Natural Selection (Katrin Kahen)
Title: Natural Selection
Principle(s) Investigated: Natural Selection - Survival of the Fittest
Standards : Past in the appropriate California content standards.
California standards:
7th Grade Science Content Standards:
- 8a. Students know both genetic variation and environmental factors are causes of evolution and diversity of organisms.
- 8b. Students know the reasoning used by Charles Darwin in reaching his conclusion that natural selection is the mechanism of evolution.
9th - 12th Grade Biology/Life Sciences Content Standards:
- 7a. Students know why natural selection acts on the phenotype rather than the genotype of an organism
- 7b. Students know variation within a species increases the likelihood that at least some members of a species will survive under changed environmental conditions.
Materials: newspaper full length, newspaper, white, and orange (or any other color than newspaper) cut-outs with sides 1cm, times-watch, students as birds use thumb and index finger of non-writing hand.
Procedure: Give a detailed explanation of the procedure and include diagrams if possible.
- As a group, decide which colors will be your camouflaged insects and which colors will be your uncamoflaged insects.
- Insect keepers place 10 camouflaged and 10 uncamoflaged insects of various types on the board without the birds watching.
- Keepers get ready to time 5 seconds.
- The first bird is called over and opens his/her eyes when the insect keeper says “Go!”
- The bird must use the thumb and index finger of his/her non-writing hand to capture one insect at a time.
- Each insect is dropped into a container at the side of the board.
- When the time is up, the recorder counts the number of prey of each type and calculates the surviving population for each type.
- Each surviving insect type breeds to triple its population number before the next bird attack, so insect-keepers add the appropriate number of insects of each type to the board. Rearrange the insects each time so that they are mixed up.
- Call over bird number two and play the game again.
- Call over bird number three and play the game again.
- Play the game for a maximum of six bird attacks or until there are no insects of one type left.
Click here for graph paper.
Student prior knowledge: What prior concepts do students need to understand this activity?
Variations exist within any populations: individuals in a certain population have variations.
Explanation: Give a thorough explanation of the experiment or demonstration. Your explanation should be written to give your fellow teachers a solid understanding and include greater detail than what you might provide for your secondary students. Make certain to include equations whenever pertinent.
A population of “insects” is given to students. Within the population students should notice variation or several different colored “insects.” The camouflaged insects resemble the environment (newspaper) and the un-camouflaged insects are different colors than the environment. Biologists consider natural selection to be the mechanism of evolutionary change and the process responsible for the diversity of life on earth. In this investigation, students will model the process of natural selection for one organism. The students will construct a population graph for each of the two colors of insects. The graphs should include a key. The independent variable is number of generations. The dependent variable is the insects (camouflaged/un-camouflaged) to understand that the independent variable causes a change in dependent variable. Usually, the camouflaged insects survive and reproduce in the next generation. This is “survival of the fittest.” The insects happen to have the trait to survive (blended with the environment) and reproduce. The most adapted insect is the “fittest” one to survive and pass-on the heritable trait to the next generation.
Questions & Answers: Give three thought-provoking questions and provide detailed answers.
1. How would you describe the principles of natural selection?
- In nature, there is tendency toward over-production.
- Not all offsprings that are produced will survive. Resources are limited in the habitat or the environment.
- Variations exist in any population.
- Variations are inherited.
- Those individuals with variations that are suitable for their environment will live longer and leave more offspring on average.
2. Are evolution and survival of the fittest the same thing?
They are connected to each other but nit the same thing. Evolution means change over time or "descent with modification." It is a change in gene frequency over time. For example, the study of fossil records, comparative anatomy, embryology and biochemistry, and genetics provide evidences of evolution. Whereas, survival of the fittest refers to the mechanism - natural selection, that brings about change.
3. How could natural selection work against the survival of an organism?
Natural selection is not the strongest or the smartest to survive and reproduce. The organism happens to have the trait to survive within the population. For example, the male peacock elaborates colorful and beautiful tails to attract mate and sexually reproduce. However, this heritable structural trait makes the male peacock more visible for the predators to prey on. The male peacock happens to have the trait to reproduce and pass on his genes to the next generation in which natural selection selected for this trait. At the same time, the male peacock is more visible and likely to be attacked by predators.
Applications to Everyday Life: Explain (don't just list) three instances where this principle can be used to explain other phenomenon.
One example of evolution and natural selection is the comparison of DNA. Comparisons of DNA nitrogen based sequences show that chimpanzees are more closely related to humans than to gorillas or other apes.
Another example is rapid evolution 1. The reaction of bacteria to penicillin often results in rapid evolutionary change. 2. When penicillin is added to bacteria in a culture dish, a clear zone forms indicating death of the bacteria in that zone. 3. Those few bacteria with a gene for penicillin resistance will survive and go on to reproduce (thus, the group of bacteria has evolved). 4. The organisms that continue to live and reproduce after the change in the environment are adapted to the new environment.
Photographs: Include a photograph of you or students performing the experiment/demonstration, and a close-up, easy to interpret photograph of the activity --these can be included later.
Videos: Include links to videos posted on the web that relate to your activity. These can be videos you have made or ones others have made.