1. 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.

2. What happens to the kinetic energy of an object when its mass is doubled?

A. Kinetic energy remains the same
B. Kinetic energy halves
C. Kinetic energy doubles
D. Kinetic energy quadruples

Correct answer: c

Rationale: Kinetic energy is directly proportional to the square of an object's mass when its velocity remains constant.

3. During antibiotic use, bacteria can evolve resistance. This is an example of:

A. Coevolution (two species influencing each other's evolution)
B. Convergent evolution (unrelated organisms evolving similar traits)
C. Macroevolution (large-scale evolutionary change)
D. Artificial selection acting on a natural process

Correct answer: D

Rationale: Rationale: - Coevolution (option A) refers to the influence of two species on each other's evolution, which is not the case in the scenario described in the question. - Convergent evolution (option B) involves unrelated organisms evolving similar traits due to similar environmental pressures, which is not directly applicable to the situation of bacteria evolving resistance to antibiotics. - Macroevolution (option C) refers to large-scale evolutionary changes over long periods, which is not specifically demonstrated in the context of bacteria evolving resistance during antibiotic use. - The process of bacteria evolving resistance to antibiotics due to the selective pressure exerted by the antibiotics is an example of artificial selection (human intervention selecting for certain traits) acting on a natural process (bacterial evolution). Antibiotic use creates a selective pressure that favors the survival and reproduction of bacteria with resistance traits, leading to the evolution of an

4. In a neutral atom, the number of electrons:

A. Must be equal to the number of protons.
B. Must be less than the number of protons.
C. Must be greater than the number of neutrons.
D. Can vary depending on the atom's temperature.

Correct answer: A

Rationale: Must be equal to the number of protons - For electrical neutrality, the positive charge of protons must be balanced by the negative charge of an equal number of electrons.

5. Isotopes are variants of a single element that differ in:

A. Having the same number of protons but varying numbers of neutrons
B. Having the same number of neutrons but varying numbers of protons
C. Having the same mass but different atomic numbers
D. None of the above

Correct answer: A

Rationale: The correct answer is A: 'Having the same number of protons but varying numbers of neutrons.' Isotopes are atoms of the same element with the same number of protons (which determines the element) but different numbers of neutrons. This results in isotopes having slightly different atomic masses. Options B and C are incorrect because isotopes specifically refer to variations in the number of neutrons, not protons or atomic numbers. Option D is incorrect because isotopes do exist due to differences in neutron number.

6. What happens when an atom loses an electron?

A. It becomes a molecule.
B. It gains a positive charge and becomes an ion.
C. It changes its element identity.
D. Nothing happens, it remains neutral.

Correct answer: B

Rationale: It gains a positive charge and becomes an ion. Losing an electron disrupts the charge balance, leaving the atom with more protons than electrons and a positive charge.