b) Identify a dependent variable in the experiments. Identify the reasoning of the scientists when they tested the number of colonies produced by strains C3-PBB and C6-PBB . The scientists also analyzed the number of colonies produced from each of the environmental and clinical isolate strains when the strains were plated on a growth medium lacking the toxic chemical. Justify this analysis.

A dependent variable is the number of colonies produced. The experiment gives a useful insight into the toxicity of the chemicals.

A scientific experiment must always have a dependent and an independent variable. A dependent variable is the variable whose outcome is being determined by manipulating the independent variable which in this case is the presence or absence of the chemicals.

Toxicity of chemical substances is a very important information to scientists as such this experiment is very important because it highlights the toxicity of the chemicals to living things.

Learn more: link

Explanation:

Dependent variable is the outcome that is measured. This is the number of colonies produces by the clinical Isolate strain. Without the growth media the strain cannot thrive or reproduce hence their dependent on the media for survival.

While independent variable is the treatment that is varied in an experiment. It usually not dependent on any variable and can stand on it own.

The growth media that is lacking in chemical is the independent variable because it stands on it own and it can be carried depending on the experimental design it could be a chemical based growth media or no chemical like the one used in this experiment.

this would be a math

sheep is a herbivore animal whereas grasshopper belongs to the class chordates but both of them feed on greens.  

if grasshopper and sheep feeding on a pasture land, i do not think both of them will have any impact on each other. however, the number of the species can make difference. since sheep feed on greens, there is a possibility there left no pasture land for the grasshoppers or they may get extinct.