Identify the opposing muscle pair.

Correct Answer: A

Rationale: The correct answer is A. The bicep and tricep muscles form an antagonistic muscle pair, where one muscle contracts while the other relaxes. The bicep, located on the front of the upper arm, is responsible for arm flexion (bending the elbow), while the tricep, situated on the back of the upper arm, is responsible for arm extension (straightening the elbow). This opposing action allows for controlled movement at the elbow joint. Choice B, hamstring and quadriceps, are not opposing muscles in the context of the knee joint; the hamstring group flexes the knee, while the quadriceps group extends it. Choices C and D do not represent an opposing muscle pair related to joint movement.

Correct Answer: A

Rationale: When a wave enters a different medium, its frequency remains constant. Frequency is an intrinsic property of the wave determined by its source, and it does not change when transitioning between different mediums. On the other hand, wavelength, amplitude, and speed of the wave can all be altered when the wave moves from one medium to another. Wavelength is dependent on the speed of the wave and can change when entering a different medium due to differences in propagation speed. Amplitude can also change as it is influenced by factors like energy loss or gain at the boundary of the mediums. Speed, determined by the medium's properties, typically changes when a wave transitions between different mediums due to variations in the medium's density and elasticity.

Correct Answer: B

Rationale: Biological classification, also known as taxonomy, is the science of categorizing and organizing living organisms based on shared characteristics. The main purpose of biological classification is not to create a rigid and unchanging system (option A) or to simplify nature into neat and tidy categories (option C). Instead, it aims to help us understand the diversity of life on Earth and how different organisms are related to each other. By classifying organisms into groups based on their evolutionary relationships, we can gain insights into the interconnectedness of life and better appreciate the complexity and beauty of the natural world. Assigning organisms to specific ecological niches (option D) is more related to ecological studies rather than biological classification.

Correct Answer: B

Rationale: A) Founder effect: This occurs when a small group of individuals establishes a new population, leading to a loss of genetic variation compared to the original population. It does not necessarily result in a gradual loss of genetic variation in an existing population. B) Bottleneck effect: This process occurs when a population is drastically reduced in size, leading to a significant loss of genetic variation due to the limited number of individuals contributing to the gene pool. The reduced genetic diversity can have long-term effects on the population's ability to adapt to environmental changes. C) Gene flow: This refers to the movement of genes between populations, which can introduce new genetic variation and prevent populations from diverging. Gene flow does not lead to a gradual loss of genetic variation within a population. D) Speciation: This is the process by which new species evolve from existing species, often involving the accumulation of genetic differences that l

Correct Answer: C

Rationale: During a physical change in matter, the original substance undergoes a change in its physical state or appearance without any change in its chemical composition. This means that the original substance can be recovered by physical means, such as melting, freezing, boiling, or condensing. No new substance is formed (option A), the chemical composition remains the same (option B), and energy changes can occur but are not a defining characteristic of a physical change (option D). The ability to recover the original substance by physical means distinguishes physical changes from chemical changes.