1. The fundamental units of structure and function in all living organisms, including humans, are termed:

A. Muscles
B. Organs
C. Tissues
D. Cells

Correct answer: D

Rationale: The correct answer is D: Cells. Cells are the fundamental units of structure and function in all living organisms, including humans. They are the building blocks of life, performing various functions necessary for an organism to survive and thrive. Muscles (A) are composed of muscle tissue, which is made up of muscle cells. Organs (B) are structures made up of different types of tissues working together. Tissues (C) are groups of cells that work together to perform specific functions within an organism. However, cells are the smallest unit of life and are responsible for carrying out all the essential processes needed for an organism to function.

2. The tiny contractile units within muscle cells are called:

A. Myocytes
B. Myofibrils
C. Sarcomeres
D. Tendons

Correct answer: C

Rationale: The correct answer is C: Sarcomeres. Sarcomeres are the basic contractile units within muscle cells. They are made up of overlapping filaments of actin and myosin proteins, which slide past each other during muscle contraction, resulting in muscle movement. Myocytes (A) are muscle cells, myofibrils (B) are cylindrical structures within muscle fibers composed of sarcomeres, and tendons (D) are tough bands of connective tissue that connect muscle to bone. Therefore, sarcomeres are specifically responsible for muscle contraction within muscle cells.

3. Biodiversity is important for healthy ecosystems because it:

A. Increases competition for resources
B. Provides stability and resilience to disturbances
C. Slows down nutrient cycling
D. Reduces the number of decomposers

Correct answer: B

Rationale: 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.

4. What is the main difference between white and brown adipose tissue?

A. Location only
B. Function and energy metabolism
C. Color only
D. Both white and brown have the same function

Correct answer: B

Rationale: The main difference between white and brown adipose tissue lies in their function and energy metabolism. White adipose tissue is primarily involved in energy storage, while brown adipose tissue is responsible for energy expenditure through thermogenesis. Brown adipose tissue contains a higher density of mitochondria and a unique protein called uncoupling protein 1 (UCP1) that allows for the generation of heat. This key distinction in function and energy metabolism sets white and brown adipose tissue apart, making option B the correct answer.

5. Which of the following best describes a chemical change?

A. Melting ice to form water
B. Dissolving sugar in water
C. Burning wood to produce ash
D. Crushing a can to reduce its size

Correct answer: c

Rationale: Chemical changes involve the formation of new substances with different chemical properties. Burning wood involves a chemical reaction where wood undergoes combustion, breaking down its chemical structure to produce new substances like ash and gases.

6. What is the difference between a sensory neuron and a motor neuron?

A. Sensory neurons carry signals away from the brain, while motor neurons carry signals towards the brain.
B. Sensory neurons control voluntary muscles, while motor neurons control involuntary muscles.
C. Sensory neurons are located in the peripheral nervous system, while motor neurons are located in the central nervous system.
D. Sensory neurons detect light, while motor neurons detect sound.

Correct answer: A

Rationale: The correct answer is A because sensory neurons are responsible for carrying signals from sensory receptors towards the central nervous system (brain and spinal cord), allowing us to perceive sensations such as touch, taste, smell, sight, and sound. On the other hand, motor neurons carry signals from the central nervous system to muscles and glands, enabling movement and responses. Therefore, sensory neurons carry signals away from the brain, while motor neurons carry signals towards the brain, making option A the most accurate choice among the options provided.