Living in an Alkaline Environment
Activity at a Glance
Purpose Overview Key Concepts Key Skills Time Materials 5-8 Standards 9-12 Standards
Part 1: To show many ways in which Mono Lake water and distilled water are different
Part 2: To demonstrate that the survival of common soil bacteria declines as pH increases
Part 3: To examine the behaviors, adaptations, energy transfer, and diversity of organisms in an alkaliphilic habitatBack to Top
Part 1: Students compare distilled water with simulated Mono Lake water by conducting eight tests at four activity stations. They also observe two teacher demonstrations. They record the results of this testing on a student handout. They see that Mono Lake's high pH and high salt and mineral content make its water considerably different than distilled water. They discuss how Mono Lake's extreme chemistry might stress organisms adapted for a typical pond, lake, or river and answer four questions on the student handout.
Part 2: Students use soil bacteria from the local environment to inoculate four agar plates with pH ranging from 7 to 10. After 24-48 hours, they count the number of colonies on the plates and create a graph comparing the number of colonies and the pH. They see that survival declines as pH increases. They then visit the Marine Biological Laboratory's online microscope to see that, in fact, there are organisms adapted to living in Mono Lake's extreme environment. They brainstorm a list of adaptations that organisms living in such an environment might have and answer four questions on the student handout.
Part 3: Students do a WebQuest and see that organisms in alkaliphilic habitats have unique and sometimes complex food webs, behaviors, adaptations, and overall diversity.Back to Top
- Mono Lake is an extreme environment, with a pH of 10 and a high salt and mineral content
- High pH denatures proteins and dissolves fats
- Survival of common soil bacteria declines as the pH rises
- The limited number of organisms able to tolerate Mono Lake's extreme environment means less competition for resources and fewer predators for those able to live there
- Organisms expend valuable metabolic resources to survive Mono Lake's extreme conditions
- Life will adapt in order to take advantage of available sources of energy and nutrients
- Alkaliphiles maintain an internal pH of 7.5-8.5, regardless of the environmental pH
- At high pH, alkaliphilic bacteria activate a sodium-ion pump, which begins a process that lowers the internal pH by transporting hydrogen ions into the cell
- Alkaliphilic enzymes have a special composition that protects them from being denatured
- Alkaliphiles' cell membranes have a special composition that protects them in Mono Lake's highly-alkaline conditions
Part 1: Comparing different substances; Measuring pH; Measuring specific gravity
Part 2: Inoculating agar plates; Counting colony abundance on an agar plate; Creating a graph
Part 3: Conducting a WebQuest; Synthesizing information from a WebQuest Back to Top
(One day is considered to be a 50-minute class)
Part 1: Day 1: Visit the activity stations; Day 2: Conduct the demonstrations & discussion
Part 2: Day 1: Inoculate plates; Day 2: Brief observation; Day 3: Final observation & graphing
Part 3: Day 1: Begin WebQuest; Day 2 - 3: Finish WebQuestBack to Top
Part 1: Student sheets, Distilled water; Table salt; Baking soda, Epsom salt; Borax; Detergent containing phosphate (e.g., Spic & Span); Sodium hydroxide (Sodium hydroxide is readily and inexpensively available as lye in hardware and grocery stores); Dropper bottles; pH meters, papers, or strips; Cooking oil; Wax paper; 100 ml, 500 ml and 1000 ml beakers; Specific gravity hydrometer or rods/spheres that indicate density by floating or sinking; 2 dishpans; Dozen eggs; 4 teaspoons; Paper towels or sponge; Heat source (e.g., Bunsen burner, candle, alcohol burner); 2 spoons with insulated handles (or oven mitt); Dropper bottle of vinegar; microscope whose image can be displayed on a computer or projection screen; Microscope slide; Cover slip; Tissue or other absorptive material; Cellular stain (if necessary for clarity)
Part 2: Student sheets; Soil samples; 2 Liter Flask, 40-50 Petri dishes; Hot plate w/ stirrer and stir bar; Aluminum Foil; pH strips, litmus paper, or pH meter; 40 g tryptic soy agar (powder, pre-made, or Easy-Gel), 0.1 M Hydrochloric Acid; 0.1 M Sodium hydroxide
Part 3: Computer lab with internet connectionBack to Top
National Science Education Standards, Grades 5-8
Grades 5-8: Physical Science-Content Standard B, Properties and Changes of Properties in Matter
- A substance has characteristic properties, such as density, a boiling point, and solubility. One can separate a mixture into the original substances using one or more of these properties.
- Substances react chemically in characteristic ways with other substances to form new substances (compounds) that have different characteristic properties.
Grades 5-8: Life Science-Content Standard C, Structure and Function in Living Systems
- All organisms are composed of cells, and most organisms are single celled.
- Cells carry on the functions needed to sustain life, including making the materials it needs.
Grades 5-8: Life Science-Content Standard C, Regulation and Behavior
- All organisms must be able to obtain and use resources, grow, reproduce, and maintain stable internal conditions while living in a constantly changing external environment.
- Regulation of an organism's internal environment involves sensing the internal environment and changing physiological activities to keep conditions within the range required to survive.
Grades 5-8: Life Science-Content Standard C, Diversity and Adaptations of Organisms
- Species acquire many of their unique characteristics through biological adaptation, which includes changes that enhance survival and reproductive success in a particular environment.
Grades 5-8: Earth And Space Science-Content Standard D, Structure of the Earth System
- Water is a solvent, dissolving minerals and gases, which it carries to lakes and oceans.
Grades 5-8: Science In Personal And Social Perspectives-Content Standard F, Natural Hazards
- Internal and external processes of the earth system cause natural hazards, including the toxic build-up of naturally-occurring substances, such as minerals, salts, acids, and bases.
National Science Education Standards, Grades 9-12
Grades 9-12: Physical Science-Content Standard B, Chemical Reactions
- In acid/base reactions, hydrogen ions transfer between reacting ions, molecules, or atoms.
Grades 9-12: Life Science-Content Standard C, The Cell
- A membrane surrounds each cell, separating it from the outside world. Cells carry out such functions as homeostasis, transport of molecules, and synthesis of new molecules.
- Most cell functions involve chemical reactions.
- Cell functions are regulated. This regulation allows cells to respond to their environment.
Grades 9-12: Life Science-Content Standard C, Biological Evolution
- Evolution is the consequence of the interactions of a finite supply of resources required for life and the ensuing selection of those offspring better able to survive and leave offspring.
- More than 3.5 billion years of evolution has filled every available niche with life forms.
Grades 9-12: Life Science-Content Standard C, Matter, Energy, and Organization in Living Systems
- The distribution and abundance of organisms and populations in ecosystems are limited by the availability of matter and energy and the ability of the ecosystem to recycle materials.