Standard: HS-LS2-6.

Evaluate claims, evidence, and reasoning that the complex interactions in ecosystems maintain relatively consistent numbers and types of organisms

A Shifting Balance in Meadow Valley

In Meadow Valley, a diverse array of plant and animal species form a complex web of interactions. The ecosystem features tall grasses, wildflowers, and shrubs that provide food and shelter for insects, small mammals, and birds. Among these species, rabbits and field mice are prominent herbivores, feeding primarily on grasses and flowering plants. Hawks and owls, in turn, prey on the rabbits and mice, helping to regulate their populations.

Recently, the population of coyotes in Meadow Valley has increased. This has led to noticeable changes in the behavior and population sizes of other organisms. As coyotes hunt for rabbits and small mammals, some species have altered their activity patterns, becoming more nocturnal to avoid predation. The presence of more coyotes has also affected the behavior of hawks and owls, who now face increased competition for food sources.

During the past few years, a new plant species known as thornbrush has started to spread across the valley. Thornbrush grows quickly and outcompetes native grasses and wildflowers for sunlight and soil nutrients. The dense nature of the thornbrush makes it difficult for some herbivores to move through the area, and its sharp thorns deter many species from grazing on it.

Insects, however, have adapted to this new plant. Certain beetles feed on thornbrush leaves, and some caterpillars have developed the ability to consume its tough, fibrous stems. These insects have become an important food source for birds such as sparrows and wrens, which rely on them during the spring and summer months.

The spread of thornbrush has led to changes in the local food web. With fewer grasses and wildflowers available, rabbits and field mice have had to adjust their diets and territories. Some of these herbivores have begun to venture further into the forest on the edge of the valley, seeking alternative food sources. This shift has, in turn, affected the distribution of hawks, owls, and other predators that follow their prey.

Ecologists studying Meadow Valley have also noted changes in the interactions among plant species. The rapid growth of thornbrush has led to a decline in native wildflowers that once supported a wide range of pollinators, including bees and butterflies. As these pollinators become less common, plants that rely on them for reproduction may struggle to survive, which could further alter the valley’s plant community.

The increasing dominance of thornbrush, combined with the rise in coyote populations, has highlighted the intricate and interconnected nature of Meadow Valley’s ecosystem. Researchers continue to monitor these changes, noting that community interactions among species are constantly evolving in response to new challenges and environmental pressures.

Questions

1. Which type of interaction is represented by the relationship between coyotes and rabbits?

   • (1) Competition

   • (2) Predation

   • (3) Mutualism

   • (4) Parasitism

2. What is one possible impact on the hawk population if the number of rabbits continues to decrease?

   • (1) Hawks will begin to feed on thornbrush plants.

   • (2) The hawk population may decrease due to reduced food availability.

   • (3) Hawks will shift to being herbivores to survive.

   • (4) The hawk population will remain unaffected by rabbit numbers.

3. Identify the type of interaction between the thornbrush and native grasses and wildflowers.

   • (1) Commensalism

   • (2) Competition

   • (3) Mutualism

   • (4) Parasitism

4. Explain how the spread of Thornbrush has impacted the food web in Meadow Valley.
   
   

5. If beetle populations feeding on Thornbrush increase significantly, which of the following is the most likely consequence?

   • (1) An increase in the population of sparrows and wrens due to more available food

   • (2) A decrease in the coyote population as they begin to eat beetles

   • (3) The disappearance of owls from Meadow Valley

   • (4) The decline of native wildflowers due to beetles feeding on them

6. Describe one way in which a decline in pollinators could affect the plant community in Meadow Valley.