Here we have 4 situations that modify the ecosystem and 2 graphs that represent the decrease (left) and decrease (right) in population size.
So, we need to look at the events and determine if they are positive or negative for the population:
• Habitat loss caused by a volcanic eruption, ,would mean fewer resources and will cause a ,decrease, in the population size.
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• Decreasing water pollution in an aquatic ecosystem, would be beneficial for the living beings there, so the population size would ,increase.
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• Desertification due to excess industrialization, would be another way of losing habitat, so it would cause a, decrease, in the population size.
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• Building a national park to conserve plants and animals, would allow the population ,grows.
This means that the graph on the left (decrease) corresponds to habitat loss caused by a volcanic eruption and desertification due to excess industrialization; while the graph on the right (increase) corresponds to decreasing water pollution in an aquatic ecosystem and building a national park to conserve plants and animals.