A scientist investigates the interaction of single-cell pond organisms S and T. He places organism S in pond water in Container 1. He places organism T in pond water in Container 2. He places both organisms in pond water in Container 3. The graphs show how the populations of the organisms in the containers change over time. What can the scientist conclude from this data about the interaction of organisms S and T?

A researcher conducts an experiment with fruit flies. He hypothesizes that the allele for white eyes is dominant to the allele for red eyes. He crosses a red-eyed female with a white-eyed male and repeats this pairing five times. All offspring from these pairs have red eyes.

What should the researcher do after obtaining these results?

A student examines the information in the table. The student conclude that Organism W should be placed at the base of the food web, to represent the feeding relationships in the marine ecosystem. However, the student later learns that Organism W's cells do not contain chloroplasts. What conclusion would be appropriate, based on the new information?

A scientist crosses a homozygous red-eyed fruit fly with a homozygous white-eyed fruit fly. He returns to the lab several days later to record the phenotypes of the offspring in the F1 generation. While collecting his data, the scientist realizes that individuals in the F1 generation have produced an F2 generation of offspring in the same test tube. Which statement explains what the scientist should do next in his experiment?

A student is investigating the effect of temperature on the growth rate of two variations of a plant species. One variation of the plant has broad leaves and the other has narrow leaves. The student prepares to grow several plants of each variation at four different temperatures. She then creates the data table shown to record the height of each plant at the end of the experiment. How can the student BEST improve the validity of the experiment?

A judge allowed a DNA analysis to be entered as evidence in court. Which of the following statements BEST explains why the use of DNA analysis is so effective in establishing identity?

Farmers often spray chemicals on their fields to kill weeds. These chemicals may also harm the crops. Scientists have altered the DNA of some crops so that they will not be harmed by these chemicals. However, some of the weeds can cross-breed with the crops. Which statement describes a negative consequence of altering the DNA of the crops?

Which statement describes the potassium cycle?

Which of the following is a gas that soil bacteria convert into a form that plants can use?

A researcher wants to measure the rate of photosynthesis in two different types of water plants growing in two different aquariums under the same conditions. Which measurement would give the MOST information about the rate of photosynthesis?

The diagram above is an energy pyramid showing the amount of energy available at each trophic level. Each level receives approximately 10% of the energy from the level below. Which of the following statements BEST explains the difference in the amount of energy available at each trophic level?

An ecologist studied a rare bird species within a regional wildlife preserve for several years. The graph shows the data the ecologist collected on the birth rate, death rate, and emigration rate fro the bird species. During which time period did the bird population experience the largest decline?

When a cyclist rides up a steep hill, the cyclist's circulation and breathing rate increase, allowing a greater amount of oxygen to reach the cyclist's muscles. In order to generate energy from this extra oxygen, skeletal muscle contain a greater number of a certain cell part than other tissues. Which of the following cell parts is more numerous in skeletal muscle than on other tissues?

A student uses a microscope to observe cells in the root tissue of an onion. He concludes that the cells are reproducing by mitosis. Which hypothesis is supported by his conclusion?

Carbohydrates are macromolecules used for energy in living organisms. Large carbohydrate molecules are made of smaller building blocks called monosaccharides. The arrangement of which three components is used to distinguish one monosccharide from another?

The diagram shows a particle moving into a cell membrane. Select ALL the lettered (X, Y, Z) particles in the diagram.

The table shows the classification of four animals. According to their classification, which of the following animals are MOST closely related?

Which similarity in two mammals provides the BEST evidence that the mammals are closely related?

The skeletal structures of a crocodile leg and a mouse leg are shown. What can be hypothesized about crocodiles and mice, based on the skeletal anatomy of these two legs?

C. reinhardtii is a species of unicellular green algae that primarily produce energy fro growth through photosynthesis. However, when necessary, they can also produce energy from a carbon source, which allows them to grow in total darkness. A scientist grows a population of these algae in the dark and finds that after 600 generations, the algae population now grows better in the dark than in the light. Which statement BEST explains what has happened to the cells in the algae population?

The table shows which mRNA codons code for various amino acids. Which amino acid sequence will be produced by translation of the mRNA sequence UAC UCU ACC?

In pea plants, the allele for red flowers (R) is dominant, and the allele fro white flowers (r) recessive. The Punnett square shows the cross of two pea plants, each with red flowers. According to the Punnet square, what percent of the offspring resulting from the this cross will have red flowers?

A type of rodent can have white or brown fur. The allele for white fur is recessive to the allele for brown fur. What is the genotype of an individual with white fur?

A female carrier of colorblindness and a male who is not colorblind produce a son. Given the fact that colorblindness is a recessive X-linked trait, what is the chance that the son will be colorblind?