nucleus of an atom.
What is the periodic law?
- A. The statement that the properties of the elements are a periodic function of their atomic numbers.
- B. The statement that elements can be arranged in a table where elements with similar properties are grouped together.
- C. The statement that elements can be arranged in a table where the atomic number of an element is equal to the number of protons in its nucleus.
- D. The statement that elements can be arranged in a table where the atomic mass of an element is equal to the number of neutrons in its nucleus.
Correct Answer: A
Rationale: The periodic law states that the properties of elements are a periodic function of their atomic numbers. This means that when elements are arranged in order of increasing atomic number, there is a periodic repetition of their properties. This forms the basis for the modern periodic table. Option B describes the organization of elements in the periodic table, which is related to the periodic law but not the definition of it. Options C and D are incorrect as they describe concepts related to atomic structure (atomic number and atomic mass) rather than the periodic law itself.
When making a dilution, what do you do?
- A. Add more solvent to a concentrated solution
- B. Change the temperature of the solution
- C. Decrease the concentration of a solution
- D. All of the above
Correct Answer: C
Rationale: When making a dilution, you decrease the concentration of a solution by adding more solvent to a concentrated solution. This process does not involve changing the temperature of the solution, so option B is incorrect. Option A is also incorrect because you are not adding more solute to the solution during dilution. Therefore, the correct answer is C) Decrease the concentration of a solution. Options A and B are incorrect as dilution involves adding more solvent, not solute, and does not require changing the temperature of the solution.
Which of the following is NOT a recognized mode of natural selection?
- A. Directional selection (favoring one extreme trait value on a spectrum)
- B. Disruptive selection (favoring both extreme trait values on a spectrum)
- C. Stabilizing selection (favoring the average trait value on a spectrum)
- D. Sexual selection (selection based on mate choice that influences reproductive success)
Correct Answer: D
Rationale: A) Directional selection is a recognized mode of natural selection where one extreme trait value on a spectrum is favored over others, leading to a shift in the average trait value over time. B) Disruptive selection is a recognized mode of natural selection where both extreme trait values on a spectrum are favored over the average trait value, potentially causing the population to split into distinct groups. C) Stabilizing selection is a recognized mode of natural selection favoring the average trait value on a spectrum over extreme values, resulting in reduced genetic diversity. D) Sexual selection differs from traditional natural selection modes as it involves mate choice and competition for mates, not direct selection pressure on traits affecting survival and reproduction in the environment. Sexual selection can drive the evolution of traits enhancing an individual's attractiveness for mating purposes.