Invasive plant species affect the interactions of living and nonliving components of an ecosystem, so the removal of invasive plants is often necessary. The goal of most plant-control methods is to disrupt or inhibit the function of different plant systems. For example, insects can be used to chew through roots in order to reduce a plant’s ability to absorb water. Which of these functions would be most immediately affected by a reduction in water uptake by roots?

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?

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 human immunodeficiency virus (HIV) often infects and destroys CD4 T cells. These CD4 T cells are one of many kinds of white blood cells that are an important part of the immune system. The most common danger related to the destruction of CD4 T cells is —

Common baboons live on the savanna in breeding groups called troops. While females tend to stay with the troop, younger or less dominant males may leave to join a neighboring troop. Which of these is a likely outcome of movement by young males?

An estuary collects sediments from the ocean and rivers that feed into it. The sediments swirl around and then settle to form a mudflat. Eel grass is then established on the mudflat. The ecosystem changes over time and ultimately develops into a salt marsh that contains mangrove trees. Which of the following is likely NOT involved in this example of ecological succession?

Differences in traits such as hair texture are determined by differences in —

Which molecule synthesized by plants is a major source of energy for cellular processes in both plants and animals?

From a single fertilized ovum undergoing a series of rapid cell divisions, a human infant develops. The embryonic cells become specialized for a variety of functions. Which of these statements best describes how different cell types develop?

In the 1940s, the scientist J. B. S. Haldane linked many human red blood cell disorders with the tropical regions where malaria occurs. Haldane hypothesized that the widespread presence of these red blood cell disorders as well as traits that protect individuals from malaria were the result of natural selection. Haldane’s hypothesis was later confirmed by the research of A. C. Allison. The resistance to malaria carried by individuals in areas where malaria is widespread is the result of —

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 surface of the stomach is lined with epithelial cells called surface mucous cells. These cells produce a thick mucus that coats the epithelium on the inside surface of the stomach. What is the purpose of the mucous coating?

In Holstein cattle the allele for black hair color (B) is dominant over the allele for red hair color (b) , and the allele for polled (P), or lacking horns, is dominant over the allele for having horns (p). What is the expected phenotypic ratio of the offspring of a BbPp × BbPp cross if these alleles sort independently?

Which of the following is an example of the endocrine system directly interacting with the nervous system?

Roads are often built through forests for industrial purposes or as land is developed for residential and commercial needs. How would road construction through a forest most likely affect the ecosystem?

People who have leukemia, a cancer that affects white blood cells, are often given Cytarabine. This drug inhibits the synthesis of DNA. Which phase of the cell cycle is most affected by Cytarabine?

Recent studies in bone research indicate that using ultrasound on a broken bone can decrease the healing time by 25%. Which of these are the most basic levels of organization involved when a bone heals?

Which of these is the direct result of an error in the transcription of a DNA nucleotide?

The rocky material left behind by a retreating glacier forms what is called a moraine. When primary succession occurs on a moraine, which life-forms will help create the soil by breaking down bare rock?

Viruses can be transmitted through air, water, food, insect bites, and direct skin contact. Once a virus gains entry to the body, it invades a host cell in order to —

Photosynthesis and cellular respiration both involve the use and release of gases. Which statement correctly identifies the role of gases in the two processes?