The growth and population dynamics lab is purposely multifaceted. It can be used to simply address questions of cell growth, including lag, log, and stationary phases in microbial cultures, but can easily be expanded to encompass questions of population density and sustainability relative to environmental resources. The lab can be used to look issues including including population growth in response to food abundance and shortage and the effects of environmental change (temperature, salinity, water quality, introduction of competitors, etc) on population growth and maintenance. The lab exploits Tetrahymena’s natural lag, log, stationary, crash growth cycle, allowing students to create conditions that examine specific effects on each phase of the cycle, e.g., by input of additional nutrients, removal of nutrients, environmental changes, and changes in population density. Students are encouraged to design their own experiments asking fundamental questions about growth, population, and sustainability.

Module Protocols

Middle School, High School

Relevant Concepts

Population dynamics; Science as a Process; Growth and Survival of Organisms

Next Generation Science Standards Relationships

High School:

HS-LS1-3 Plan and conduct an investigation to provide evidence that feedback mechanisms maintain homeostasis. 

HS-LS2-1 Use mathematical and/or computational representations to support explanations of factors that affect carrying capacity of ecosystems at different scales. 

HS-LS2-2 Use mathematical representations to support and revise explanations based on evidence about factors affecting biodiversity and populations in ecosystems of different scales.

HS-LS3-2 Make and defend a claim based on evidence that inheritable genetic variations may result from: (1) new genetic combinations through meiosis, (2) viable errors occurring during replication, and/or (3) mutations caused by environmental factors. 

Middle School:

MS-LS1-1 Conduct an investigation to provide evidence that living things are made of cells, either one cell or many different number and types of cells.

MS-LS1-2 Develop and use a model to describe the function of a cell as a whole and ways parts of cells contribute to the function. 

MS-LS1-5 Construct a scientific explanation based on evidence for how environmental and genetic factors influence the growth of organisms. 

MS-LS2-1 Analyze and interpret data to provide evidence for the effects of resource availability on organisms and populations of organisms in an ecosystem. 

MS-LS4-4 Construct an explanation based on evidence that describes how genetic variations of traits in a population increase some individuals’ probability of surviving and reproducing in a specific environment. 



●Jaworska JS, Hallam TG, Schultz TW. 1996. A community model of ciliate Tetrahymena and bacteria E. coli: Part I. individual-based models of tetrahymena and E. coli populations. Bull.Math.Biol. 58 (2):247-264.

●Kristiansen TB, Hagemeister JJ, Grave M, Hellung-Larsen P. 1996. Surface mediated death of unconditioned Tetrahymena cells: effect of physical parameters, growth factors, hormones, and surfactants. J.Cell.Physiol. 169 (1):139-148.

●Nelsen EM. 1978. Transformation in Tetrahymena thermophila. Development of an inducible phenotype. Dev.Biol. 66 (1):17-31.

See our glossary for the terms used in the modules.