FREE AP Biology Question and Answers

Question 1

In humans, the Krebs cycle takes place in the

Accepted Answer

mitochondrial matrix

Answer

The Krebs cycle, also known as the citric acid cycle, is a crucial stage of cellular respiration. In eukaryotic cells, including human cells, this metabolic pathway occurs within the mitochondrial matrix, the innermost compartment of the mitochondrion. Here, acetyl-CoA is oxidized to produce ATP, NADH, and FADH2, which are essential for subsequent energy production.

Question 2

One distinction between the two types of cellular reproduction—meiosis and mitosis—is that in meiosis

Accepted Answer

separation of sister chromatids occurs during the second division, whereas in mitosis separation of sister, chromatids occur during the first division

Answer

In mitosis, sister chromatids separate during anaphase, resulting in two identical diploid daughter cells. In contrast, meiosis involves two rounds of division. During meiosis I, homologous chromosomes separate, and then in meiosis II, sister chromatids finally separate, leading to four genetically distinct haploid daughter cells. This two-step separation is a key difference enabling genetic diversity in sexual reproduction.

Question 3

Which of the following DOES NOT describe a bacterial trait?

Accepted Answer

Membrane-bound cellular organelles

Answer

Bacteria are prokaryotic organisms, meaning they lack a nucleus and other membrane-bound organelles such as mitochondria, endoplasmic reticulum, and Golgi apparatus. Their genetic material is located in a nucleoid region, and their cellular functions occur in the cytoplasm. This absence of internal compartmentalization is a defining characteristic distinguishing them from eukaryotic cells.

Question 4

Which of the following statements most accurately describes why a population is referred to as the evolutionary unit?

Accepted Answer

Individuals cannot evolve, but populations can

Answer

Evolution is defined as a change in the heritable characteristics of biological populations over successive generations. While natural selection acts on individuals, affecting their survival and reproduction, it is the population's gene pool that changes over time as advantageous traits become more common. Therefore, individuals do not evolve during their lifetime; rather, the genetic makeup of a population changes across generations.

Question 5

The endocrine system uses a variety of feedback mechanisms to maintain homeostasis. Which of the following best describes favorable criticism?

Accepted Answer

Infant suckling causes a mother's brain to release oxytocin, which in turn stimulates milk production.

Answer

Positive feedback mechanisms amplify an initial stimulus, pushing a physiological process further in the same direction. In the example of milk production, infant suckling stimulates the release of oxytocin, which then causes more milk to be released, leading to more suckling and further oxytocin release. This escalating cycle continues until the baby is full or the stimulus is removed.

AP Practice Test

AP Practice Test

FREE AP Biology Question and Answers