The cladogram shows the evolution of land plants as indicated by fossil records. Which discovery would challenge the validity of this cladogram?

Atherosclerosis is a disease that obstructs blood flow and, therefore, oxygen supply to target organs. A major component of atherosclerosis is the excessive reproduction of smooth muscle cells of the blood vessels. Certain drugs may have the potential to reverse or prevent the unregulated reproduction of the diseased blood-vessel cells. Which of these processes is the most likely target of these drugs?

Carbohydrates are more easily metabolized than lipids. However, on a gram-for-gram basis lipids provide cells with more —

Lord Howe Island is a volcanic island in the Tasman Sea that is about 11 km long and 2.8 km wide. The island has two species of palm trees, Howea forsteriana and the more abundant Howea belmoreana. The two species do not interbreed even when they grow very close to each other. Which evolutionary process fails to occur?

Using a light microscope, a student identified the following characteristics of four organisms found in a sample of pond water. Based on the observations of the student, which organisms most likely belong to the taxonomic group for bacteria?

Sexual reproduction in animals depends on the production of gametes. Which of these processes produces gametes in animals?

Some fungi secrete substances that are toxic to bacteria that compete with them for food. Scientists have used their knowledge of this ability of fungi in order to produce which of the following substances?

The sequence of nitrogenous bases in DNA varies widely. The sequence of the bases in DNA is most important for which of the following?

Four different types of cells are shown below. Which characteristic is shared by all four cells?

Checkpoints occur between the stages of the cell cycle. If a cell does not meet certain criteria at the end of a stage, it will not move to the next stage. Which of these occurs just before the cell enters the G stage of the cell cycle?

In the 1860s Gregor Mendel performed numerous dihybrid crosses between pea plants. Dihybrid crosses involve the study of the inheritance patterns related to two different traits. In guinea pigs the allele for black fur (B) is dominant over the allele for brown fur (b), and the allele for short fur (F) is dominant over the allele for long fur (f). What percentage of the offspring from a BbFf x bbff cross would be expected to be heterozygous for both traits?

Which group of organelles is directly responsible for the production of new molecules within a cell?

In 1917 the biologist Thomas Hunt Morgan conducted studies in which he kept some caterpillars in the dark and placed some others under red, green, or blue lights. Exposure to red light produced butterflies with brightly colored wings. Exposure to green light resulted in dark-colored wings. Exposure to blue light or no light resulted in pale-colored wings. What was the most likely conclusion of Morgan’s research?

Severe acute respiratory syndrome (SARS) is an illness caused by a coronavirus. Symptoms including a high fever, headaches, and body aches typically occur two to seven days after infection by the virus. SARS is more serious in elderly patients. This information suggests that the reproductive cycle of the SARS virus is —

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. If Enzyme 2 is denatured, the levels of which substance will increase?

The picture below shows a person’s karyotype. Which of the following can best be determined by examining this karyotype?

The cellular process known as the sodium-potassium pump was discovered in the 1950s by Jens Christian Skou, a Danish scientist. This process is a form of active transport that moves three sodium ions to the outside of a cell for every two potassium ions that it moves into the cell. Which of these best explains why energy is needed for active transport?

Researchers Robert Briggs and Thomas King used ultraviolet radiation to destroy the nuclear DNA of frog eggs. Nuclei from adult skin cells and from tadpole-gut epithelial cells were cultured and then injected into eggs that had their nuclei destroyed. The results were tadpoles. Which conclusion is supported by the data from this investigation?

The Linnaean taxonomic system classifies organisms into divisions called taxa. If two organisms belong to the same taxonomic group, they are related. Similarity at which of these levels indicates the closest relationship?

Sickle-shaped red blood cells result from a mutation in the gene that codes for hemoglobin. This mutation results in sickle-cell anemia. A partial sequence of bases from a normal hemoglobin gene and a sequence that results in sickle-cell anemia are shown below. What type of mutation is depicted in this sequence?

