Grade 12 U Homeostasis

This resource page is designed to help students respond to STSE issues relating to ‘Homeostasis’ with inquiry-based actions. ‘Homeostasis’ is a unit set within Ontario’s Grade 12 Biology curriculum. The Overall Expectations for teaching and learning in this unit are:
1. Describe and explain the physiological and biochemical mechanisms involved in the maintenance of homeostasis
2. Analyze, through experiments and the use of models, the feedback mechanisms that maintain chemical and physical homeostasis in animal systems
3. Analyze how environmental factors (physical, chemical, emotional, and microbial) and technological applications affect/contribute to the maintenance of homeostasis, and examine related societal issues

General Overview of Resources Use
The activities of this resource page are organized into three progressive sections as recommended in the Backgrounder.
Click here for a brief description of the sections.

Detailed Suggestions for Resources Use
1. Model Inquiry-based STSE Actions
You could begin by engaging students in a discussion on what homeostasis is and why it is important, and provide examples of homeostatic mechanisms (e.g. hairs on arms and legs stand up, blood vessels contract, muscles contract (shiver), and metabolism increases in response to a cold environment). Afterward, you could have students consider different factors that would affect the balance of a person's internal environment and identify ones that are a result of technology, society and/or environment. You might also introduce the following STSE issues:
Birth control pills: The "pill", which contains a combination of estrogen and progesterone, prevents conception by blocking ovulation and thickening mucous in the cervix, which makes it difficult for sperm to travel through. The changes in hormone levels may result in side effects such as nausea, weight gain/loss, breast tenderness, mood changes, and more. In addition, birth control pills do not protect against sexually transmitted infections.
Stress: Cortisol – a hormone which helps provide bursts of energy, increased immunity, heightened memory, and lower sensitivity to pain – is released in response to stress. Prolonged and higher levels in the bloodstream, however, are associated with negative effects such as hyperglycemia, decreased bone density, higher blood pressure, lowered immunity, and increased abdominal fat. In our current, high-stress culture, people need to find ways to relax the body and mind.
Steroids: Anabolic steroids are synthetic derivatives of the hormone testosterone. Similar to the male hormone, they help build muscle mass but also have undesirable psychological (e.g. depression, irritability, aggression) and physical side effects (e.g. acne, liver damage, clotting disorders, elevated cholesterol levels). Although steroids are banned by major sporting bodies, athletes (and "regular" people) continue to use them to improve their performance and image.
Chemicals in cosmetics: The cosmetics industry is self-regulated; cosmetics companies are not required to submit safety data to the FDA. Many products (e.g. toothpastes, lotions, shampoos, perfume/cologne) contain harmful ingredients, including carcinogens and toxins. Long-term exposure to such ingredients could contribute to cancer, reproductive toxicity, allergies, endocrine disruption, irritation, and more.
Agricultural pesticides: Insecticides are chemicals designed to kill insects; they enter our bodies when we consume fruits and vegetables that are sprayed with them and are stored in our fat cells. They accumulate in our tissues overtime and are linked with health problems such as cancer, nerve damage, birth defects, infertility, and general hormonal imbalance.
Having sensitized students to a number of issues related to Internal Systems and Regulation, ask students what could be done about them – record their answers. Furthermore, provide examples of actions people have taken through the videos below. After watching each video, allow students to share their reactions.

1) Expert advice on choosing fruits and vegetables

2) Suggestion on how to wash pesticides off of produce

3) Group protests strawberry pesticide

4) Press conference on human experimentation of pesticides

Discussion Questions:
- What is the issue(s) presented in the videos? Who is the targeted audience for each?
- Which video is the most informative for your own action? Explain.
- What sources of information (do you think) were utilized to make the videos?

2. Guided Inquiry-based STSE Actions
Students will become more aware of the many potentially dangerous chemicals that are found in personal care products they use on a daily basis. Show students "The Story Behind Cosmetics" video (below) to introduce the topic.

