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A myocardial infarction (heart attack) results from a blockage in which of the following blood vessels of the heart?
Which of the following skin layers contains stem cells that produce new cells which migrate to the skin surface over time?
In the following balanced chemical equation, how many oxygen atoms are present on each side of the reaction? 2 C2H6 + 25 O2 → 16 CO2 + 18 H2O
How many electrons are found in a neutral boron atom with an atomic number of 5 and a mass number of 11?
A researcher is comparing the surface areas of the following cells under a microscope: a red blood cell, a neuron, a muscle cell, and a bacterial cell. Which of these cells is likely to have the smallest surface area?
A patient goes to the doctor with a cold and sore throat and asks for antibiotics. The doctor refuses to prescribe antibiotics because the illness is caused by which of the following pathogens?
Under a microscope, which of the following is most likely to be seen if the microbe being examined is a fungus?
A researcher wants to gather data on the average wing strength of all birds found in the American Northwest. The researcher only had one small net, so all large birds were excluded from the study. The researcher's results were different than expected, but he believes his data include enough birds to estimate the wing strength of all birds. For which of the following reasons should this data be rejected?
Vidya mailed a letter on his way home from work, but as he neared home, he realized he had forgotten to turn around to go back and get it. Which of the following actions did Vidya take before mailing his letter?
Which of the following enzymes begins the digestion of polysaccharides into simpler sugars?
Glycerophospholipids are a class of chemicals known as "amphipathic" because they contain sections that are both hydrophilic and hydrophobic. Which portion of a glycerophospholipid accounts for its hydrophilic character?
Which of the following observations refutes the hypothesis that characteristics acquired during a parent's lifetime are inherited by its offspring (i.e., refutes Lamarckian inheritance of acquired traits)?
The following information must be communicated in a general newspaper article: "Most living animal species belong to the infrakingdom Bilateria, a highly proliferative clade whose members have a bilaterally symmetric body plan. The vast majority belong to two large superphyla: the protostomes, which include organisms such as the arthropods, mollusks, flatworms, annelids, and nematodes; and the deuterostomes, which include the echinoderms, hemichordates, and chordates, the latter of which contains the vertebrates." Which of the following types of graphs should the editor use to best present this information and show the hierarchical relationships and overlap between the different organism groups?
A DNA strand has the sequence 5'-A-C-A-G-C-C-G-T-A-A-A-3'. Which of the following is the sequence of its complementary strand?
An increase in which of the following would lead to a decrease in the amount of oxygen in the blood?
Consider the following reaction, which is a critical part of lipid metabolism: triglycerides + water → glycerol + fatty acids, catalyzed by lipase. Which of the following best explains the role of lipase in this reaction?
A scientist collects data from egg samples taken from chickens that were fed different diets (Diet A and Diet B). Assuming the eggs are the same size, which of the following can be inferred from the data regarding the protein content of the eggs?
Consider the chemical formula below. Which of the following statements correctly describes the composition of this compound? Ca2SO4
Which of the following summarizes a change that takes place as a solid turns into a liquid?
When you think of a hummingbird, you most likely think of a very small creature with rapidly beating wings. No surprise that the hummingbird family contains the smallest bird in the world. Somewhat more surprising is the fact that there are more than 400 kinds of hummingbirds, 19 of which are found in the United States. It turns out that plenty of diversity can be packed into small bodies; one thing all hummingbirds have in common is their ability to amaze. The smallest hummingbird is no longer than an adult bumblebee; the largest, the giant hummingbird, grows from 8 to 9 inches in length. Despite their diminutive stature, these birds can do many incredible things. They are the only birds that can fly backward. Their wings beat faster than those of any other bird, from 60 to 70 times per second. In the eastern United States, the ruby-throated hummingbird is the only kind commonly found north of Florida. While both male and female have a coat of brilliant metallic green, only the male has a bright red throat. The male is very aggressive in defending food sources, often taking on enemies much larger than himself. A mature ruby-throated hummingbird is only about 3 to 4 inches long. When newly hatched, three of the birds can fit inside a nest the size of a large thimble. The birds eat insects and extract nectar from flowers for their diet. Many people hang hummingbird feeders containing sugar water, and hummingbirds flock to them. Feeders are an important supplement to their natural diet. Although they weigh as little as a penny, they have long migration routes to follow in spring and fall. They are marvels of speed, agility, and beauty. Which of the following has a similar theme to the hummingbird passage?