Open ended
Based on your focus for your class goals and objectives this explanation could be something as simple as how effective is soap to the differences in species richness and biodiversity in leaf litter and soil. I didn't want to funnel anyone into a specific area so hear are some ideas, but remember you have goals for your classroom use these activities to enhance your goals.
Objectives
The learner will discuss biodiversity and how it can be measured.
The learner will compare the species richness of a .25m quadrant to a gram of soil.
The learner will determine if 99.9% effective is good enough for antibacterial soap.
Materials
Data from the activities.
Procedure
1.  Using the species richness data from the leaf litter and the bacterial plates have the students determine which one is more diverse?
2.  This is a good time to bring up sample methods and the trophic level of the sample.
3.  Take the class averages for the number of cells in a gram of soil and determine if your antibacterial soap is really helping. Use this to incorporate ideas like antibiotic resistance.
4.  Have the students evaluate the idea of species richness. Is this a good way to measure biodiversity. Then try using another index like the shannon index to evaluate the biodiversity. How do the two relate?
References
Biodiversity analysis at Biofilms and Biodiversity website, www.mdsg.umd.edu/Education/biofilms.htm 
State Standards
1.1.1- The student will recognize that real problems have more than one solution and decisions to accept one solution over another are made on the basis of many issues.
1.1.2- The student will modify or affirm scientific ideas according to accumulated evidence.
1.1.3- The student will critique arguments that are based on faulty, misleading data or on the incomplete use of numbers.
1.1.4- The student will recognize data that are biased.
1.1.5- The student will explain factors that produce biased data (incomplete data, using data inappropriately, conflicts of interest, etc.).
1.2.1- The student will identify meaningful, answerable scientific questions.
1.2.6- The student will identify appropriate methods for conducting an investigation (independent and dependent variables, proper controls, repeat trials, appropriate sample size, etc.).
1.2.7- The student will use relationships discovered in the lab to explain phenomena observed outside the laboratory.
1.4.1- The student will organize data appropriately using techniques such as tables, graphs, and webs (for graphs: axes labeled with appropriate quantities, appropriate units on axes, axes labeled with appropriate intervals, independent and dependent variables on correct axes, appropriate title).
1.4.2- The student will analyze data to make predictions, decisions, or draw conclusions.
1.4.3- The student will use experimental data from various investigators to validate results.
1.4.6- The student will describe trends revealed by data.
1.5.1- The student will demonstrate the ability to summarize data (measurements/observations).
1.5.2- The student will explain scientific concepts and processes through drawing, writing, and/or oral communication.
1.5.4- The student will use tables, graphs, and displays to support arguments and claims in both written and oral communication.
1.5.8- The student will describe similarities and differences when explaining concepts and/or principles.
1.7.2- The student will identify and evaluate the impact of scientific ideas and/or advancements in technology on society.
Lesson Resources