A remora is a fish that has an adhesive disk on the back of its head that it uses to attach itself to a large shark. When food floats away from the shark’s mouth as it feeds, the remora collects the scraps. Drawings of a shark with a remora attached and a remora’s adhesive disk are shown below. The relationship between the remora and the shark is an example of —

The picture shows a pika, a small mammal found in grassland ecosystems. The vast grasslands of the Tibetan plateau are home to the plateau pika. The numerous pikas are prey for many predators of the grasslands, which serve as a major watershed for much of the area. The watershed drains large quantities of groundwater during the rainy season, or the monsoon season. Pikas have extensive burrows that help drain groundwater rapidly and are used as nesting sites by many bird species. However, many people advocate the eradication of the plateau pikas because they compete with livestock for grass. Which of these will most likely happen if the plateau pikas are completely removed from the Tibetan plateau grasslands?

The picture shows bean-shaped glands called nodes. The clusters of cells in nodes include macrophages that break down viruses and other potentially harmful materials. Nodes also contain cells that produce protein particles capable of capturing harmful materials that flow in tissue fluid through the nodes. Different parts of the body are drained by nodes in different regions of the body. Which body systems are directly responsible for regulating these nodes and protecting the body from harmful materials in tissue fluid?

This diagram demonstrates why the ocean is a large carbon sink. An increase in the amount of carbon dioxide in the atmosphere can cause atmospheric temperatures to increase. Which statement explains how this could affect the ocean as a carbon sink?

The diagram demonstrates a feedback process involving antidiuretic hormone (ADH). ADH increases the permeability of parts of the nephrons of the kidney, resulting in less water in the urine. This feedback loop is likely to be activated when —

The energy pyramid below shows the energy made available by producers. Based on the energy flow between trophic levels in an energy pyramid, how much energy would be expected to be found at the secondary consumer level in this pyramid?

A student reads this advertisement for a product containing a plant micronutrient that can be added to soil. Based on this information, the student can conclude that boron is absorbed by plant roots from soil and then —

A student researching bacteria concluded a report with the claim in the box. Which statement correctly addresses the validity of the claim?

Four common relationships between organisms are listed in the box. Which statements best describe these relationships?

A student conducted an investigation to study phototropism in grasses. The only difference between the control group and the experimental group was light conditions. The control group was provided full light, while the experimental group was shaded on one side. The diagrams show the average heights and positions of blades of grass in the investigation. Which statement best explains why the grass tips of the experimental group bent toward the light?

Scientists conducted an investigation to study the possible effects of air pollution on chlorophyll a and chlorophyll b in plants. The scientists gathered plants from polluted areas and unpolluted areas and then measured the presence of chlorophyll in 50 mg of plant leaves. The results are shown in the graph. Which inference do these data support?

A student studying interactions between body systems constructs this table. The student plans to fill out the table with phrases that describe an interaction between each pair of systems. Which of these phrases could be placed in the position marked with an X?

The diagram shows a partial East Texas food web. Which table correctly classifies these organisms?

The amount of energy the producers in this energy pyramid provide the primary consumers is 54,000 joules. From this amount, 540 joules are provided to the tertiary consumers. Based on this model, how much of the energy was provided to secondary consumers?

Food webs such as the one shown were first used in 1927 by the animal ecologist Charles Elton. The food web below represents the feeding relationships among organisms in an Alaskan ecosystem. An environmental change that removed which of these organisms from the ecosystem would cause the most instability in the ecosystem?

The photograph shows monarch butterflies landing on plants where there are thousands of other monarch butterflies. These butterflies feed on milkweed plants as they travel south for the winter, covering distances of 5,000 km or more each year. However, the population of these butterflies has been steadily declining over the last 20 years. What is the most likely reason the population of these butterflies has been declining?

Health professionals sometimes recommend nutritional supplements that contain a variety of species of bacteria to promote good digestive health. The product label for one of these supplements is shown. Why does this type of bacteria-filled supplement benefit human health instead of causing illness?

Some relationships between different organisms are shown in the table. Which table correctly identifies each type of interaction described?

Part of a hydrothermal vent food web is represented in the diagram. Which organisms are both secondary and tertiary consumers in this food web?

Several structures work together to allow flowering plants to reproduce. The diagram shows a typical flower. Which table correctly identifies the function of each structure or group of structures in the reproduction of the plant?

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?

On March 24, 1989, an oil tanker ran aground on Bligh Reef in Prince William Sound, Alaska, and spilled millions of liters of crude oil. The graph shows pink salmon populations in Prince William Sound from 1970 to 1999. What do these data suggest about the effect the oil spill had on pink salmon?

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?

The mimosa plant displays thigmotropism by collapsing its leaves in response to touch, as shown in the pictures below. The plant on the left is undisturbed. The upper stem of the plant on the right has been touched. What is the most likely benefit of this mechanism for the plant?

