When an atom gains or loses electrons, it becomes a(n):
- A. Molecule
- B. Isotope
- C. Ion
- D. Compound
Correct Answer: C
Rationale: When an atom gains or loses electrons, it becomes an ion. Gaining or losing electrons alters the atom's electron count and charge, creating a positively or negatively charged ion. A molecule is formed when two or more atoms are chemically bonded. An isotope is a variation of an element with a different number of neutrons. A compound consists of two or more different elements chemically bonded together.
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Which nervous system controls the involuntary 'fight-or-flight' response?
- A. Sympathetic nervous system
- B. Parasympathetic nervous system
- C. Enteric nervous system
- D. Sensory nervous system
Correct Answer: A
Rationale: The correct answer is the sympathetic nervous system. The sympathetic nervous system is responsible for activating the body's response to stress or danger, leading to the 'fight-or-flight' response. It prepares the body for action by increasing heart rate, dilating pupils, and redirecting blood flow to muscles. Choice B, the parasympathetic nervous system, is responsible for the body's 'rest-and-digest' activities, which are opposite to the 'fight-or-flight' response. Choice C, the enteric nervous system, primarily regulates the gastrointestinal system and is not directly involved in the 'fight-or-flight' response. Choice D, the sensory nervous system, transmits sensory information from the body to the central nervous system and is not responsible for the physiological changes associated with the 'fight-or-flight' response.
Which of the following is an example of stabilizing selection?
- A. Selection that favors extreme traits in a population
- B. Selection that removes individuals with extreme traits
- C. Selection that maintains the current average trait in a population
- D. Selection that favors one specific trait over all others
Correct Answer: C
Rationale: - Stabilizing selection is a type of natural selection that favors the intermediate variants in a population, while selecting against the extreme traits. This results in the maintenance of the current average trait in the population.
- Option A is incorrect because stabilizing selection does not favor extreme traits; instead, it favors the average trait.
- Option B is incorrect because stabilizing selection does not remove individuals with extreme traits; it acts against extreme traits by favoring the intermediate variants.
- Option D is incorrect because stabilizing selection does not favor one specific trait over all others; it favors the average trait by selecting against extreme traits.
What is the term for the small air sacs in the lungs where gas exchange (oxygen and carbon dioxide) takes place?
- A. Bronchi
- B. Alveoli
- C. Trachea
- D. Bronchioles
Correct Answer: B
Rationale: The correct answer is B: Alveoli. The alveoli are the small air sacs in the lungs where gas exchange occurs. Oxygen from the air we breathe passes into the bloodstream through the alveoli, while carbon dioxide from the bloodstream passes out of the body through the alveoli. Choice A, Bronchi, are the main airways in the lungs and not the site of gas exchange. Choice C, Trachea, refers to the windpipe, which is a different structure than the alveoli. Choice D, Bronchioles, are smaller airways branching off from the bronchi and are not where gas exchange primarily occurs.
What is a group of organisms of the same species living in a particular area called?
- A. Community
- B. Population
- C. Ecosystem
- D. Habitat
Correct Answer: B
Rationale: A) Community refers to all the populations of different species living and interacting in a particular area. Since the question specifies organisms of the same species, community is not the correct answer. B) Population is a group of organisms of the same species living in a particular area. This term specifically refers to individuals of the same species and their interactions within a defined area. C) Ecosystem includes all the living organisms (biotic factors) and non-living components (abiotic factors) in a particular area and their interactions. While populations are part of an ecosystem, the term 'ecosystem' is broader and includes multiple populations. D) Habitat refers to the specific environment where an organism lives, including the physical and biological factors. It is the place where a population or individual organism resides, but it does not specifically refer to a group of organisms of the same species.
Which part of the neuron receives signals from other neurons and conducts them toward the cell body?
- A. Axon
- B. Dendrite
- C. Synapse
- D. Myelin sheath
Correct Answer: B
Rationale: The dendrites are the part of the neuron that receives signals from other neurons and conducts them toward the cell body. They play a crucial role in gathering incoming signals and transmitting them to the cell body for processing. The axon, on the other hand, is responsible for carrying signals away from the cell body. The synapse is the point of connection between two neurons facilitating communication, while the myelin sheath is a protective layer surrounding the axon that aids in accelerating signal transmission.