The graph shows how fast catalase broke down hydrogen peroxide at six temperatures in degrees Celsius. Which statement best explains why the rate falls sharply above 37 degrees Celsius?

One strand of a DNA molecule reads T-A-C-G-G-A. What is the sequence of the complementary DNA strand?

A field is sprayed with the same pesticide every year. After ten years the spray barely reduces the insect population at all. What best explains the change?

Only about 10 percent of the energy stored at one trophic level is stored at the next level up. What becomes of the rest?

A student tests an unknown food sample and finds it is built mainly from long chains of amino acids. Which macromolecule makes up the sample?

In a human liver cell, where is a messenger RNA molecule assembled, and where is it read to build a protein?

The forelimb of a whale, a bat and a human contains the same set of bones arranged in the same order, although the limbs do very different jobs. What does this best support?

Use the food web. A disease removes almost every shrew from this grassland. What is the most likely immediate effect on the grasshopper population?

Potato cores of equal mass were left for 30 minutes in sucrose solutions of different concentrations. In which solution was the solute concentration closest to that inside the potato cells?

In pea plants, tall (T) is dominant to short (t). The square shows a cross between a heterozygous tall plant and a short plant. What fraction of the offspring is expected to be short?

Which statement about evolution by natural selection is accurate?

Barnacles fixed to a whale's skin are carried to rich feeding grounds where they filter food from the water. The whale is neither helped nor harmed. Which relationship is this?

Look at the plant cell. Which numbered structure captures light energy and uses it to build glucose?

A single base is deleted near the beginning of a gene. Why does this usually damage the resulting protein more than the substitution of one base at the same place?

The lion is named Panthera leo. What does the first word of that name tell a biologist?

A deer herd on an island grows quickly for several years, then levels off and stays near 500 animals for a decade. What does the value 500 represent?

Cells lining the human intestine take glucose in from the gut even when glucose is already more concentrated inside the cell than outside. What does the cell need in order to do this?

One cell in an ovary or testis goes through meiosis and produces four cells. How do those four cells compare with the cell that started the process?

Use the cladogram. Which two organisms share the most recent common ancestor?

A lava flow cools into bare rock. Lichens colonize it first, then mosses build up soil, and shrubs follow decades later. What is this sequence called?

Which statement correctly compares the overall equations for photosynthesis and aerobic cellular respiration?

In one cat population the allele for a short tail is dominant, yet most cats in that population have long tails. How is this possible?

Into which three domains do biologists sort all living things?

The diagram traces carbon through an ecosystem. Which process moves carbon from the first stage into the second stage?

A healthy green plant is sealed in a clear jar. During the night the carbon dioxide inside the jar rises steadily. Why?

In guinea pigs, black coat (B) is dominant to white (b). Two heterozygous black guinea pigs are crossed. One cell of the square is hidden. Which genotype belongs in that cell?

Fossils of horse ancestors collected across 50 million years show a steady change in leg bones and tooth shape. Which conclusion do these fossils best support?

Bacteria in the root nodules of a bean plant convert nitrogen gas into ammonium compounds. Why does the plant depend on this step?

A tumor develops when cells keep dividing even though the signals that should stop division are present. Which part of the cell cycle has failed?

A red snapdragon crossed with a white snapdragon produces offspring that are all pink. What pattern of inheritance does this result show?

A river changes course and splits one squirrel population into two. After thousands of generations the two groups can no longer interbreed. What has taken place?

Removing a top predator from a food web affects only the animals that predator ate.

A sprig of Elodea was lit with four colors of light of equal intensity and the oxygen bubbles it released were counted. Which conclusion does the graph support?

Bacteria given the human gene for insulin go on to make working human insulin. What does this result show about the genetic code?

A human muscle cell contains far more mitochondria than a skin cell of the same size. What does that difference suggest about the muscle cell?

Look at generation I and their daughter II-1 in the pedigree. What does the chart show about the allele for this trait?

Photosynthesis and cellular respiration both take place in the cells of a green plant.

Hemophilia is an X-linked recessive condition. Why does it appear far more often in males than in females?

Schleiden and Schwann concluded that plants and animals are built from cells. Which observation did Rudolf Virchow later add to complete the cell theory?

A person's skin cells and liver cells contain the same DNA sequence.