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 food web shows the flow of energy through a sagebrush-steppe ecosystem. Which of these organisms are in a trophic level that receives a larger percentage of the energy captured by the producers than the percentage received at the bats’ trophic level?

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 shows the flow of organic molecules through an ecosystem. One process that occurs in this ecosystem is labeled X, and another process that occurs is labeled Y. Which two processes are identified by the labels X and Y?

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 the 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 below. How do the plant systems work together to make this movement of liquid possible?

The table below provides some information about the feeding methods of the five rhinoceros species. Which rhinoceros species is best adapted for feeding in the large open grasslands of Africa’s Serengeti ecosystem?

A marine ecosystem is represented below. What is lost to the environment at each of the trophic levels of this ecosystem?

The osmoregulation process is shown below. This process is an example of which of the following?

In any environment or ecosystem, organisms can have several different types of relationships. Three types of relationships are described below. Which of these correctly describes the relationships between the organisms?

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?

Brazil nuts (Bertholletia excelsa) are tall canopy trees that make up a large portion of the Amazon rain forest. They produce large grapefruit-sized seedpods. The agouti, a grounddwelling rodent, has teeth strong enough to open the tough seedpods. While the agouti eats some of the tree’s seeds, it also buries caches in various spots on the rain forest floor. Why is the agouti important to the rain forest ecosystem?

A terrestrial food web is shown below. Which of the following lists only organisms that are secondary consumers in this food web?

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?

The diagram below represents the nitrogen cycle in a student’s aquarium. Ammonia, nitrites, and, to a lesser degree, nitrates can be harmful to fish. The student wants to keep the nitrogen in this aquarium cycling normally without having to continually change the water. Which of the following should the student add more of to help remove nitrates and improve the natural cycling of nitrogen in this aquarium?

Amphibians are dying in large numbers after being infected by an aquatic fungus called Batrachochytrium dendrobatidis. The origin of this fungus is unknown, but scientists suspect that humans are helping spread it. More than 350 amphibian species have been affected, and at least 200 species of frogs have suffered serious reductions in population or become extinct. The map below shows the worldwide distribution of B. dendrobatidis. What will be the most likely impact of the decline in frog populations resulting from the fungal infection?

The graph below shows the changes in the number of species in an ecosystem. Which event was most likely the cause of the changes in species diversity in this ecosystem?

Surtsey is an island located south of Iceland. The island was formed by a volcanic eruption and first appeared in 1963. The table below contains descriptions of changes in the population and diversity of species on Surtsey. Which of these lists the descriptions in the correct order of ecological succession on Surtsey?

Which of the following are missing from the food web shown above?

The acacia ant (Pseudomyrmex ferruginea) lives in the bullshorn acacia plant, as shown below. The acacia ant nests and feeds in the plant’s hollow thorns. The ant helps protect the bullshorn acacia by attacking insects and grazing animals that come near the plant. The relationship between the acacia ant and the bullshorn acacia is an example of which of the following?

The carbon cycle includes processes that release carbon into the atmosphere and places that act as carbon reservoirs. The diagram below shows both major processes that release carbon and major carbon reservoirs. Which of these disruptions would cause an excess output in the carbon cycle?

The Nile River flows into the Mediterranean Sea. The Aswan High Dam contains the flow of water from the river and reduces the annual fall flooding. The floodwater is trapped behind the huge dam, allowing irrigation for agriculture. Sediments that would be washed away by the annual floods are also trapped behind the dam. The graph shows the water flow from the Nile that enters the Mediterranean Sea. How has this dam most likely affected the Mediterranean Sea ecosystem?

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?

The Texas blind salamander (Eurycea rathbuni) lives in the Edwards Aquifer region around San Marcos. Along with other species the salamander lives in total darkness in the underground crevices and caves of the aquifer region. The table lists some of the organisms that live in this environment and their food sources. In an energy pyramid for these aquifer cave dwellers, which of the following would be placed at the bottom?

The graph shows the basic changes in a forest community after a disturbance occurred. The information shown in the graph suggests that the changes in the forest community were caused by —

Plant roots have extensions called root hairs. These root hairs are important in the homeostasis of the plant. Which statement best explains the importance of the root hairs to the stems and leaves of the plant?

The table lists some organisms found in a swamp ecosystem and their sources of energy. When constructing an energy pyramid of the swamp ecosystem, which of these would be placed at the top of the pyramid?

A corn plant produces both male and female flowers. The male flower forms the tassel and the female flower forms the ear of corn. The silks that emerge from the ear are the stigma of the female flower. Each silk leads to an ovule that can become a corn seed. Which of these must happen for corn seeds to develop on the ear?

Enchanted Rock State Natural Area is located in Central Texas. Enchanted Rock is a dome of granite. The area contains four easily identifiable communities. The table describes characteristics of each type of community in the area. A student studying primary succession should focus on which of these communities?

A partial meadow food web is shown. Based on this food web, which organisms are direct sources of energy for secondary consumers?