A scientist has been tracking and studying a population of deer in Yellowstone National Park. He surveys the population every six months. Usually, the population is thriving and has a gene pool with a wide variety of traits. But during one six-month period, an event occurred that affected the population, and when the scientist returned, the amount of genetic variation had decreased significantly. Which of the following is most likely the event that occurred to change the population? Yellowstone National Park expanded its borders. A population of wolves was introduced into Yellowstone National Park. The amount of disease in the deer population decreased. More grass and shrubs were planted in Yellowstone National Park.

Explanation:

Let's evaluate each choice. Remember we are looking for an event to decrease the genetic variation and population.

A. Yellowstone expanded its borders

If the park expanded, it's likely the population would increase. There would be more space and resources for the deer.

B. A population of wolves was introduced

A wolf is a predator that preys on deer. If they were introduced, they would use the deer as a food source and decrease the population.

B seems like a good answer, but let's check the others.

C. The amount of disease in the deer population decreased.

This would help the deer population. Less disease means fewer deaths and a greater population.

D. More grass and shrubs were planted in Yellowstone

Deer are herbivores, so grass and shrubs would provide more food. This would keep the deer nourished and healthy, meaning a greater population.

The best answer choice is B: A population of wolves was introduced into Yellowstone National Park

Environmental science studies the interactions between the physical, chemical, and biological components of the environment, including their effects on all types of organisms. earth science (also known as geoscience), is an inclusive term for all sciences related to earth (geology, meteorology, oceanogr maphy, etc).  although environmental and earth science cover essentially the same material, environmental science places greater emphasis on the biological realm, while earth science places greater emphasis on the physical realm.    environmental and earth science study the interactions of four major systems or “spheres” (figure 8.6).  the  geosphere  consists of the core, mantle and crust of the earth.the  atmosphere  contains all of the earth’s air and is divided into troposphere, stratosphere, mesosphere, thermosphere and ionosphere.the  hydrosphere  contains all of the solid, liquid and gaseous water on earth, extending from the depths of the sea to the upper reaches of the troposphere where water is found.  ninety-seven percent of the hydrosphere is found in salty oceans, and the remainder is found as vapor or droplets in the atmosphere and as liquid in ground water, lakes, rivers, glaciers and snowfields.  the  biosphere  is the collection of all earth’s life forms, distributed in major life zones known as biomes:   tundra, boreal forest, temperate deciduous forest, temperate grassland, desert, savannah, tropical rainforest, chaparral, freshwater, and marine.although the four systems have their unique identities, there is substantial interaction between them.  environmental scientists study the effects of events in one sphere on the other spheres. for example, a volcanic eruption in the geosphere may cause profound direct and indirect effects on the hydrosphere, atmosphere and biosphere as follows: example 1 (volcano)    on may 18, 1980, mount saint helens, in the state of washington, erupted.  this event altered the surrounding environment, and provided scientists with an opportunity to study the effects of volcanic eruptions on the geosphere, hydrosphere, atmosphere and biosphere.  such studies are vital because volcanic eruptions will continue to occur, and will have increasing impact on humans as people continue to settle lands closer to dormant volcanoes. the following are but a few of the myriad of interactions resulting from a volcanic