Correct Answer: D

Rationale: The correct answer is D: Red blood cell. Red blood cells, also known as erythrocytes, are specifically designed to carry oxygen throughout the body. They contain hemoglobin, a protein that binds to oxygen in the lungs and transports it to tissues and organs in the body. Nerve cells, muscle cells, and skin cells do not have the specialized function of carrying oxygen like red blood cells do. Nerve cells transmit electrical signals, muscle cells are involved in movement, and skin cells provide a protective barrier and regulate body temperature. Therefore, choices A, B, and C are incorrect in the context of carrying oxygen throughout the body.

Correct Answer: B

Rationale: The endomysium is the connective tissue layer that surrounds individual muscle fibers, providing support and aiding in the transmission of force generated during muscle contraction. It is crucial for maintaining the structural integrity of muscle fibers and facilitating the transmission of force within them. Tendons (option A) connect muscles to bones, perimysium (option C) surrounds bundles of muscle fibers known as fascicles, and epimysium (option D) encases the entire muscle. The endomysium specifically targets the structure that directly supports and aids in force transmission within individual muscle fibers, making it the correct answer in this context.

Correct Answer: A

Rationale: The medulla oblongata is a critical part of the brainstem responsible for regulating essential functions such as heart rate, breathing, and blood pressure. It houses centers that oversee these involuntary processes, making it the correct answer. The pons, midbrain, and thalamus do not primarily control heart rate and breathing, thus making them incorrect choices for this question.

Correct Answer: C

Rationale: A) Population refers to a group of individuals of the same species living in a specific area. B) Community refers to all the populations of different species living and interacting in a particular area. C) Biome is a large geographic area characterized by similar climate, plants, and animals. Biomes are defined by factors such as temperature, precipitation, and vegetation types. D) Ecosystem refers to a community of living organisms interacting with each other and their physical environment. An ecosystem can be part of a biome.

Correct Answer: B

Rationale: A) Trait: A trait is a characteristic or feature of an organism that is determined by its genes. B) Mutation: A mutation is a permanent alteration in the DNA sequence that can result from errors during DNA replication, exposure to mutagens, or other factors. C) Allele: An allele is a variant form of a gene that can result in different traits or characteristics. D) Variation: Variation refers to the differences in traits or characteristics among individuals of the same species, which can be influenced by genetic and environmental factors. In this context, the term that specifically refers to a permanent alteration in the DNA sequence is "mutation."