Anyone know the answer to this bio question?

The independent variable is what the experimenter changes and the dependent variable is the variable that changes in accordance to what is done to the independent variable.

So, the right answer is the second one.

Explanation:

For example, if you were testing plant growth according to how much water was added, the volume of water added would be the independent variable and the rate of plant growth would be the dependent variable since how much water you add will affect how much the plant grows.

answer: once a climax community is reached, there are no nutrients left in the ecosystem to support the growth of plants.

an ecological succession involves subsequent changes in the ecosystem because of change in biotic and abiotic factors. with each subsequent succession there is change in the ecosystem diversity. these changes continues until the ecosystem attains complete stability. the last stable level of succession includes the climax community. because of increase in diversity at each successional level the resources left till an ecosystem reaches the end climax community will not able to sustain the inhabiting species. once a climax community is reached, there are no nutrients left in the ecosystem to support the growth of plants as soil being the same abiotic factor in each successional level has lost it's fertility for growth of plants.