A research scientist wants to determine if the type of ground cover (mulch) affects the reproductive yield of cherry tomato plants (Solanum lycopersicum).
She grows cherry tomato plants in identical pots containing a standard peat-free compost mix:
After five months, the scientist harvests all tomatoes from each pot, dehydrates them in an oven at 80 °C until a constant mass is achieved to determine their dry mass, and calculates the mean dry mass of cherry tomatoes per pot.
The results are shown in the bar chart below:
State the independent variable in this scientific investigation.
Describe the steps the scientist takes to make sure her results are reliable.
To make a valid comparison, the scientist must control other environmental variables. She places all the pots in the same temperature-controlled growth chamber to keep the ambient temperature constant. Name three other abiotic factors she must control.
Suggest two biological reasons why the tomato plants yield a higher dry mass of fruit when the soil is covered with a reflective silver plastic film compared to being left uncovered (bare soil).
