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?

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?

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

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 G2 stage of the cell cycle?

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?

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?

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?

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?

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?

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?

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?

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?

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

Pepsin and trypsin are two of the digestive enzymes that break down protein. A group of students studied the pH requirements of these enzymes. The graph below shows the results. The students found that pepsin functions best in an acid environment and trypsin functions best in a neutral environment. Based on their observations, pepsin most likely aids in digestion in which part of the human body?

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 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?

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