Type of lesson

3. Testing for Life's Molecules

All known life is made out of a small group of chemical compounds called organic molecules. Common organic molecules include proteins, glucose, starch, lipids, and nucleic acids. This lesson plan asks students to conduct tests for proteins, glucose, and starch. At the beginning of the activity, they choose 3 items to test: one known to be “never alive”, one known to be “once was alive”, and one mystery item. In addition, each station includes a positive control. By the end of the experiment, students should be familiar with some of the major organic molecules and should recognize that living things, and substances derived from them, are made of organic molecules. In addition, this is a chance to bring in topic surrounding nutrition, health, and digestion. Since our bodies are made up of organic molecules, we need each of these molecules as nutrients in our food.

2. Life Traps

Life trapsLife trapsAs part of recognizing the characteristics of life that all organisms share, students grow microbes on nutrient agar plates. Students swipe surfaces with a sterile Q tip swab and seed plates resulting in a wide range of colorful and prolific bacteria and fungi colonies. Other plates may be simply opened to the air to catch life floating in the air. Through these experiences, students learn that all living things, even those so small and invisible as to be floating in the air, grow and reproduce when provided with the proper nutrients and water. Teachable moments abound since the “dirtiest places”, like the toilet rim, often result in the least bacterial growth while presumably “clean” places, like the surface of your skin, have the most. A fun extension of this activity (see the Going Further section) is to start a sourdough culture from wild yeast in the air and make sourdough bread.

1. Is it alive?

What does it mean to be alive? Is a cactus alive? Is a seed alive? Is the air we breathe alive? What are the necessary characteristics? To hook students into the question, they are introduced to “glue monsters” (sometimes known as “scooting glue”) and the class discusses whether the “monsters” are alive or not. Next, students are given cards with the names of various objects and asked to sort them into categories: alive, once was alive, never alive, and not sure. Finally, students create a list defining the characteristics of life – a set of characteristics that all living things share. The list is initially developed in pairs, then in larger groups of 4, and ultimately as a whole class. The final list is turned into a poster that can be referenced and modified throughout the remainder of the unit as students learn more about what it takes to be alive.

Physiology Box

Physiology is the study of living things – their structure, organization, and biochemistry. This unit gives students an opportunity to discover the fundamental characteristics of living things and explore some basic cell biology. Students begin with several activities culminating in the creation of a list of characteristics that all living things have in common – the characteristics of life list. From here, students learn to test for signs of life by growing microbes on agar plates, conducting biochemical tests, visualizing cells, and experimenting with photosynthesis and respiration. Finally, students learn about the organization plants and animals through dissection and the raising of plants and fish in the classroom. Throughout the unit, students return to the characteristics of life list, refining and revising their list as they learn new concepts. A planning guide for a voyage with the Marine Science Institute is included as a way for students to learn about the many forms of life in the San Francisco Bay.

8. Bird Beak Buffet

Inspired by observations of finches on the Galapagos Islands, Charles Darwin came up with an idea that is perhaps the most influential idea in all of science - natural selection. In this classic activity, students learn about natural selection by becoming birds foraging for food on an island (a large area of the schoolyard or classroom). The prey (beans) vary in their coloration such that some blend into the environment better than others. The birds vary in the type of beak they have (plastic forks, spoons and knives). Each season, any prey that survives has a baby bean the same color as the parent. In addition, the most successful birds has a baby with the same beak trait while the least successful birds die (and are reincarnated as the babies of the successful birds). Over several generations, the bird and bean populations shift depending on the environment. Well camouflaged beans survive and reproduce. Birds with beaks that can easily capture beans survive and reproduce. In this way, students model natural selection in 2 species and get a very good idea of how natural selection works.

Sub Plan - DNA Jewelry

Students create DNA models from beads and wire that may be used as earrings, pendants, Christmas ornaments, and/or key chain pulls. This project is simple enough that a good substitute could lead the students through it since the content should be taught beforehand. More importantly, this is just one of many possible 3D DNA models you could have your students build. Be creative! Use gumdrops, Styrofoam, marshmallows, Legos, grapes, wood, aluminum cans, etc. Better yet, have your students design a model independently.

Real World - Sickle Cell Anemia

Sickle Cell Anemia
Sickle-shaped red blood cellsSickle-shaped red blood cellsSickle cell disease is a disorder that affects the red blood cells. Red blood cells use a protein called hemoglobin to transport oxygen from the lungs to the rest of the body. Normally, red blood cells are round and flexible so they can travel freely through the narrow blood vessels.

Patients with sickle cell disease have a mutation in a gene that codes for part of the hemoglobin protein. As a result, hemoglobin does not form properly, causing red blood cells to be oddly shaped. These irregularly shaped cells get stuck in the blood vessels and are unable to transport oxygen properly, causing pain, frequent infections, and damage to the organs. Patients with sickle cell disease only survive to be 20 to 30 years old. About 1 in 500 babies born in America has the disease.

The normal hemoglobin nucleic acid sequence looks like:

Real World - Cyctic Fibrosis

Cystic Fibrosis
Cycstic fibrosis breathing apparatusCycstic fibrosis breathing apparatusCystic fibrosis is a genetic disease that affects many different parts of the body. There are approximately 30,000 Americans with cystic fibrosis. The most serious problem is the production of extremely thick, sticky mucus that clogs up the bronchial tubes in the lungs and the passageways in the pancreas (remember, the pancreas makes digestive juices that help break down food). This causes malnutrition, diabetes, lung infections, and difficulty getting enough oxygen to the body. Most people with cystic fibrosis die in their 20s or 30s from lung failure.

Assessment - Real World Problems

The following are a series of real world genetics problems that relate to the genetic disorders cystic fibrosis and sickle cell anemia. They may be used to give students practice with Mendelian genetics and molecular biology or at the end of the unit to assess their understanding of various concepts.

Reinforce and assess students understanding of real world genetics issues.

Project - Dragon Genetics

In this long term computer based simulation, students play with a fabulous FREE software program called Biologica developed by the Concord Consortium. It offers an in depth, virtual experience exploring Mendelian inheritance patterns in dragons. Activities increase in complexity from initial modules introducing dragons and their chromosomes to later activities that require problem solving skills and the integration of many levels of prior knowledge. In the program, you can manipulate dragon chromosomes, breed dragons, explore pedigrees, and more. There are fantastic puzzles along the way: Which gametes should you select to breed a purple, fire breathing, boy dragon? What happens if you change the DNA sequence? Can you figure out the genotype of invisible dragon parents from the phenotypes of their offspring?