A female giraffe walks up to a tree with leaves just out of reach. She lifts her head and stretches her long neck, barely reaching the green leaves of the tree. As she eats more and more leaves off of tall trees, her neck seems to have grown a little bit longer. This giraffe is pregnant with a baby giraffe. When the baby grows to be full size, will it have a longer neck because the mother giraffe stretched so much?
Let’s picture a different scene now. Think about a forest filled with trees that have light-colored bark. The air pollution in the area gets bad over time, and the color of the tree bark starts changing from light to dark. Suddenly, light moths that were previously camouflaged are now easily found by birds. Will light moths be common in the next generation?
These examples all focus all relate to the same main questions: How is a trait passed to an organism’s offspring and how does it spread through a population?
This week, you will discuss ideas of natural selection with your class, play a selection-based game, and take a trip through time to see how scientists of the past figured out just how a trait is passed from a parent to its offspring.
What You Need
- PowerPoint presentation (your teacher has this)
- One pre-lesson quiz
- Post-lesson quiz
- In-class worksheet
- Pen or pencil
If you are completing the rice activity, you will also need:
- Light and dark bark (or crumpled light and dark construction paper)
- Small bag of wild rice
- Small empty bag
- Forceps (like tweezers)
- Timer or stopwatch
If you are completing the moth hunting activity, you will also need:
- Access to a computer
Before You Begin
The very first thing you should do is answer all the questions on the pre-lesson quiz. This one has PRE written in the top corner. Don’t worry, this first one is not for points! When you’ve completed the quiz, make sure your name is on it and turn it into your teacher.
ENGAGE: Giraffe Example
1. Look and listen closely to the pictures and presentation shown by your teacher. Follow along with the presentation, thinking about the pictures and questions presented and discussing them with your classmates.
2. After you and your class have finished talking about the giraffe’s traits and how they developed, discuss this hypothetical situation:
Imagine two pairs of giraffes: one pair with a male and female that eat only from the tops of tall trees, and one pair that eats from the lower branches of trees.
3. Listen to the rest of the teacher’s presentation. Then, pick one of the following questions and write the question and your answer on your classroom worksheet. This is individual work, do not work in groups.
- How did giraffes as a species get such a long neck?
- Will giraffe babies be similar or different than their parents? Why?
- How are traits, such as a long neck, passed down from parents to offspring?
4. Discuss your answers as a group and explore how these ideas might apply to birds with different sized beaks.
EXPLORE: Computer Simulation OR Rice Activity
If using the computer simulation, follow these directions:
5. Open the game and click on the bird icon (bottom middle) to play “bird’s eye view” of selection. Read the instructions and play a game in the light forest. Record your results on the classroom worksheet.
6. Revisit the bird icon and play a game in the dark forest. Record your results on the classroom worksheet.
7. After you’ve played in both the light and dark forest, click on the power plant icon (top middle) to learn about the background for the game you just played.
8. Click on the black and white moths icon (top right) to visit an explanation of Dr. Kettlewell’s experiments. Read through the explanation of his experiments and predictions.
9. Skip down to step number 13, below.
NOTE: If you need the Flash version of the game, click here.
If using the rice activity, follow these directions: