Nokea
What is the term for an organism with two different alleles for a gene?
- A. Homozygous
- B. Heterozygous
- C. Dominant
- D. Recessive
Correct Answer: B
Rationale: Homozygous refers to an organism with two identical alleles for a gene, either both dominant or both recessive. Heterozygous, the correct answer, refers to an organism with two different alleles for a gene, one dominant and one recessive. Dominant and recessive describe the relationship between alleles, where dominant alleles are expressed over recessive alleles in heterozygous individuals. Therefore, the term for an organism with two different alleles for a gene is 'heterozygous.'
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Which property of a substance refers to its ability to be stretched into thin wires without breaking?
- A. Conductivity
- B. Viscosity
- C. Ductility
- D. Malleability
Correct Answer: C
Rationale: Ductility is the property of a substance that allows it to be stretched into thin wires without breaking. This property is distinct from the other options provided. Conductivity refers to the ability to conduct electricity or heat, viscosity refers to a liquid's resistance to flow, and malleability refers to the ability of a substance to be hammered or rolled into thin sheets. Therefore, the correct answer is 'Ductility.'
What phenomenon explains the formation of rainbows in the sky?
- A. Diffraction
- B. Interference
- C. Refraction and dispersion of sunlight by water droplets
- D. Reflection from clouds
Correct Answer: C
Rationale: Rainbows are formed due to the refraction and dispersion of sunlight by water droplets in the atmosphere. When sunlight enters a water droplet, it is refracted, then internally reflected, and finally refracted again as it exits the droplet. This dispersion of light into its component colors creates the beautiful rainbow we see in the sky. Choice A, diffraction, involves bending of light around obstacles or through narrow openings, not the splitting of light into colors as seen in rainbows. Choice B, interference, refers to the phenomenon where two or more light waves overlap and interact, producing a pattern of light and dark bands, which is not the case with rainbows. Choice D, reflection from clouds, does not accurately describe the process involved in the formation of rainbows through refraction and dispersion of light by water droplets.
During micturition, the process involves a combination of:
- A. Gravity alone
- B. Voluntary muscle contractions only
- C. Involuntary muscle contractions only
- D. Both voluntary and involuntary muscle contractions
Correct Answer: D
Rationale: During micturition, which is the process of urination, both voluntary and involuntary muscle contractions are involved. Voluntary muscle contractions include the relaxation of the external urethral sphincter, allowing the release of urine, while involuntary muscle contractions involve the detrusor muscle in the bladder contracting to expel urine. Choices A, B, and C are incorrect because micturition is not solely dependent on gravity, voluntary muscle contractions, or involuntary muscle contractions alone. The correct answer is D as both types of muscle contractions are necessary for the complete process of urination.
Which of the following scenarios represents an example of static friction?
- A. Sliding a heavy box across the floor
- B. A car moving around a curve
- C. Pushing a stationary object
- D. Braking a car to stop
Correct Answer: C
Rationale: The correct answer is C. Static friction occurs when two surfaces are in contact but not moving relative to each other. Pushing a stationary object involves static friction as you apply a force to overcome the friction keeping the object stationary. Choices A, B, and D involve kinetic friction, which occurs when two surfaces are moving relative to each other. Option A involves moving the box across the floor, which is an example of kinetic friction. Option B involves the movement of a car around a curve, which also relates to kinetic friction due to the relative movement between the tires and the road. Option D describes braking a car to stop, where the moving car's wheels interact with the road, creating kinetic friction to slow down and stop the car.
What is the feedback mechanism in the endocrine system that helps maintain hormone balance?
- A. Positive feedback, where a hormone stimulates its own release
- B. Negative feedback, where a hormone suppresses its own release
- C. Cascade effect, where one hormone triggers the release of another
- D. Dual hormone system, where two hormones work together
Correct Answer: B
Rationale: In the endocrine system, negative feedback is the mechanism by which hormone levels are regulated. When hormone levels reach a certain threshold, they signal the body to stop producing more of that hormone, thus maintaining a balance. Negative feedback (option B) is the correct answer as it helps in preventing overproduction of hormones by suppressing their own release. Positive feedback (option A) would lead to an excessive production of hormones, disrupting the balance. The cascade effect (option C) involves one hormone triggering the release of another but does not directly regulate hormone levels. The dual hormone system (option D) refers to two hormones working together but does not specifically address the feedback mechanism for maintaining hormone balance.