A student is studying the ecology of a playa lake, which forms after a rainfall in a dry lake bed. The table lists the organisms that the student observed. Which level of biological organization has the student described in the table?

Some students are instructed to put a celery stalk in a red dye solution for a lab activity. First the students carefully cut the bottom of the stalk with a scalpel. Then they put the stalk in a beaker with the solution and place the beaker on a shelf in the lab room. The next day they check the stalk and make observations. The students note that the leaves at the end of the stalk have changed color from green to red. The students cut across the celery stalk and use a hand lens to see that the small tube openings along the edge of the celery stalk are also red. The cross section is shown here. How do the plant systems work together to make this movement of liquid possible?

Lactose is found in milk products. It is converted by the body into a usable form in a series of chemical reactions. The diagram shows the series of reactions that convert lactose into a usable form.

Toxoplasmosis is an infection producing brain lesions caused by the parasitic protozoan Toxoplasma gondii. Mice with their gonads removed are more resistant to T. gondii and develop very few lesions on their brain tissue. The graph shows the results of a scientific study of normal adult mice infected with T. gondii. Which systems most likely interact and cause the severity of infections to vary?

An animal can wound a tree by scratching away the bark. The tree can respond to the wound in many ways. Usually sap quickly covers the wound, and then the tree covers the wound with new growth. The diagram shows a cross section of a tree with a healed wound. What process worked most directly with the transport system to heal the wound?

Most plant leaves take in more carbon dioxide as light increases. They give off carbon dioxide if light intensity is too low. The graph shows a plant’s carbon dioxide levels at different light intensities. At point X, the rate of which process is equal to the rate of photosynthesis?

Pepsin and trypsin are two of the digestive enzymes that break down protein. A group of students studied the pH requirements of these enzymes. The graph below shows the results. The students found that pepsin functions best in an acid environment and trypsin functions best in a neutral environment. Based on their observations, pepsin most likely aids in digestion in which part of the human body?

An informational pamphlet in a health clinic describes an interaction between body systems. Which statement identifies the body systems that are directly involved in the interaction described and explains how they accomplish the interaction?

Structures represented in the illustration below are found in the lower epidermis of a plant leaf. The illustration at right shows the response to a certain environmental condition. The response represented in the illustration would most likely be caused by —

The diagram shows the internal feedback mechanism that maintains blood-calcium (Ca2+) homeostasis. If a person has a blood-calcium (Ca2+) level of 8 mg/100 mL of blood, which of the following mechanisms does the body use to maintain blood-calcium homeostasis?

The diagram shows the reproductive system of a plant. Which of the following best describes the interaction that occurs between a plant’s reproductive parts during self-fertilization?

The diagram represents one way an enzyme can be inhibited. Which statement explains the effect of an inhibitor on an enzyme?

The graph models core body temperature during a rapid change in environmental conditions. Which statement explains the pattern in the graph?

The table shows some observations made by four students during a field trip to a nature area. Which student made observations of a community of organisms?

Plants called sundews have rounded green leaves with many hair-like structures. The ends of these structures contain enzymes in a sticky liquid that looks like nectar or moisture, as shown in the picture. The hairs do not react to dust or nonliving material but will bend inward when insects get caught in the sticky liquid. Sundews digest trapped insects over a period of a few days. Based on this information, what functions do the specialized leaves of sundews perform?