Multiple choice:
For a natural ecosystem to be self-sustaining,
many compounds must be:
1. converted into new forms of energy.
2. cycled between organisms and the environment.
3. permanently removed from the environment.
4. changed into fossil fuels such as oil and
coal
2: cycled between organisms and the environment
The compounds must be taken in by consumption, and then recycled back through decomposition.
cycled between organisms and the environment
To find the correct answer, we need to understand what it means for a natural ecosystem to be self-sustaining. This means that the ecosystem is able to maintain its balance and continue functioning without relying on external inputs.
Now let's analyze the options:
1. Converted into new forms of energy: While energy conversion is important for the functioning of an ecosystem, it alone does not ensure self-sustainability. Energy flow is necessary for organisms to carry out their metabolic activities, but the ecosystem also needs other compounds for its long-term stability.
2. Cycled between organisms and the environment: This option sounds promising as cycling compounds between organisms and the environment is a crucial aspect of self-sustainability. Nutrients, such as carbon, nitrogen, and phosphorus, are continuously cycled through the ecosystem, being taken up by organisms, recycled, and returned to the environment in various forms.
3. Permanently removed from the environment: If compounds were permanently removed from the environment, the ecosystem would eventually be depleted of those essential elements, which would lead to its collapse. Therefore, this option is not consistent with self-sustainability.
4. Changed into fossil fuels such as oil and coal: The conversion of compounds into fossil fuels is a geological process that takes millions of years. While it is a natural process, it is not directly related to the self-sustainability of an ecosystem.
From our analysis, it is clear that option 2, "cycled between organisms and the environment," best describes the process that allows a natural ecosystem to be self-sustaining.