Here's a hypothesis for the duckweed experiment: “if duckweed is grown at ph 5, then it will grow at the same rate as when grown at ph 7, or normal ph, because it can tolerate mildly acidic environments.” which elements should be controlled variables for this experiment? check all that apply. environmental ph timing of experiment duckweed population environmental light amount of nutrients environmental temperature

The controlled variables in an experiment are those variables which are kept same in the overall reaction in every trial. It is kept as a benchmark or standard for all the variables that testable samples are exposed with.  

Timing of experiment: The timing of the experiment can be used as a controlled variable as a particular time constraint can be used to perform an experiment.

Duckweed population: The duckweed population should be kept as a constant to observe the impact of variables on the duckweed populations.

Environmental light: A particular environment light can be used as a standard under the influence of which the duckweed population shows growth.

Environmental temperature: A controlled standard temperature can be chosen for every trial to observe the growth of the duckweed.

high growth (apex)