Lesson Title: How do larger populations affect resources?
by:  Pamela Wilczynski
Grade Level:  Elementary

Goal:  To give the children an example of how larger populations of yeast use resources so they can relate findings to other populations of animals and plants. 

Learning Objectives: Students will:
predict the results of two different yeast populations in sugar water.
observe what happened to the two cups of water, sugar, and yeast.
compare and contrast the similarities and differences between the two yeast populations by both oral and written methods.
analyze how increasing populations affect an environment.
discover the characteristics that make up a community. 

NJ Science Standards:  5.6:  All students will gain an understanding of the structure, characteristics, and basic needs of organisms.                                                                                                 

Materials/Resources:
I had to buy some packets of yeast for the experiment.  I also had to measure out the appropriate amounts of sugar and yeast into a Ziplock bag so that the students did not have to measure it out from a big container.  I also had to get all the materials ready (water in cups, etc.) before the lesson to save time during the lesson. The following website will provide the necessary background information for teacher and students about what yeast is: http://www.encyclopedia.com/articles/14076.html 

Yeast (3 spoonfuls needed per group)
Warm water
Clear plastic cups (2 per group)
Sugar (2 spoonfuls per group)
Plastic spoon (2 per group)
Science notebooks or journals (1 per child)
Science textbooks (1 per child)
Chalkboard
Chalk
Photographs of bees and other animals in groups for discussion. 

Procedure:

Introduction:  To access prior knowledge, the teacher shows students photographs of bees living together inside a hive. The teacher will ask the students: What can cause the size of the group of bees to change? (possible answer: changes to the environment with examples). Record responses on the chalkboard. The teacher will then tell the students that they will be learning about another population of organisms and how the environment affects that population.   

Exploration:  The teacher will explain to the students that yeast is a population of tiny cells that use sugar as food.  We will observe what happens between yeast and sugar.  The first step is to split the class into 3 groups of 6. The teacher will tell the students not to eat or drink any of the materials in this experiment.  The teacher will have one student from each group come up to the front to get the materials needed.  When all three groups have the materials, the teacher will give all the rest of the students’ jobs (like mixer, pourer, etc.).  Each group will be given 2 cups filled halfway with warm water.  The students as a class will discuss the differences between sugar and yeast and will predict what they think will happen when 1 spoonful of yeast is put into one cup of water and sugar and when 2 spoonfuls of yeast are put into the other cup of water and sugar.  Then the teacher will give the directions to the students and have them follow along as he/she is doing that.  The first step is to place 1 spoonful (which is one Ziplock bag) into each cup of water and stir with the plastic spoons until the sugar is dissolved.  Then the students will add 1 spoonful of yeast (1 Ziplock bag) to one cup and 2 spoonfuls of yeast (2 Ziplock bags) to the other glass.  The teacher will tell the students that as yeast cells use sugar bubbles will form.  The students are then instructed to write what they observe in their science journals. The teacher will let the students observe for a few minutes and will walk around the room visiting each group at this time.  After their observations are written, the students will talk about their observations and what they think is happening and why. The teacher will also ask: What difference did you observe between the 2 cups of yeast? (The cup with two spoonfuls of yeast produced more bubbles).  Why? (It was bigger or a larger population, therefore more yeast needed more sugar as food which caused it to produce more bubbles). The teacher will relate this to the lesson by asking students to compare the two cups of sugar and yeast to populations.  Populations with more people in them need more resources (food, water, shelter, etc.) just like the 2 spoonfuls of yeast needed more sugar for food.  Discuss how an increase in population can affect an environment.  What are some things that might affect the size of a population (availability of space, food, and water); what might happen to a population of squirrels if a disease wiped out the oak trees in the squirrels’ habitat (there will be fewer acorns for squirrels to eat, fewer places for squirrels to live, and the squirrel population might decrease).  The teacher will explain that humans more densely populate some regions of Earth than others do.  Eastern and Southern Asia, Western Europe, and Eastern North America are among the most densely populated regions of the world.  The teacher will ask students to suggest reasons why these areas have such large human populations (excellent farmland, access to water, temperate climate, cultural and religious beliefs, etc.).  Then the class will observe their yeast populations again.  As a class they will talk about what is happening now and record observations in their notebooks or journals.

Then the teacher will ask the students to look back at what they wrote about the bees in the beginning.  The teacher will ask the students if they want to change their answers and if so, why.  Once again the yeast populations will be observed, talked about, and recorded because as time goes on, it begins to bubble more and more and shows distinct differences between the two cups. 

Application:

The students can apply what they have learned today to his/her experience by thinking about humans and animals (and even the yeast experiment) and describing how all of these things work in a population.  They will also be able to see how the environment affects population by thinking of times when the environment has harmed or helped the population.  This lesson can be made relevant in their lives because the students need to learn about populations and how they function because they are a part of a population themselves.

Student Product: 
Lab report on yeast with implications for other populations of organisms. 

Challenge question: What causes the bubbles in the yeast?

Assessment:
Write an essay on what overpopulation or under-population of any species can affect other populations with specific examples (i.e. deer, bears, wolves, feral cats, snakes, people).

Reflection:
There were many strengths to the lesson. It was something fast to do but allowed the students to observe what happened, to record their findings, and to communicate what they found to the class. I prepared the materials by measuring them into little Ziplock bags before the lesson and therefore during the lesson, the students just had to poor certain bags into the cups at certain times. That made it easier for them and for me because time was not wasted specifically counting spoons of materials into cups.  I also split the class into three groups of 6 (one of 7).  This helped the lesson because then there were only 3 experiments going on at a time.  If I had split the class into smaller groups then there would have been more confusion in the classroom.  Also, I made sure that every child in the group had a job.  Someone got the materials, someone stirred, someone poured the sugar, etc.  Therefore everyone had a job and a purpose for the experiment.