Part 1: Stimulus, Response, and Behavior
To introduce the lesson, ask students, “Why do bears catch salmon?” For several minutes, list students’ answers on the board. Accept all reasonable responses.
Write on the board, “Behavior is an organism’s response to a stimulus.” Have several students suggest definitions for “stimulus” and “response.”
Hand out the Stimulus, Response, and Behavior worksheet (S-6-3-3_Stimulus, Response, and Behavior and KEY.docx). Have students record the definitions of behavior, stimulus, and response on Part 1 of the worksheet.
Explain the difference between instinctive and learned behaviors, and relate them to the opening question about dogs chasing cats (an innate behavior). Have students give examples of several other instinctive and learned behaviors of dogs.
Explain, “A basic trait of all organisms is the ability to respond to changes in the environment. Examples are changing color, migrating, and hibernating.”
Conduct the following whole-class activity. Display the Responses to Environmental Changes grid (S-6-3-3_Responses to Environmental Changes and KEY.docx). For each item in the Response column, have students identify the type of environmental factor that provides the stimulus. Check off the stimulus for each item. Discuss any responses that may match more than one stimulus.
Ask students to read the examples of stimuli and responses in Part 2 of the worksheet and write his/her own examples below them.
Have students work in small groups to complete Part 3 of the worksheet by cutting and pasting the missing stimulus or response for each type of organism. Review the answers to Part 3 of the worksheet by calling on students from each group to present answers.
Conclude this part of the lesson by repeating the concepts of instinct and learned behaviors, stimuli, and responses. Give students an example of a stimulus (e.g., shut a book loudly without warning) and ask them to describe the responses they noticed in themselves (e.g., jumping, increased heart rate).
Part 2: Organisms Respond to Changing Environments
Have students read the Snowshoe Hare article (S-6-3-3_Snowshoe Hare Article.docx) and describe how the snowshoe hare responds to changes in seasons. Ask them to describe how other animals respond to seasonal changes (e.g., wolves grow thicker fur; chipmunks become dormant during the winter).
Tell students, “The octopus belongs to a group of marine animals called Cephalopods. They have been around since the late Cambrian period, several million years before the first primitive fish began swimming in the ocean!” Ask students to recall why the Cambrian period is important to Earth’s history. (It is when many multicellular organisms appeared on Earth and the diversity and complexity of life increased dramatically.) Say, “At the end of the Cambrian period, there was a mass extinction of many different species of organisms. Why do you think the octopus and other cephalopods such as the squid were able to survive the extinction?” (Accept various responses.)
Write the following list on the board, saying the items out loud:
o can change color quickly to hide.
o can disappear in a cloud of dark ink that they release.
- Can change body shape.
- Can squeeze through small openings.
- Can live in all oceans of the world (tropics to poles).
- Have great eyesight.
- Can swim quickly.
Have students use the list to generate three examples of stimulus-response for octopuses. Ask students whether the behaviors from the list are learned or innate. (They are all innate.)
Tell students, “All of multicellular organisms you have learned about in this unit can respond to the environment. What about the tiny pond organisms you looked at under the microscope–what are some ways they respond to the environment?” (Accept all reasonable responses.)
Have students work in small groups to design an experiment to test how a microscopic pond organism responds to its environment. Ask each group to write a hypothesis first, by filling in the blanks in the following prompt: “If we change the environment of the (name of organism) by (stimulus), then it will respond by (response).” Check each group’s hypothesis, and then have them describe in paragraph form how they would test the hypothesis in an experiment.
Have students answer the following questions:
1. “What do you think would happen to animals if the amount of oxygen in the Earth’s atmosphere increased? What about plants?” (Answers will vary.)
2. “What do you think would happen to animals if the amount of oxygen in the Earth’s atmosphere decreased? What about plants?” (Answers will vary.)
Conduct a brief interactive activity online. This activity should take about 10 minutes to complete. Note: You may have students work at computers, or you may use a projector to demonstrate the activity for the whole class.
Go to the Atmospheric Oxygen activity at www.teachersdomain.org/resource/tdc02.sci.life.oate.oxygen/. Click View, and follow the directions. Answer the following questions as the class does the activity:
1. What happens to the human, cow, and corn when you decrease the oxygen level to 16 percent? (The human can’t breathe well and has a headache, the cow can’t move around much, and the corn can’t grow big so its ears are smaller.)
2. What happens to the human, cow, and corn when you increase the oxygen level to 25 percent? (The human feels dizzy and is hungry but there is no food, the cow dies because there isn’t enough food, and the corn caught on fire and burned to the ground.)
Discuss whether students’ predictions to the initial questions were correct. Remind students that a basic trait of all living things is the ability to respond to changes in the environment.
- Reinforce concepts for students who may need an opportunity for additional learning by having them create a concept map that includes these terms: behavior, stimulus, response, internal, external, instinct, learned, organism.
- Challenge students who might be going beyond the standards to devise an experiment to test how a plant or animal (e.g., bean sprout or snail) responds to a stimulus. The experiment should include a hypothesis and basic procedure.
- For students who may need an opportunity for additional learning, provide reinforcement of the lesson concepts by having them list ways that they respond to changes in their environment (e.g., sweating on a hot day, answering a doorbell or phone when it rings).
- Students who may be going beyond the standards can list materials and write a step-by-step procedure for the experiment they design, instead of writing a paragraph.