a child is sick they have a body temperature that exceeds 37c the body senses this and begins to sweat in order to lower the temperature what is this

HESI A2

HESI A2 Biology Practice Test

1. A child is sick. They have a body temperature that exceeds 37ºC. The body senses this and begins to sweat in order to lower the temperature. What is this an example of?

A. Positive feedback loop
B. Negative feedback loop
C. Both
D. None of the above

Correct answer: B

Rationale: This is an example of a negative feedback loop. In a negative feedback loop, the body's response (sweating) works to counteract the initial stimulus of a high body temperature by cooling the body down. The goal is to return the body to homeostasis, maintaining a stable internal environment. Positive feedback loops amplify the initial stimulus rather than counteracting it, which is not the case here. Therefore, choices A and C are incorrect. Choice D is also incorrect as the situation described fits the characteristics of a negative feedback loop.

2. How many pairs of chromosomes do all humans have?

A. 24 pairs
B. 23 pairs
C. 22 pairs
D. 20 pairs

Correct answer: B

Rationale: All humans have 23 pairs of chromosomes, totaling 46 chromosomes. Choice A is incorrect because humans do not have 24 pairs. Choice C is incorrect as humans have 23 pairs, not 22 pairs. Choice D is incorrect as humans have 23 pairs of chromosomes, not 20 pairs.

3. Phenotype refers to the _ of an individual.

A. Genetic makeup
B. Actual physical appearance
C. Recessive alleles
D. None of the above

Correct answer: B

Rationale: Phenotype refers to the actual physical appearance and characteristics of an individual, which are determined by the interaction of both genetic makeup (genotype) and environmental factors. It includes visible traits such as height, eye color, and hair type. Choice A, genetic makeup, refers to the genotype, which is the genetic constitution of an organism. Choice C, recessive alleles, is a specific type of gene variant and does not encompass the entire concept of phenotype. Choice D, none of the above, is incorrect as phenotype does refer to the actual physical appearance of an individual.

4. DNA bases include all but which of the following?

A. Adenine
B. Thymine
C. Uracil
D. Cytosine

Correct answer: C

Rationale: The correct answer is C: Uracil. Uracil is not a DNA base; it is a base found only in RNA. The four bases in DNA are Adenine, Thymine, Cytosine, and Guanine. Choice A, Adenine, is a correct DNA base. Choice B, Thymine, is a correct DNA base. Choice D, Cytosine, is a correct DNA base. Therefore, Uracil is the only incorrect choice among the options provided.

5. What provides the cell with the ability to move and propel?

A. Microfilaments
B. Microtubules
C. Flagella
D. Cilia

Correct answer: B

Rationale: Microtubules are the cellular structures responsible for cell movement and propulsion. Microtubules are part of the cytoskeleton and play a crucial role in various cellular processes, including cell motility and intracellular transport. While microfilaments also contribute to cell movement by enabling muscle contraction and cell shape changes, they are not primarily responsible for propelling the cell. Flagella and cilia are cellular appendages involved in cell movement, but they are composed of microtubules, making them the structures that move due to the actions of microtubules.