the gram stain is a differential staining technique used to classify bacteria based on their cell wall composition gram positive bacteria appear
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ATI TEAS 7

TEAS 7 science practice

1. The Gram stain is a differential staining technique used to classify bacteria based on their cell wall composition. Gram-positive bacteria appear

Correct answer: D

Rationale: The Gram stain is a differential staining technique that categorizes bacteria into two groups based on their cell wall composition: Gram-positive and Gram-negative. Gram-positive bacteria have a thick layer of peptidoglycan in their cell walls, which retains the crystal violet stain used in the Gram staining procedure. Consequently, Gram-positive bacteria appear purple under the microscope after staining. On the other hand, Gram-negative bacteria possess a thinner peptidoglycan layer and an outer membrane that can be penetrated by the counterstain safranin, leading them to appear pink or red. Blue is not typically used to describe the color of bacteria in a Gram stain, making it an incorrect choice.

2. How many lobes does the right lung have?

Correct answer: C

Rationale: The correct answer is C: 3. The right lung consists of three lobes: the upper, middle, and lower lobes. This distinction is vital as the left lung only has two lobes, the upper and lower lobes. Understanding the anatomical variances between the lobes of the right and left lungs is crucial for comprehending respiratory physiology and its clinical implications in medical practice. Choices A, B, and D are incorrect because the right lung does not have 1, 2, or 4 lobes. It is essential to differentiate between the lobes of the right and left lungs to have a comprehensive understanding of pulmonary anatomy.

3. Which part of the digestive system is primarily responsible for absorbing nutrients?

Correct answer: B

Rationale: The small intestine is the primary site for nutrient absorption in the digestive system. It is lined with specialized cells that facilitate the absorption of nutrients such as carbohydrates, proteins, fats, vitamins, and minerals into the bloodstream for distribution throughout the body. While the stomach plays a role in digestion by breaking down food with acid and enzymes, the actual absorption of nutrients occurs mainly in the small intestine. The esophagus is responsible for transporting food from the mouth to the stomach, but it does not absorb nutrients. The large intestine primarily absorbs water and electrolytes, not nutrients.

4. How many tissue layers make up the uterus?

Correct answer: C

Rationale: The correct answer is C, 'Three.' The uterus is composed of three tissue layers: the endometrium, myometrium, and perimetrium. The endometrium is the innermost layer that thickens during the menstrual cycle and sheds during menstruation or supports a developing embryo during pregnancy. The myometrium is the middle layer, consisting of muscle tissue that contracts during labor. The perimetrium is the outer layer that covers the uterus. These three layers work together to support the functions of the uterus, such as menstruation, pregnancy, and labor. Choices A, B, and D are incorrect because the uterus is not made up of just one or two layers but rather three distinct tissue layers.

5. Which of the following is NOT a mechanism of evolution?

Correct answer: C

Rationale: A) Natural selection is a mechanism of evolution where individuals with advantageous traits are more likely to survive and reproduce, passing on those traits to the next generation. B) Genetic drift is a mechanism of evolution that occurs due to random changes in allele frequencies in a population. C) Lamarckism, also known as the inheritance of acquired characteristics, is a discredited theory that suggests organisms can pass on traits acquired during their lifetime to their offspring. This mechanism has been largely rejected by the scientific community. D) Mutation is a mechanism of evolution that introduces new genetic variation into a population, which can lead to the emergence of new traits and adaptations over time.

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