The picture shows a student using a microscope to study a prepared slide of a single-celled organism. A single-celled organism can be classified as a prokaryote based on the absence of —

Different types of mutations can occur in DNA. The diagram represents a type of mutation. Which statement describes the mutation in the diagram?

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?

Part of the cell cycle is shown in this simplified model. This part of the cell cycle is best described as the process that —

Taq polymerase is an enzyme used in the polymerase chain reaction (PCR) to replicate fragments of DNA. A study published in 1976 examined the properties of Taq polymerase after the enzyme was isolated from Thermus aquaticus, a thermophilic bacterium that lives in the hot springs of Yellowstone National Park. The graph shows one of the results of the study. Which statement about enzyme activity is best supported by this graph?

The graph shows the number of taxa of reptiles whose fossilized tracks have been found. Which statement is best supported by these data?

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?

Researchers combined sequences of fruit-fly DNA from a gene for a particular trait with frog DNA. The mixture was heated to separate the DNA strands. Cooling allowed the single strands to form pairs. The researchers observed that some of the fruit-fly DNA paired with frog DNA. The results provide evidence that —

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 —

Some foods that are rich in complex carbohydrates can be difficult to digest. Gas often forms as the foods are slowly digested by bacteria in the large intestine. The advertisement is for a nutritional supplement that prevents intestinal gas. Which of the following represents evidence that could be used to support the claims about this product?

Researchers studying populations of lizards from the genus Gallotia on the Canary Islands compared the protein cytochrome b in different populations. The table shows the number of differences in the cytochrome b protein between different populations. Which conclusion about the relatedness of the lizards do these data support?

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?

Simple leaves have a single leaf on a petiole, or stem, while compound leaves have more than one leaflet on a petiole. This unknown leaf can be identified using the dichotomous key. Which tree does the unknown leaf come from?

In gel electrophoresis a DNA sample from an unknown donor is placed in a small well at one end of a special gel-coated plate. Samples from known donors are placed in other wells on the plate. An electric current is passed through the plate, causing the DNA fragments to separate. The size and location of the separated fragments can be compared for similarities. The more similar the locations and sizes of the fragments, the more closely the donors of the samples are related. The diagram shows four samples being compared with an unknown sample. The donor of which sample is most closely related to the donor of the unknown sample?

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?

The diagram represents a theory about cells. Which theory is represented in this diagram?

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?

The picture shows a contractile vacuole of a unicellular freshwater organism. The contractile vacuole regulates the flow of water into and out of the cell in an aquatic environment. What conditions cause the contractile vacuole to fill with water?

Organisms are classified today using the Linnaean system, and the following table shows the taxonomic classification of two marine organisms living along the Pacific Coast. Taxonomic classification is important to marine biologists because it provides a way to —

Proteins and carbohydrates have many functions in the body of an organism. Specific proteins and carbohydrates perform specific tasks. Information about a protein and a carbohydrate is given below. How are ferritin and glycogen similar in their primary functions for an organism?

A model of a biological process is shown. What is the purpose of this process?

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?

The table shows the survival rate of two types of beetles in the same environment over a period of three years. Which statement about the beetles in this environment is best supported by the data?

Cetaceans are whales and their relatives. The diagram shows some fossils of cetaceans. Which statement provides the best evidence that Ambulocetus natans is an ancestor of Basilosaurus isis?

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?

A student used poster board to construct this model of a section of DNA. Which statement describes this model of DNA?

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

The classifications of four trees are shown in the table. Which two trees are the most closely related?

The arctic fox inhabits northern areas of North America. The same arctic fox is shown in the drawing at different times of the year. What causes this change in fur color?