in order from lower to upper the layers of the atmosphere are
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HESI A2

HESI A2 Biology Practice Test

1. In order, from lower to upper, the layers of the atmosphere are:

Correct answer: B

Rationale: The correct order of the layers of the atmosphere, from lower to upper, is troposphere, stratosphere, mesosphere, thermosphere, exosphere. The troposphere is the lowest layer where weather phenomena occur. The stratosphere contains the ozone layer, which absorbs and scatters the solar ultraviolet radiation. The mesosphere is where most meteorites burn up upon entering the Earth's atmosphere. The thermosphere is characterized by high temperatures due to the absorption of solar radiation. The exosphere is the outermost layer where the atmosphere transitions into space. Therefore, option B is the correct sequence, as it reflects the ascending order of the Earth's atmospheric layers.

2. In the scientific process, which of the following is a statement or explanation of certain events or happenings?

Correct answer: A

Rationale: A hypothesis is a statement or explanation of certain events or phenomena based on observations and prior knowledge. It is a testable prediction that guides the scientific investigation process. By formulating a hypothesis, scientists can make predictions and design experiments to gather data and test the validity of the hypothesis. Observations (choice B) involve gathering information through the senses. Experiments (choice C) are procedures carried out to support or refute a hypothesis. Conclusions (choice D) are deductions made based on the results of experiments and observations, but they are not the initial statement or explanation of events or happenings.

3. What are saturated fats saturated with?

Correct answer: A

Rationale: Saturated fats are saturated with hydrogen atoms. This means that each carbon atom in the fatty acid chains forming saturated fats is bonded to as many hydrogen atoms as possible. This saturation results in the fatty acid chains being straight and closely packed together, making saturated fats solid at room temperature. Choice B (Carbon atoms), C (Oxygen atoms), and D (Nitrogen atoms) are incorrect because saturated fats are specifically saturated with hydrogen atoms, not carbon, oxygen, or nitrogen atoms.

4. What kind of bond connects sugar and phosphate in DNA?

Correct answer: C

Rationale: Sugar and phosphate are indeed connected by covalent bonds in DNA. Covalent bonds involve the sharing of electrons between atoms, which is essential for forming the backbone of the DNA molecule. Hydrogen bonds (Choice A) are important in holding the nitrogenous bases together in the DNA double helix but do not connect sugar and phosphate. Ionic bonds (Choice B) involve the transfer of electrons between atoms and are not the primary bond connecting sugar and phosphate in DNA. 'Overt' (Choice D) is not a type of chemical bond and is an incorrect distractor.

5. Which component of the cell contributes to the protection, communication, and passage of substances into and out of the cell?

Correct answer: B

Rationale: The correct answer is the cell membrane. The cell membrane is responsible for protecting the cell, facilitating communication with the external environment, and regulating the passage of substances into and out of the cell. The nucleus (Choice A) is the control center of the cell and houses the genetic material but is not primarily involved in these functions. The endoplasmic reticulum (Choice C) is involved in protein synthesis and lipid metabolism, not primarily in protection or communication. The cytoplasm (Choice D) is the gel-like substance that fills the cell but does not specifically contribute to protection, communication, or substance passage.

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