HESI A2 Biology Version 1 Questions

Explanation

<h2>Strep throat is caused by a bacterium.</h2> Strep throat is a bacterial infection that causes inflammation and pain in the throat. This disease is caused by Streptococcus pyogenes, also known as Group A Streptococcus (GAS), a bacterium that can be spread through direct contact with mucus from the nose or throat of people who are sick with strep throat or through contact with infected wounds or sores on the skin. <b>A) Mumps</b> Mumps is not caused by a bacterium. Instead, it is a viral infection that primarily affects the parotid glands — one of three pairs of saliva-producing (salivary) glands, situated below and in front of your ears. Hence, this choice is incorrect. <b>B) Strep throat</b> Strep throat is indeed caused by a bacterium, specifically Streptococcus pyogenes, or group A streptococcus. This bacterium is responsible for the sore and inflamed throat that characterizes this condition. This makes strep throat the correct choice. <b>C) AIDS (HIV+)</b> AIDS, which stands for Acquired Immune Deficiency Syndrome, is caused by the Human Immunodeficiency Virus (HIV). HIV is a type of virus, not a bacterium, making this choice incorrect. <b>D) Common cold</b> The common cold is a viral infection, not a bacterial one. It is primarily caused by rhinoviruses, along with numerous other viral species. Therefore, this choice is incorrect. <b>Conclusion</b> The only disease among the options that is caused by a bacterium is strep throat. Mumps, AIDS (HIV+), and the common cold are all caused by viruses, not bacteria. It's crucial to know the difference because treatment approaches for bacterial and viral infections can differ significantly: bacterial infections can often be cured with antibiotics, while viral infections generally have to run their course.

Explanation

<h2>Flagellum enables cells to move through their environments.</h2> Flagella are long, whip-like appendages that protrude from the cell body and are used by cells to propel themselves in their environment. They can be found in both prokaryotic and eukaryotic cells, and they function by rotating like a propeller, which enables the cell to move. <b>A) Flagellum</b> A flagellum is a long, whip-like structure that protrudes from the cell body and is used for locomotion. In prokaryotes, the flagellum spins like a propeller to propel the cell through liquid environments. In eukaryotes, the flagellum undulates in a wave-like motion to move the cell. <b>B) Cell membrane</b> The cell membrane is a protective barrier that surrounds the cell and regulates the passage of substances in and out of the cell. Although it plays a crucial role in maintaining homeostasis and communication between cells, it does not facilitate movement through the environment. <b>C) Transport protein</b> Transport proteins are embedded within the cell membrane and facilitate the movement of substances across the membrane. These proteins are responsible for the selective permeability of the cell membrane, allowing certain molecules to enter or exit the cell. However, they do not contribute to the physical movement of the cell itself. <b>D) Receptor</b> Receptors are proteins located on the cell surface or within the cell that bind to specific molecules, triggering a response within the cell. While they play a critical role in cell signaling and communication, they do not enable cell mobility. <b>Conclusion</b> In conclusion, the flagellum is the only cellular appendage that helps cells move through their environments. While cell membranes, transport proteins, and receptors play essential roles in various cellular functions, they do not contribute to cell movement. Thus, the flagellum serves as the primary structure for cellular locomotion.

Explanation

<h2>Sex cells undergo the process of Meiosis to reproduce.</h2> Meiosis is a type of cell division that results in four daughter cells each with half the number of chromosomes of the parent cell. This is essential for sexual reproduction as it ensures the offspring has the correct number of chromosomes. <b>A) Meiosis</b> Meiosis is the correct answer. In sexually reproducing organisms, meiosis is the specialized form of cell division that generates gametes, which are the sex cells (sperm in males, eggs in females). Meiosis reduces the number of chromosomes by half from the parent cell to the offspring, allowing for genetic diversity and the maintenance of the species' chromosome number across generations. <b>B) Cytokinesis</b> Cytokinesis is not the correct answer. While cytokinesis is a stage of cell division, it is the physical process where the cytoplasm of a parent cell divides into two daughter cells. It occurs after mitosis in somatic cells and after meiosis in sex cells. It is not the process sex cells undergo to reproduce, but rather a step in the process. <b>C) Fission</b> Fission is not the correct answer. Fission is a form of asexual reproduction, typically seen in single-celled organisms like bacteria and some protists. It does not involve the reduction of chromosome number or the production of sex cells, hence it is not the process sex cells undergo to reproduce. <b>D) Mitosis</b> Mitosis is not the correct answer. Mitosis is a process of cell division that results in two genetically identical daughter cells, each with the same number of chromosomes as the parent cell. This process is used for growth and repair in multicellular organisms, not for the reproduction of sex cells. <b>Conclusion</b> In conclusion, the process that sex cells undergo to reproduce is Meiosis. While cytokinesis and mitosis are involved in other types of cell division and growth processes, and fission is a method of asexual reproduction, only meiosis is responsible for the production and genetic variation of sex cells in sexually reproducing organisms. This ensures genetic diversity and the maintenance of the correct number of chromosomes in the offspring.

