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Which change would create a new ecosystem?

• an introduced species
• a lake freezing over
• a dam flooding a valley
• a yearly migration

3 answers

Among the options provided, the change that would most likely create a new ecosystem is "a dam flooding a valley."

When a dam is built and it floods a valley, it can result in a complete transformation of the environment. This would create a new aquatic ecosystem where there was previously terrestrial habitat. The flooded area would support different species of plants and animals that thrive in wetland or aquatic environments, fundamentally altering the existing ecological dynamics.

While an introduced species can affect an existing ecosystem, and a lake freezing over can alter seasonal conditions, they do not necessarily create an entirely new ecosystem in the same way that flooding a valley would. A yearly migration is also a natural phenomenon that affects existing ecosystems rather than creating a new one.

Analyze the components of the ecosystem. What is the most likely outcome if the mountain lion population vanishes?
• The trout population will decrease.
• The stream will become polluted.
• The deer population will decrease.
• The deer population will increase.

If the mountain lion population vanishes, the most likely outcome is that the deer population will increase.

Mountain lions are apex predators and play a crucial role in controlling the population of deer and other prey species. When apex predators like mountain lions are removed from an ecosystem, there is typically an increase in the population of their prey species due to the reduced predation pressure. In this case, with fewer mountain lions to hunt them, deer populations are likely to grow.

Though the increased deer population could lead to other ecological consequences (such as potential overgrazing and negative impacts on vegetation), the direct effect of the absence of mountain lions would primarily result in an increase in deer numbers.

The other options provided:

  • The trout population will decrease: This is not directly related to the mountain lion population.
  • The stream will become polluted: While increased deer populations could lead to more nutrient runoff, this is not a direct or immediate consequence of the absence of mountain lions.
  • The deer population will decrease: This is the opposite of what is expected.

Thus, the correct answer is that the deer population will increase.