Nokea
When water boils, it changes from a liquid to a gas. This is an example of a:
- A. Chemical reaction
- B. Physical change
- C. Nuclear reaction
- D. Biological process
Correct Answer: B
Rationale: This is a physical change because boiling water involves a change in state from liquid to gas without altering the chemical composition of the water molecules. In a chemical reaction, new substances are formed by breaking and forming chemical bonds, which is not the case during boiling. A nuclear reaction involves changes in atomic nuclei, which are not occurring during boiling. A biological process refers to activities related to living organisms, which is not applicable to the change from liquid to gas in boiling water.
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What is the relationship between genetic drift and the founder effect?
- A. Founder effect is a cause of genetic drift within a small population
- B. Genetic drift is a cause of the founder effect in new populations
- C. They are the same phenomenon with different names
- D. They are unrelated concepts.
Correct Answer: A
Rationale: - The founder effect is a specific type of genetic drift that occurs when a small group of individuals establishes a new population, leading to a loss of genetic variation.
- Genetic drift, on the other hand, is a broader concept that refers to random changes in allele frequencies in a population over time due to chance events.
- Therefore, the founder effect is a specific scenario within the broader concept of genetic drift, where the establishment of a new population by a small number of individuals leads to genetic changes in the population.
Why is biodiversity important for healthy ecosystems?
- A. Increases stability and resilience to disturbances
- B. Provides stability and resilience to disturbances
- C. Slows down nutrient cycling
- D. Reduces the number of decomposers
Correct Answer: B
Rationale: Biodiversity refers to the variety of living organisms in a particular area. A diverse ecosystem is better able to withstand and recover from disturbances such as natural disasters, climate change, or human impacts. This is because different species play unique roles in the ecosystem, and a higher level of biodiversity means there are more species available to fulfill these roles. For example, if one species is negatively affected by a disturbance, other species may be able to compensate for its loss, maintaining the overall functioning of the ecosystem. Therefore, biodiversity provides stability and resilience to disturbances, making ecosystems healthier and more sustainable. Choice A is incorrect because biodiversity doesn't increase competition for resources but rather helps in maintaining a balance within the ecosystem. Choice C is incorrect as biodiversity does not slow down nutrient cycling; in fact, it enhances nutrient cycling by ensuring a variety of species involved in the process. Choice D is incorrect as biodiversity does not reduce the number of decomposers but instead supports a diverse community of decomposers that are essential for nutrient recycling in ecosystems.
Which of the following salt solutions is most likely to conduct electricity well?
- A. A saturated solution
- B. A concentrated solution of a strong electrolyte
- C. A dilute solution of a weak acid
- D. A mixture of a neutral compound and water
Correct Answer: B
Rationale: A concentrated solution of a strong electrolyte is most likely to conduct electricity well. Strong electrolytes completely dissociate into ions in solution, allowing for the flow of electric current. This high concentration of ions in the solution enhances its conductivity, making it a better conductor compared to other options. A saturated solution, although containing dissolved ions, may not have a high enough concentration to conduct electricity effectively. A dilute solution of a weak acid is a poor conductor as weak acids only partially dissociate into ions. A mixture of a neutral compound and water does not contain free ions necessary for conducting electricity.
What happens to the momentum of an object when there is no external force acting upon it?
- A. Momentum increases
- B. Momentum decreases
- C. Momentum remains constant
- D. Momentum becomes zero
Correct Answer: C
Rationale: When there is no external force acting upon an object, the law of conservation of momentum dictates that the momentum of the object remains constant. This means that the momentum does not increase or decrease; it stays the same. Choice A is incorrect because momentum does not increase. Choice B is incorrect because momentum does not decrease. Choice D is incorrect as momentum does not become zero; it remains constant as per the conservation law. Therefore, the correct answer is C, as the object's momentum is unchanged in the absence of external forces.
Which lifestyle practice can weaken the immune system?
- A. Getting enough sleep
- B. Eating a balanced diet rich in fruits and vegetables
- C. Managing stress levels
- D. Frequent smoking
Correct Answer: D
Rationale: Frequent smoking can weaken the immune system by damaging immune cells and impairing their function. Smoking increases the risk of respiratory infections and other illnesses, negatively impacting immune health. Therefore, frequent smoking is a lifestyle practice that can weaken the immune system. Choices A, B, and C are all beneficial practices that support a healthy immune system. Getting enough sleep, eating a balanced diet rich in fruits and vegetables, and managing stress levels are important for maintaining optimal immune function and overall well-being.