Adaptations of Microscopic Freshwater Organisms

TEAM MEMBERS: Jeremy S. Krimmel

AUTHOR: Jeremy S. Krimmel

DATE LESSON TO BE TAUGHT: ???

GRADE LEVEL: 9-12

CONCEPT:

• Organisms evolve over generations to become better adapted to their environments.
• Organisms exist on scales much more minute we can see with the naked eye.

OBJECTIVES:

Students will be able to…

• …make observations of organisms that they have little to no previous knowledge of.
• …create a theory of how evolution has shaped an organism to better fit its environment.
• …present to the class a valid argument for how an organism has evolved.

MATERIALS LIST and ADVANCED PREPARATIONS:

• Microscope (1 per 4 students)
• 1 liter sample of river or creek water
• Bottle of saltwater

SAFETY:

• Students should be reminded early and often to not drink the water

ENGAGEMENT

What the Teacher Will Do	Eliciting Questions	Student Responses
Show the class pictures of a hooded seal, duck-billed platypus, ocean sunfish, tubeworm, octopus, giant squid, or any other remarkably odd creatures	1) What makes these creatures different than animals we normally see? 2) Why and how did they become so different?	1) Responses will vary 2) [To become more fit; natural selection]; to match their environment; to be more comfortable
Break the class into groups of 4, tell them to come up with characteristics that will allow a made up organism to survive given certain conditions	1) What characteristics will allow the organism to survive? 2) How could these characteristics arisen from a particular ancestor?	Responses will vary for both questions; teacher must use knowledge of process of evolution to guide discussion

EXPLORATION

What the Teacher Will Do	Eliciting Questions	Student Responses
Give each group a sample of water and a microscope and ask the students to jot down the various organisms they see in the water in their notebook	1) Do these organisms have any common characteristics? 2) What must be in common for them to all survive? 3) What must be different for them all to survive? 4) What characteristics have these organisms developed in order to be adapted to their aqueous environment?	1) Responses will vary but will mostly deal with appearance 2) [Ability to survive in water]; must eat each other 3) [Must fulfill different roles of an ecosystem on a minute scale]; must look different; must eat different things 4) [Chemical processes that allow for submersion in water; means of propulsion; ability to extract nutrients from water]; must be see-through
Give each student a certain amount of saltwater solution to add to their sample of water	1) How can you measure the approximate number of these organisms in the sample of water?	1) [Relative concentrations in view]; counting (too time-consuming)
Tell the students to once again jot down what they see in their notebooks	1) What has happened to the number of organisms in the water? 2) Do the organisms look any different?	1) Responses will vary depending upon how much saltwater was put into the sample and how much time was given 2) [No, they look the same]
Have students continue adding salt until marked changes in the number of organisms is detected	1) What does this reveal about the ability of the organisms to tolerate salinity? 2) If their environments suddenly became saline, would these organisms survive in any way?	1) [They can’t tolerate it very well] 2) [Yes, those who can tolerate it would reproduce and make others that could tolerate it]; no, they would go extinct

EXPLANATION

What the Teacher Will Do	Eliciting Questions	Student Responses
Tell each group to send a representative to the front of the class to discuss one of the organisms found in their sample of water and all the information they could gather about it	1) What does this organism look like? 2) What physical characteristics has this organism developed in order to adapt to its aqueous environment?	1) Students will draw a picture of it on the board 2) Responses will vary
Present a brief lecture with information about each of the organisms found in the water	1) How do the observations you made today align with the information from the lecture?	1) Responses will vary depending on the hypotheses they made on the adaptations of the various organisms

ELABORATION

What the Teacher Will Do	Eliciting Questions	Student Responses
Allow students to test for the organisms’ reaction to other environment changes other than salinity including sunlight and temperature; samples can even be left overnight if desired	1) What other environmental factors affect the life of the organisms in the water? 2) How can you test their effects?	1) Sunlight, temperature, exposure to oxygen, whether there is any fresh oxygen to the system over time 2) Students will develop basic ideas for experiments that can be run if there is sufficient time

EVALUATION

• Students’ notebooks for observations on the organisms in the water
• Students’ presentations for the understanding of how adaptations might appear
• A written assessment can be passed out following the lecture stressing the correlation between the information presented in lecture and the observations made during class