Subject
Home
/
Biology
/
this is the method used. 1. grow gonorrhoea bacteria in a petri dish. 2. prepare four different antibiotic solutions, a b, c and d of

Question

This is the method used. 1. Grow gonorrhoea bacteria in a Petri dish. 2. Prepare four different antibiotic solutions, A B, C and D of the same conc 3. Cut four filter paper discs to the same size. Soak each paper disc in a different antibiotic solution. 5. Put the four paper discs into the Petri dish. 6. Repeat steps 3 to 5 using a Petri dish with chlamydia bacteria growing in 7. Keep both Petri dishes at 25^circ C for 3 days. (c) Give two control variables used in this investigation. __ 1

Answer

4.2 (182 Votes)
Verificación de expertos
Mabel Master · Tutor for 5 years

Answer

1. The antibiotic concentration: This was kept constant across all four antibiotic solutions, meaning the variation in antibiotic effectiveness on bacteria growth observed in the experiment was due to differences in the specific antibiotics used, and not because of varying concentrations. 2. The size of the filter paper: All filter paper disc sizes were maintained equal in the experiment. This ensured that the quantity of the antibiotic solution applied on each disc was equal. 3. The environmental conditions: All Petri dishes were kept at the same temperature for the same length of time, ensuring that changes in environmental conditions didn't leave an impact on readings between the different trials of the experiment. In conclusion, antibotic strength, filter paper size and environmental conditions were the control variables in the experiment.

Explanation

## Step 1: Identify the variables in the scenario.The scenario describes an experiment into the effects of different antibiotic solutions on two types of bacteria: gonorrhoea and chlamydia.## Step 2: Discern the control variables.Control variables are quantities, parameters, or conditions that a scientist keeps constant during an experiment in order to reduce influences from external factors which could affect the outcomes. In the provided experiment, scientists kept the same concentration for all antibiotic solutions, used the same sized filter paper discs, and maintained both Petri dishes at the same temperature of for the same period of time.