Bacteria Growth (Amanda Hrezo)

Research Question and Hypothesis

1. What type of population growth does bacteria in petri dishes exhibit?

   1. More bacteria will grow in the larger petri dish.

2. Does antibacterial soap work?

   1. Less bacteria will grow when antibacterial soap is used

Standards

1. HS-LS2 Ecosystems: Interactions, Energy, and Dynamics

2. HS-LS4-4. Construct an explanation based on evidence for how natural selection leads to adaptation of populations.

Experimental Design

Each group of students will obtain a petri dish of either small, medium or large. Over the course of two weeks the students will collect data about how much bacteria there is on their plate. At the end the students will compare the amount of bacterial growth over time in comparison to the other size petri dishes. The hope is that the students will see exponential growth in the larger dishes and logistic growth in the smaller dishes. From there the students can hypothesize about why there were two different growth patterns.

Independent variable

Petri Dish Size (Small, Medium, Large)

Dependent variables

Bacteria Population Size

- Percent covered of petri dish covered

or

- Count Colonies and Quantity them based on size (x-small (0.1-)= small=1, Medium=2, Large= 3, x-large=4, ect.)

Series

Study the bacteria growth as a function of resources over time

Study the impact of antibacterial soaps (natural selection antibiotic resistance)

Constants and Controls

• Type of agar

• location

• amount of light

• temperature

Materials

Petri Dishes- From any science supply store such as flinn

Agar- From any science supply store such as flinn

Incubator- Not necessary but can help bacteria grow faster, from any science supply store such as flinn

Sharpie- Walmart

Tape- Walmart

Antibacterial Soap

Procedures

1. Obtain petri dish with agar (microbe food) from teacher

2. Record group members names and period on bottom of plate using a sharpie or china marker

3. Open plate lid for the entire period 40 minutes.

4. Record at least 3 observations about your location and the appearance of the plate

5. Take a picture of the plate using a smart phone from your group. Make sure to save it for later when you create your group lab report mini-poster.

6. Place lid back on petri dish and secure with tape

7. Return petri dish to teacher

8. Record data each day

   1. DO NOT OPEN THE LID!!!

   2. Record the percentage of the petri dish that is covered by growth

Sample data and graphs

Data Spreadsheet

Analysis & Conclusions

The antibacterial side had more growth than the control side. The germ-x side should of had less bacterial coverage but there is still typically bacteria growth.

Photos & Movies

Day 5

References

- Antibacterial lab

- Limiting Resources Population Lab