Final answer:
A change in the population size of one species affects another species differently depending on their relationship. In a predator-prey scenario, more predators could decrease prey numbers. When species compete for resources without direct interaction, one species' increase might not affect the other if resources are abundant.
Step-by-step explanation:
When considering how a change in the population size of one organism affects another, it's important to look at the relationships between species in an ecosystem. If, for example, we have two species where Species A is a predator and Species B is its prey, an increase in the population size of Species A would likely lead to a decrease in the population size of Species B. This is because more predators would increase the predation pressure on the prey.
Conversely, if Species A's population size decreases, we might see an increase in the population size of Species B, as the reduced predation pressure allows their numbers to recover. However, if the creatures have overlapping needs for food and nesting space, but do not directly interact (like predator and prey), then the increase in population of Species A could have a different impact. If Species A's population grows due to the abundance of resources, it won't necessarily affect Species B's population size if the resources are not limiting.
Therefore, the effect of a change in population size of one species on another is highly context-dependent and varies with the nature of their interactions within the ecosystem.