Part 1 - Personal care products at home
Have students...
a. Identify some of the harmful chemicals cited in the literature, reasons for concern (especially as they relate to homeostasis), prevalence in cosmetics industry, and regulation laws.
b. List all the names of toiletries and cosmetics found in their homes.
c. Visit the Environmental Working Group’s cosmetics database. Using the search option, find the safety ratings for their list of toiletries and cosmetics – record them beside each product. (The database provides a numerical ratings for commercial products from 0-10, which is an accumulated score based on the safety of individual ingredients. Note: the database does not list every product on the market.)
d. Graph the number of products found under each safety rating category: low hazard (0-2), moderate hazard (3-6), and high hazard (7-10). Students' graphs might look like this: Safety Ratings of Household Toiletries.doc.
*A variation of the activity would be to graph the safety ratings of a) a particular type of personal care product such as commercial body washes OR b) products from a particular brand such as Aveeno.

Part 2 - Correlational study of personal care products
Have students...
a. Brainstorm factors that may affect the safety ratings of cosmetics. Examples of factors include:
- Price/brand of shampoos
- Marketed gender of hair gels
- Body part (hair vs. skin vs. mouth products)
- Certified organic label
b. Choose a factor to study (e.g. marketed gender of hair gels); identify and categorize products according to that factor (e.g. male and female hair gels).
c. Find and record the numerical safety rating of each product from the Environmental Working Group's cosmetic database.
d. Graph the average numerical safety rating (0-10) for each category. See sample graph.
*A variation of the activity would be to look at the proportion of products that contain a specific chemical linked to cancer as the dependent variable, rather than Environmental Working Group safety ratings.

Part 3 - Critical analysis of Environmental Working Group (EWG) cosmetics database
With vast amounts of information readily available through the Internet, it is important for students to critically examine presented information and identify factors that may affect its validity or accuracy. Ask students to think about some of these factors; in your discussion, you may want to bring up social influences on science and technology.

The questions below are for students to consider the trustworthiness of the information provided by the EWG cosmetics database. Students will need to visit the EWG Homepage for the first two questions.
i) Who is on the EWG board and staff? What are their credentials and affiliations?
ii) Who funds the EWG? Are there competing interests between the EWG and their funders? Where do their funds go?
iii) How are the overall safety scores determined for products in the cosmetics database? The overall safety score of a product is based on the safety scores of the product's individual ingredients but is not an average of the individual scores.
iv) What are the safety scores for individual ingredients based on? The results of one or more scientific studies. Is there adequate evidence to support each score? Some evidence provided is general and not directly linked to disease. For example, the website says sesamum indicum is linked to cancer because "one or more in vitro tests non-mammalian cells show positive mutation results." First of all, the tests were not conducted on human cells or within a living system. Furthermore, positive mutations do not necessarily mean cancer and the statement doesn't indicate how serious the mutations are.
v) Is the information presented in the database adequately referenced? Direct references are not provided. How would you rate the quality of sources of information (i.e. do they use more primary or secondary sources)?
vi) Based on the questions above, how valid is the information in the EWG cosmetics database? What improvements would you suggest? Is the database a valuable resource – why or why not?

Part 4 - Create and implement a plan of action
Using knowledge from primary and secondary research, have students implement actions to address the issue of daily exposure to harmful ingredients found in personal care products.

Recommended websites:
Safe Cosmetics
Canadian Cosmetic, Toiletry and Fragrance Association
Cosmetics and Personal Care (Health Canada)
Cosmetic Ingredient Review

3. Student-led Inquiry-based STSE Action Project
a. Handout copies of the assignment to the class – it may be useful to do this at the beginning of the unit. Read it over together and ensure everyone understands each part.
b. Provide students with a list of STSE issues relevant to the Internal Systems and Regulation unit, including ones that were brainstormed by students in the first, modeling activism phase.
c. Organize students into small groups of 3-5 students – each will explore and act upon one STSE issue. Encourage students to work collaboratively, making decisions and dividing work appropriately.
d. Provide students with in-class time to use the library and/or computer lab for research and encourage groups to meet outside of class time. It would also be useful to set tentative deadlines for each stage of the project to help groups manage their time.
e. Towards the end of the unit, students should have an opportunity to defend their proposed actions with their research findings in front of the class. This would provide a great opportunity for students to share their learning with the class, reflect upon their growth and next steps, and receive feedback from the teacher and peers.