Wild Soay sheep live in a cold environment on a small Scottish island. The sheep used to be large because they gained extra weight during the summers in order to survive the harsh winters. A recent change in the island’s climate has caused grass to be available for a longer period each year, so survival conditions for the sheep have become less challenging. Researchers who study these sheep have most likely observed a decrease in the wild Soay’s —

The graph below shows the percent of seeds from two plant species that sprout when grown in water containing different amounts of salt. Which of the following best summarizes the effect of saltwater on these plant species?

Which organisms in the food web shown above compete for the same food source in this environment?

The Couch’s spadefoot lives in Texas and has the characteristics listed below. The Couch’s spadefoot is adapted to a certain type of environment. Which of these resources is most likely scarce in this environment?

The Guam rail is a flightless bird found on the island of Guam. It builds a shallow nest on the ground and lays eggs throughout the year. There are no native species of snakes on Guam, so the Guam rail had no experience with snake predators until the brown tree snake was accidentally introduced sometime between 1944 and 1952. These snakes, which eat a wide variety of animal species, quickly established a large population on Guam. How was the Guam rail most likely affected by the introduction of the brown tree snake?

The graph below shows the range of water conditions preferred by three species of fish in an Ozark stream. Water with which of these conditions would cause the most competition for resources among all three species of fish?

Scientists are studying the effects of climate change on the Baltic Sea. Some scientists predict that if current trends continue, the Baltic Sea will become less salty, and it will contain less dissolved oxygen. As a result of these changes, the Baltic Sea will have less biodiversity. The location of the Baltic Sea is shown on the map below. Which statement best explains why biodiversity in the Baltic Sea could decrease if these changes occur?

Barnacles are marine organisms that live attached to surfaces as adults. A scientist studies two barnacle species that live on rocks on a coast in Scotland. In some rocky areas Species A is found alone. In other rocky areas Species B is found alone. In still other rocky areas both species are found together. The diagram below shows the two barnacle species on rocks in their habitats. If Species B were removed from the rocky areas it shares with Species A, Species A would most likely inhabit —

A scientist added bacteria and a nutrient medium that could support the growth of the bacteria to a sterilized petri dish. No other materials were added. The graph models growth of the bacteria over time. Which of these most likely explains why the bacterial population stopped growing?