ATI TEAS 7 Science

Correct Answer: C

Rationale: The correct answer is C: GABA. GABA is an inhibitory neurotransmitter that slows down neuron activity by binding to GABA receptors, leading to hyperpolarization of the neuron and reducing the likelihood of firing an action potential. This process helps to prevent overexcitation in the nervous system. A: Acetylcholine is primarily an excitatory neurotransmitter involved in muscle control and cognitive function. B: Dopamine plays a role in reward-motivated behavior and movement, but it is not primarily responsible for slowing down neuron activity. D: Serotonin is involved in regulating mood, appetite, and sleep, but it does not directly slow down neuron activity to prevent overexcitation.

Correct Answer: A

Rationale: The correct answer is A: Hydrogen bonding. Water molecules exhibit hydrogen bonding, where the partially positive hydrogen of one water molecule is attracted to the partially negative oxygen of another water molecule. This strong intermolecular force leads to the cohesive forces that create high surface tension in water. B: London dispersion forces are weaker and do not contribute significantly to water's high surface tension. C: Ionic bonding involves the transfer of electrons between atoms, not relevant to water's surface tension. D: Metallic bonding occurs in metals and is not related to the surface tension of water.

Correct Answer: C

Rationale: The correct answer is C: Light energy from the sun. This is because photosynthesis, the process by which plants and other organisms convert light energy into chemical energy, is the primary source of energy in most ecosystems. Sunlight is essential for plants to produce food, which then sustains the entire food chain. Choice A (Chemical energy stored in bonds) is incorrect because this energy is a product of photosynthesis and not the primary source entering ecosystems. Choice B (Thermal energy from the Earth's core) is incorrect as it is not a significant source of energy for most ecosystems. Choice D (Kinetic energy from wind and water) is also incorrect as it is not the primary source of energy entering ecosystems, although it can play a role in some ecosystems.

Correct Answer: C

Rationale: The Law of Conservation of Energy states that energy cannot be created or destroyed, only transferred or transformed within a closed system. Therefore, the total amount of energy in a closed system remains constant over time. This is because energy is conserved and does not disappear or appear out of nowhere. The other choices are incorrect because energy does not increase (choice A) or decrease (choice B) in a closed system unless energy is coming in or going out of the system. The total energy in a closed system is independent of the temperature of the system (choice D) and is solely determined by the initial energy within the system and any energy transfers or transformations that occur within it.

Correct Answer: A

Rationale: The P wave on an ECG represents atrial depolarization. During the cardiac cycle, the electrical impulse originates in the sinoatrial (SA) node, causing the atria to contract. This depolarization of the atria is reflected as the P wave on the ECG. This occurs before the ventricles depolarize (choice B), repolarize (choice D), or before the atria repolarize (choice C). Therefore, the correct answer is A because the P wave specifically represents atrial depolarization in the cardiac cycle.