What phenomenon occurs when a wave encounters a change in medium causing a change in its speed and direction?

Correct Answer: A

Rationale: Refraction is the phenomenon that occurs when a wave encounters a change in medium, causing a change in its speed and direction. This change in speed and direction is due to the wave bending as it passes from one medium to another with a different density. It is essential to understand refraction as it plays a crucial role in various phenomena, such as the bending of light in lenses, the formation of rainbows, and the way seismic waves travel through the Earth's layers. Reflection, while also a wave phenomenon, involves the bouncing back of a wave when it encounters a boundary. Diffraction refers to the bending of waves around obstacles or through openings, and interference involves the combination of two or more waves to form a new wave pattern.

Correct Answer: B

Rationale: Convergent evolution refers to the process by which different species independently evolve similar traits or characteristics due to similar environmental pressures. In the case of bats and birds, both have evolved wings for flight despite not sharing a recent common ancestor with wings. Bats are mammals, while birds are avians, yet they both have wings adapted for flight, which is a classic example of convergent evolution. A) Humans and chimpanzees share a common ancestor and have not independently evolved similar traits. C) Dolphins and sharks are not closely related, and their similarities are due to adaptations to their aquatic environment rather than convergent evolution. D) Snakes and earthworms belong to different classes (reptiles and annelids, respectively) and do not share recent common ancestors, making their similarities not a result of convergent evolution.

Correct Answer: B

Rationale: - A) Ecosystem refers to a biological community of interacting organisms and their physical environment. - B) Community specifically refers to a group of organisms of different species living in the same place and interacting with each other. - C) Population refers to a group of individuals of the same species living in the same area. - D) Niche refers to the role or function of an organism or species within an ecosystem. In this context, the term for a group of organisms living in the same place and interacting with each other is best described as a community because it involves multiple species interacting within a shared habitat.

Correct Answer: C

Rationale: A chemical change involves a chemical reaction where new substances are formed. Burning wood to produce ash is an example of a chemical change because the wood undergoes a chemical reaction to form a new substance (ash). In this process, the chemical composition of wood changes to produce ash, which is a new substance. On the other hand, melting ice to form water, dissolving sugar in water, and crushing a can to reduce its size are examples of physical changes. In these instances, the substances may change their physical state or appearance but do not undergo a chemical reaction to form new substances. Therefore, choice C is the correct answer as it represents a chemical change, while choices A, B, and D represent physical changes.

Correct Answer: C

Rationale: The correct answer is C, Density. Density is a physical property of a substance that remains constant regardless of the amount of the substance present. Mass (Choice A) is the amount of matter in an object and can change depending on the amount of the substance. Weight (Choice B) is the force exerted on an object due to gravity and can vary with location. Volume (Choice D) is the amount of space occupied by a substance and can change if the amount of the substance changes.