Bacteria Growth (Amanda Hrezo)
Research Question and Hypothesis
What type of population growth does bacteria in petri dishes exhibit?
More bacteria will grow in the larger petri dish.
Does antibacterial soap work?
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
Obtain petri dish with agar (microbe food) from teacher
Record group members names and period on bottom of plate using a sharpie or china marker
Open plate lid for the entire period 40 minutes.
Record at least 3 observations about your location and the appearance of the plate
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.
Place lid back on petri dish and secure with tape
Return petri dish to teacher
Record data each day
DO NOT OPEN THE LID!!!
Record the percentage of the petri dish that is covered by growth
Sample data and graphs
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 1 Day2
Day 3 Day 4
Day 5