
When tackling complex reasoning tasks, you have access to the following actions. Use them as needed to progress through your thought process.

[ASSESS]

[ADVANCE]

[VERIFY]

[SIMPLIFY]

[SYNTHESIZE]

[PIVOT]

[OUTPUT]

You should strictly follow the format below:

[ACTION NAME]

# Your action step 1

# Your action step 2

# Your action step 3

...

Next action: [NEXT ACTION NAME]


system
Research Topic: "Investigating the Relationship Between the Number of Yeast Populations and Time in Culture Medium"  
Experimental Materials and Tools: Yeast strains and sterile culture medium, test tubes, hemocytometer, pipettes, microscope, etc.  
Method of Yeast Microscopic Counting:  
1. Hemocytometer: A glass slide with small squares (2mm×2mm×0.1mm) scale for counting microorganisms under a microscope;  
2. Drop the culture containing yeast on the counting board, calculate the number of yeast in a small square, and then estimate the total number of yeast in the test tube. Observe continuously for 7 days and record the daily quantity.  
Based on the above description, answer the following questions:  
(1) The experimental hypothesis of this topic is: Initially, the yeast population shows "J" type growth, and as time goes on, the yeast shows "S" type growth.  
(2) The reason why this experiment does not set up a control experiment is.  
(3) The purpose of gently shaking the test tube several times before drawing the culture medium for counting is.  
(4) If the number of yeast in a square under the microscope is observed to be $a$, then the total number of yeast in 1mL of culture medium is approximately.  
(5) A student performed the following operations. Among them, the correct operations are (fill in the serial numbers of the operations).  
① Put an appropriate amount of dry yeast into a conical flask containing a certain concentration of glucose solution and culture under suitable conditions  
② After standing for a while, use a pipette to draw the culture medium from the conical flask  
③ Drop a drop of culture medium in the center of the hemocytometer and cover it with a cover slip  
④ Use filter paper to absorb the excess culture medium at the edge of the hemocytometer  
⑤ Place the counting board in the center of the stage, wait for the yeast to settle to the bottom of the counting chamber, and observe and count under the microscope.

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