4. DNA Models

DNA structure: click on the image to see it rotateDNA structure: click on the image to see it rotateIn this activity, students “discover” the structure of DNA by playing with puzzle pieces representing the component pieces of the DNA molecule: the sugar deoxyribose, phosphate groups, and the 4 nucleic acids (adenine, thymine, cytosine and guanine). The process the students go through in putting the puzzle together resembles the way James Watson and Francis Crick deduced the molecular structure of DNA by manipulating molecular models of the component pieces (and a heavy reliance on the prior experimental work of Rosalind Franklin, Maurice Wilkins, and Erwin Chargaff). The model created by the students makes a lovely classroom decoration and reference for discussing DNA replication, transcription and translation.

3. DNA Extraction

Strawberry DNA: The cloudy substance in the upper layer is strawberry DNA.Strawberry DNA: The cloudy substance in the upper layer is strawberry DNA.Summary
What is DNA? What does it look like? In this activity, students extract DNA from strawberries using diluted dish soap and alcohol. Suddenly this mysterious secret of life can be seen materializing out of strawberry juice right in front of students’ eyes. The long tangled DNA strands that ultimately form may be collected using a bamboo skewer or glass stirring rod. The DNA may even be saved in a necklace made from an eppendrof tube, alcohol and string.

2. Making Babies

This is an extension of the Human Traits survey activity designed to introduce students to genes, genotypes, and simple inheritance patterns. Using information from the Human Traits Survey, students make guesses about their own genotype, create gametes from their genotypes, then make “babies” with a partner. Along the way students discover answers to the questions: What are genes? How are genes (and traits) passed on? How are gametes different than other cells in our body? Why do I look like mom in some ways and dad in other ways and neither of them in still other ways? Why don’t siblings look alike?

1. Human Traits

Genes and DNA are very abstract concepts for students. In order to "hook" them in, I open my genetics and evolution unit with human genetics, specifically looking at the variations in human traits. This allows students' natural curiosity about their identity to draw them into the study of heredity. There are lots of great single gene traits with simple dominance inheritance patterns to explore: earlobe attachment, tongue rolling, cleft chin, etc. There are some polygenic traits that can be explored: hair color, eye color, reach, reaction time, etc. Hair texture (curly, wavy, vs. straight) offers a good example of incomplete dominance. After collecting information from themselves and two others, the population data is collected on several large charts in order to look for and discuss the patterns.

Genetics Box

This box hooks students into the study of genetics by investigating the inheritance of human traits. Drawn by students' natural curiosity about how they come to look the way they do, they learn the basics of Mendelian genetics. From this introduction, students extract DNA, build DNA models and use them to study replication, transcription and translation.

Exploratorium Box

This megabox contains teaching boxes created by the fabulous teachers of the Exploratorium Teachers Institute. What is a teaching box? It generally takes the form of a cardboard box in a science teacher's classroom or garage. Inside you will find the collected materials, lesson plans, background information and ideas needed to teach a set of lessons on a certain topic.

8. Dinosaur Extinction Theories


Cartoon by Chris Madden

Ark cartoon - Chris MaddenWhat caused the extinction of the dinosaurs? Was it a massive meteor? Was it the result of tremendous volcanic activity that covered the globe in volcanic ash? Was it the effects of gradual climate change? Was it the result of plate tectonics? Students are given a set of evidence cards that state scientific discoveries about rocks from 65 million years ago and prediction cards that discuss the predicted effects of different events such as a meteor impact, a rise in carbon dioxide levels, and plate tectonics. Teams of students are charged with assembling this information into an overarching theory that best explains the evidence at hand. At the end of the period or the following period, teams present their theories to the whole group and enter into a debate about the cause or causes of the great dinosaur extinction.

Can sort through evidence and come up with a scientific theory that best fits the data.
Can recognize whether evidence is consistent with a scientific theory.
Can use geologic evidence to propose theories about past life on earth.

7. Choose Your Own Fossil Adventure

Fossils are extremely rare but also extremely exciting and rich with information about past life on Earth. In this lesson, students learn about the major types of fossils and how they form. They complete the lesson by illustrating and creating a “Choose Your Own Adventure” type story in which a Tyrannosaurus rex dies with 7 different possible endings, only one of which results in the discovery of its fossilized skeleton.

6. Geologic Timelines

For students, a few days can feel like a very long time. Thus, my students have a hard time conceptualizing the difference between 1 thousand, 1 million and 1 billion years. In this activity, students develop a sense of just how long the geologic time scale really is by creating a to-scale geologic timeline. This lesson begins with students guessing how long ago different events happened – when the Earth was formed, when life began, when dinosaurs roamed, and when humans first appeared. Then students redraw the periods and eras of the Phanerozoic Eon to scale using adding machine tape (1 million years = 1 millimeter). Then a teacher created scroll containing the other eons: Proterozoic, Archean and Hadean is unrolled to give students a visual sense of just how long Earth history really is. Finally, there are some analogies for students to contemplate, such as when different events would have occurred if Earth history were condensed into a calendar year or into a cross country trip.

5. Geologic TIme on the Web

The University of California Museum of Paleontology (UCMP) created a fabulous introduction to the geologic time scale on the web called “Understanding Geologic Time”. Students are led through a series of interactive web pages covering a wide range of earth history concepts: relative vs. absolute time, the law of superposition, radiometric dating, the geologic timescale, and the origins and evolution of life on Earth. While the teacher section includes assessment materials including a “Scavenger Hunt” activity, I have included an alternative worksheet for students to follow as they navigate through the website and some extra credit questions in UCMP’s online “Geology Wing” for students that finish early. Links to activities that teach radiometric dating are included in the Going Further section.