Explanation

<h2>A hypertonic solution has a higher concentration of solutes than the cell's.</h2> In the context of osmosis and cell biology, solutions are typically described as isotonic, hypotonic, or hypertonic. These terms refer to the relative concentration of solutes (substances dissolved in a liquid) in a solution compared to the interior of a cell. If a solution is hypertonic, it has a higher solute concentration than the cell. <b>A) Same as</b> If a solution had the same solute concentration as the cell, it would be described as isotonic, not hypertonic. In an isotonic solution, there is no net movement of water into or out of the cell, since the osmotic pressures inside and outside the cell are equal. <b>B) Lower than</b> A solution with a lower solute concentration than the cell is described as hypotonic, not hypertonic. In a hypotonic solution, water tends to move into the cell, which can cause the cell to swell and potentially burst. <b>C) Higher than</b> A hypertonic solution has a higher concentration of solutes compared to the cell. In this environment, water tends to move out of the cell to try and equalize the concentration of solutes. This can result in the cell shrinking or shriveling due to water loss. <b>D) Negative</b> A solution's solute concentration cannot be negative. This term doesn't apply in the context of comparing solute concentrations. <b>Conclusion</b> A hypertonic solution has a higher concentration of solutes than the cell's interior. This causes water to move out of the cell in an attempt to equalize the concentration of solutes, which can lead to the cell shrinking or shriveling. The other options described either an isotonic solution (same solute concentration), a hypotonic solution (lower solute concentration), or a non-applicable situation (negative solute concentration).

Explanation

<h2>The aerodynamic nature of a bird's wing is best categorized under structure and function in biology.</h2> This category focuses on the physical characteristics of an organism (structure) and how these characteristics enable the organism to survive, grow, and reproduce (function). The aerodynamic shape of a bird's wing is a clear example of this relationship, as its structure allows for flight, which in turn aids in finding food, evading predators, and reaching suitable habitats for nesting. <b>A) Organisms and their environment</b> This category refers to the interactions between organisms and their surroundings, including other species and abiotic factors. While the ability to fly can influence how a bird interacts with its environment, the aerodynamic nature of the bird's wing itself is more directly related to its physical structure and function, rather than its relationship with the environment. <b>B) Ontogeny</b> Ontogeny pertains to the development of an organism from the fertilized egg to its mature form. It involves processes like growth, cell differentiation and morphogenesis. While the development of a bird's wing is part of its ontogeny, the aerodynamics of the wing is a feature that falls under the category of structure and function. <b>C) Structure and function</b> The structure and function category in biology refers to the relationship between the physical characteristics of an organism and their role in survival, growth, and reproduction. The aerodynamic nature of a bird's wing is a key example of this relationship—its specific structure allows the bird to fly, which is essential for its survival and reproduction. <b>D) Heredity</b> Heredity refers to the transmission of genetic characteristics from parents to offspring. Although the genes a bird inherits from its parents will determine the potential for developing wings, the aerodynamic nature of the wings is a feature that is best categorized under structure and function, not heredity. <b>Conclusion</b> In biology, the aerodynamic nature of a bird's wing falls under the category of structure and function. This is because the wing's structure, being streamlined and feathered, allows the bird to fly—an essential function for its survival and reproduction. While the bird's wing development and its relationship with the environment are important biological aspects, they do not best categorize the aerodynamics of the wing. Similarly, although heredity plays a role in the bird's potential to develop wings, it doesn't categorize the aerodynamics of the wing.