It's Alive! (Hien Phan)

Title: It's Alive!

Principle(s) Investigated: Fermentation, Resource availability

Standards:

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

MS-LS1-7. Develop a model to describe how food is rearranged through chemical reactions forming new molecules that support growth and/or release energy as this matter moves through an organism

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

Materials:

  • 2 cups of warm water
  • 2 tsp of yeast
  • 3 tbsp of white granulated sugar
  • 2 mason jars
  • food thermometer
  • sandwich ziplock bag
  • hair tie or rubber band
  • stirring device

Procedure:

  1. Heat up 2 cups of water. Use the food thermometer to ensure the water temperature is between 105.0 - 110.0 degrees F.
  2. Pour 1 cup of warm water into each mason jar.
  3. In the first mason jar, pour in 1 tbsp of sugar and mix until sugar dissolves. In the second mason jar, pour in 2 tbsp of sugar and mix until sugar dissolves.
  4. Add 1 tsp of yeast to each mason, making sure to spread the yeast out.
  5. Cover each mason jar with a ziplock bag and use the hair tie/rubber band to keep the ziplock bag in place
  6. Wait 5-7 minutes and let the yeast grow. Observe and measure the growth of the yeast.

Student prior knowledge:

  • Students should have prior knowledge of single-cell organisms
  • Students should have prior knowledge of ecosystems
  • Students should have prior knowledge of chemical reactions

Explanation:

We know that there are multiple environmental factors that affect organisms' growth and population size in an ecosystem. Such factors can be temperature, availability of food, light, abiotic factors, biotic factors, water, and so on. Yeast is a eukaryotic, single-cell organism that is part of the fungi family. Yeast's primary "food" source comes from sugar. To create energy for itself, yeast breaks down sugar through the process of fermentation to create alcohol and carbon dioxide with the release of energy.

Glucose → ethanol + carbon dioxide + energy

or

C

6

H

12

O

6

→

2

C

2

H

5

O

H

+

2

C

O

2 + energy

Compared to respiration, fermentation doesn't require oxygen to create ATP, however, less ATP is created. There are two types of fermentation: ethanol and lactic acid fermentation. The fermentation process that occurs in yeast is ethanol fermentation, hence, the production of alcohol. The more sugar readily available to yeast, the more energy it can produce, and the faster the population will grow.

Each mason jar had the same amount of water and yeast added and were both at the same temperature. The only difference was the amount of sugar added. The jar with 2 tbsp of sugar added showed a larger increase (about 1/3 more) in yeast growth in comparison to the mason jar with 1 tbsp of sugar added.

Questions & Answers:

1. What is another environmental factor that can be manipulated to examine the environmental effect on the blooming of yeast?

  • Liquid temperature, such as using colder or hotter water. We know that the ideal temperature for yeast to bloom is between 105-110 degrees F, therefore, controlling the water temperature can change the rate of blooming or whether or not yeast will survive at higher temperatures than 110 degrees F.

2. Can yeast be acquired naturally?

  • Yes, these are considered as "wild" yeast in comparison to the "domesticated" species of yeast we find in packets at the grocery stores. There are wild yeast spores floating around in the air in our environment. To capture them, one would create a mixture of starch (flour) and water, cover with a cloth (like a cheesecloth), and let it sit out. Over a period of a few days, some of the yeast in the air will make its way to the mixture and start dividing and growing.

3. How does human activity affect resource availability in ecosystems?

  • Human activities and growth can displace animals and resources from the ecosystem they once reside in. Humans can destroy forests for logging, pollute freshwater with factory runoffs, introducing non-native species to ecosystems, and much more.

Applications to Everyday Life:

1. Food and alcoholic beverages - Ethanol fermentation is utilized in breweries to create alcoholic beverages such as wine and beer. The specific yeast species used for beer brewing is Saccharomyces cerevisiae in warmer temperatures and Saccharomyces Pastorianus in cooler temperatures. Yeast can also be found in bread. Water is added to flour to break down the starch molecules into sugar molecules for the yeast to utilize. The holes you see in bread are the carbon dioxide gasses dropped in the dough when it is proofing and baking.

2. Algae growth in a swimming pool - Have you ever noticed how some swimming pools feel slimy or how there's a layer of green film at the bottom of the pool? That's algae! Algae is a eukaryotic organism that uses photosynthesis to create energy. These organisms live and thrive in aquatic environments so pools are right on target. Algae spores are carried can be carried by wind and rain. With the right environmental conditions and resources (such as warm, sunny days, higher levels of debris, unfiltered water, etc) algae can proliferate and grow in your swimming pool.

3. Logging deforestation - Logging deforestation in the Amazon rainforest leads to habitat loss, soil erosion, flooding, increased greenhouse gas, and so much more. Trees and vegetation in the rainforest act as sources of food, shelter, and breeding habitats for many animals. With the destruction of these resources, the animal population can decrease due to the lack of proper resources and protection from predators.

Photographs: