Nokea
Which of the following structures is responsible for transmitting electrical impulses in the nervous system?
- A. Neuron
- B. Axon
- C. Myelin
- D. Dendrite
Correct Answer: A
Rationale: The correct answer is A: Neuron. Neurons are specialized cells that transmit electrical impulses in the nervous system. While the axon is the part responsible for conducting these impulses over long distances, it is the neuron as a whole that is ultimately responsible for transmitting electrical impulses. Myelin is a fatty substance that surrounds and insulates axons, speeding up signal transmission. Dendrites, on the other hand, receive signals from other neurons. Therefore, although the axon plays a significant role in transmission, the neuron is the fundamental unit responsible for transmitting electrical impulses in the nervous system.
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What is the primary source of energy entering most ecosystems?
- A. Chemical energy stored in bonds
- B. Thermal energy from the Earth's core
- C. Light energy from the sun
- D. Kinetic energy from wind and water
Correct Answer: C
Rationale: In most ecosystems, the primary source of energy is sunlight. This energy is captured by plants and other photosynthetic organisms through the process of photosynthesis. These organisms convert light energy into chemical energy stored in the bonds of organic molecules, such as glucose. This stored chemical energy is then passed on to other organisms in the ecosystem through the food chain, making sunlight the fundamental source of energy for most ecosystems. Thermal energy from the Earth's core (option B) is not a primary source of energy for ecosystems, as it is not readily accessible to most organisms. Kinetic energy from wind and water (option D) can play a role in some ecosystems, but it is not the primary source of energy. Chemical energy stored in bonds (option A) is a form of energy that is ultimately derived from the sun through photosynthesis, making it a product of the primary energy source rather than the primary source itself.
What is the term for a solution that has exactly the same concentration of solute as another solution?
- A. Saturated solution
- B. Unsaturated solution
- C. Isotonic solution
- D. Concentrated solution
Correct Answer: C
Rationale: An isotonic solution is a solution that has the same concentration of solute as another solution. When cells are placed in an isotonic solution, there is no net movement of water across the cell membrane, maintaining equilibrium. Choice A, a saturated solution, refers to a solution that contains the maximum amount of solute that can be dissolved at a given temperature. Choice B, an unsaturated solution, is a solution that contains less solute than a saturated solution under the same conditions. Choice D, a concentrated solution, is a solution with a high amount of solute compared to the solvent.
What phenomenon is responsible for the mirage effect seen in deserts?
- A. Diffraction
- B. Refraction
- C. Interference
- D. Polarization
Correct Answer: B
Rationale: Refraction is the bending of light as it passes from one medium to another of different density. In deserts, the temperature gradient causes light to bend, creating the mirage effect where distant objects appear distorted or displaced. Diffraction refers to the bending of light around obstacles or apertures, not the cause of mirages. Interference involves the superposition of two or more waves, which is not the mechanism behind mirages. Polarization refers to the orientation of light waves in a specific plane and is not responsible for the mirage effect in deserts. Therefore, the correct answer is refraction.
Which of the following statements about fungi is FALSE?
- A. They can be unicellular or multicellular
- B. They are all parasitic and cause disease in humans
- C. They play a vital role in decomposition and nutrient cycling
- D. Some are used in food production, like mushrooms
Correct Answer: B
Rationale: A) This statement is true. Fungi can exist in both unicellular (yeast) and multicellular (molds and mushrooms) forms.
B) This statement is false. While some fungi can be parasitic and cause diseases in humans, not all fungi exhibit this behavior. Many fungi are beneficial and play essential roles in ecosystems.
C) This statement is true. Fungi are crucial for decomposition and nutrient cycling in ecosystems. They break down organic matter and recycle nutrients back into the environment.
D) This statement is true. Some fungi, like mushrooms, are used in food production and are consumed by humans.
The spleen, a large lymphatic organ, is located in the:
- A. Chest
- B. Abdomen
- C. Pelvis
- D. Head and neck
Correct Answer: B
Rationale: The spleen is located in the abdomen, specifically in the upper left part of the abdomen, under the ribcage and above the stomach. It is an important organ in the lymphatic system responsible for filtering blood, storing blood cells, and fighting infection. It is not located in the chest, pelvis, or head and neck regions. Therefore, the correct answer is 'B: Abdomen.' Choices 'A: Chest,' 'C: Pelvis,' and 'D: Head and neck' are incorrect as the spleen is not situated in these anatomical areas.