Lesson 2 – Response of Halo in Different Environmental Conditions

Course:  Biology, Genetics, Biotechnology, Environmental Science

Unit:  Genetics and Heredity


See Standards Addressed for all NGSS and WA State (Science, Math and Literacy).  In addition to the aligned objectives linked above, for this lesson, here is a breakdown of:

What Students Learn:

  • Observations lead to hypotheses and experimental design.
  • Halobacterium (Halo) respond to the amount of light in their environment.
  • Halo change color from pink to purple in the presence of light and from pink to tan/white in the absence of light.
  • Halo grow better in the presence of light.
  • Using a centrifuge separates a culture into a supernatant and pellet, which allows the phenotype of cells to be more easily viewed.
  • Qualitative measurement is a way of describing data with words, whereas quantitative measurement is a way of describing data with numbers.
  • The reliability of data increases with an increase in the size of the data pool/set.
  • To draw reliable conclusions, multiple trials/replicates should be performed.

What Students Do:

  • Students take observation and develop hypothesis and an experiment design.
  • Students use scientific thinking to consider how the environment impacts gene expression and cellular networks.
  • Students conduct a controlled investigation and analyze lab results to determine how the amount of light affects Halobacterium.
  • Students compare, contrast and critique divergent results from their investigations and discuss/identify possible errors/sources of variation.








Pacing Guide

Instructional Activities: (Three 50-min periods, with AT LEAST 72 hours after the 3rd period for incubation)

Before beginning lesson: Read entire lesson. The following documents also may help with prepping for this lab:


Students reviewed literature about a model organism (Halo) during Lesson 1 which gave the students an opportunity to investigate the environmental conditions Halo typically grow in. The Lesson 2 laboratory experience will give students an opportunity to actually see the effect of certain environmental variables on the Halobacterium organism. Depending on the time constraints and goals for this lesson – there are 3 possible pathways. Here are the possibilities:
1.    Students work with a defined manipulated variable – presence of light – AND a defined, predetermined lab protocol. NOTE – This will remove one 50 minute period from the time required for this lesson, however it will be harder to present as inquiry: observations lead to hypotheses and experimental design.
2.    Students work with a defined manipulated variable – presence of light – they will design a laboratory experiment using this manipulated variable which then can be carried out in the laboratory. Teacher will need to guide students with the availability of their laboratory supplies (use of stir stations, agitating incubator, bubbler system).
3.    Students work with different manipulated variables that are determined during their Lesson 1 research. The possible variables that can be easily manipulated using the kit (provided you have enough lab equipment) are: light, oxygen, salinity, color of light, pH, temperature, amino acid concentration, presence of metals or oil.
·         There is a document which will help outline expected results and other helpful hints for this version of the lab (Teacher Lab Hints-variables).