In Madagascar scientists have discovered a moth, Xanthopan morganii praedicta, that has a 30.5 cm proboscis and feeds from and pollinates Darwin’s orchid, Angraecum sesquipedale. The orchid has a nectar-producing tube that is 27.9 cm long. How is the moth’s proboscis size an adaptation for its environment?

Genome maps provide the DNA sequences of chromosomes. Some scientists have compared the genome maps of a hedgehog and a sloth. What do these genome maps allow the scientists to determine?

Tomato plants usually have hairy stems. Hairless stems are present in tomato plants that are homozygous recessive for this trait. If the stem characteristics are determined by a single gene, what is the expected outcome of crossing two tomato plants that are heterozygous for hairy stems?

Which of the following biomolecules typically contains both nitrogen and phosphate?

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?

Telophase is a stage of a cellular process that begins after the chromosomes have moved to opposite poles of the cell. During which cellular process does telophase occur?

Which of the following polypeptides is coded for by the mRNA sequence ′ ′ 5 AUGGUUAAACGACAAUCC3?

Which condition is essential for natural selection to result in a new species?

In 1952 Rosalind Franklin took the x-ray photograph shown below, which gave the world its first look at DNA. By studying this photograph, scientists gained knowledge about the —

The diagram shows a dichotomous key and a picture of a fruit. According to the key, the fruit comes from which species of tree?

The opossum, which is native to North America, and the kangaroo, which is native to Australia, are marsupials. The fact that both these mammals incubate their immature offspring in a pouch provides

evidence that they —

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?

The cladogram shows the evolution of land plants as indicated by fossil records. Which discovery would challenge the validity of this cladogram?

The outermost layer of plant stems in dicotyledons consists of epidermal cells and guard cells that surround openings called stomata. The epidermal cells are usually covered with

a waterproof layer that provides protection from injury and water loss. The stomata allow gas exchange. The epidermal cells and stomata have functions similar to those of which two human body systems?

Dead zones are low-oxygen areas that develop on the seafloor. Scientists hypothesize that phytoplankton blooms cause these dead zones. Phytoplankton blooms occur when excess nutrients are introduced by pollution from fertilizers, sewage plants, and the burning of fossil fuels. Which of the following would most likely cause an increase in these contributors to dead zones?

What two human systems work together to provide body cells with a constant supply of oxygen while removing carbon dioxide waste products?

Some fungi secrete substances that are toxic to bacteria that compete with them for food. Scientists have used their knowledge of this ability of fungi in order to produce which of the following substances?

A person infected with the human immunodeficiency virus (HIV) may not have any symptoms for a period of time. During this period the virus affects the body by doing which of the following?

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

Which of the following functions at the same organizational level as the kidney in the human excretory system?

Scientists estimate that there are more than 20,000 species of ants. The species range in size from 1 mm long to 38 mm long and live in most environments. The diets of ants range from flowers and seeds to fluids from their own larvae. Ants have been able to successfully inhabit so many different environments because their populations have been able to —

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?

Hydrothermal vents form deep in the ocean when iron-rich magma is released from openings on the seafloor. These vents spew extremely hot water (400°C) mixed with methane and sulfur. Bacteria that thrive in this hostile environment form the base of a food chain that leads to colonization by tube worms, mussels, and many other life-forms. When a hydrothermal vent becomes inactive and cold, the bacterial community that lives in the hot fluid methane and sulfur dies out. Which organisms most likely succeed the original community in this ecosystem?

When a person is suddenly cut by a sharp object, a nervous impulse is sent along a sensory neuron to the spinal cord. The impulse is immediately transmitted through motor neurons to produce a response. Which of the following correctly identifies and describes this response?

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 ground-dwelling 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?

The Linnaean taxonomic system classifies organisms into divisions called taxa. If two organisms belong to the same taxonomic group, they are related. Similarity at which of these levels indicates the closest relationship?

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?

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?