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Today students had their Evolution symposium and used different evidences of evolution to explain how they arranged the different organisms on their Phylogenetic Trees from yesterday. Some students presented their findings to the class and we ended our symposium with a reception with cookies and drinks as we discussed our learning. There are as many ways to categorize animals as there are animals themselves. However, in biology some ways give us a better understanding of relatedness among animals. Homologous structures and DNA similarities are clear evidence of common origins among animals. Analogous structures and geographic speciation are ways we can establish differences among organisms. All of these tools help us understand the tree of life, with all living organisms sharing a singular origin, that has been branching into more and more complex organisms over the last 3.5 Billion years! As with all good science projects, once we collected our data, we took the time to analyze it. Using Google sheets, we graphed individual class results for the number of different birds over time. And although the trends were similar across classes, each class also showed unique patterns. However, when all class data was graphed together (96 data points!) overall trends became very clear.
Surprisingly, both Small and Medium beaked Clipbirds had the greatest success in both survival and reproduction, as well as a fairly direct relationship between time and population. Big beaked birds however, in contrast to many students hypotheses, always struggled to survive and almost never reproduced on the island due to their vastly higher calorie requirements. In this activity it became very clear that natural selection does not always favor the biggest, or strongest animal but always the animal best adapted to its environment, which on Clipbird island meant having a small or medium beak, intsead of a big beak. Tuesday when we get back to school we will continue looking at evolutionary relationship among not just small groups of organisms but of many organisms across the tree of life. Today's class was all about Natural selection. Students spent the period as "ClipBirds" trying to survie on the island of New ClipLand. Clip Birds only sources of food are popcorn kernels, Lima beans, or marbles. The goal of the game is survive and to reproduce. The more food you eat the better chances you have of survival and having offspring. However, the more ClipBirds enter the game, the more competition there will be for the limited resources. There are three types of ClipBirds, Big Beaked, Medium Beaked, and Small Beaked. Every time a ClipBird Reproduces there's a 1/3 chance a mutation occurs, which causes the offspring beak to either be bigger or smaller than their parents. This game highlights a lot of different concepts in ecology and evolution including natural selection, limiting factors, carrying capacity, as well as positive, negative, and neutral mutations. A version of ClipBird Island is attached below: Bonus Gold Tape Question: Anyone that emails or gives Mr. Powell a written response to this Question by neat Friday, October 20, by the end of class will get a piece of Gold Tape: Explain how our game ClipBird Island demonstrated all three ecology and evolution concepts of natural selection, limiting factors, and carrying capacity.
Today we finished up our study of fossils. Some of the conclusions we came to are that fossil teeth tell us a lot about not only what an animal ate but also about the type of environment it may have lived in. In fact, a famous french scientist, Georges Cuvier, even once declared that given a single tooth, he could describe an animals entire skeleton. Teeth are among some of the most important fossils paleontologists can study and tell us enormous amounts of information about the past history of earth. After wrapping up our discussion of fossils, we played "The Chaos Game." In the chaos game students use dice to randomly place dots on a triangle and after many many trials, a pattern will emerge. The triangle they create is called a Sierpinski Triangle and is a great metaphor for evolution, or simply, given a definite set of rules, random events over time will create patterns. Below you can watch a video of a computer simulation creating a Sierpinski Triangle the same way we did in class.
We have finally finished our genetics unit and are moving on to Evolution. Today students took an evolution pretest to see what they know and what they remember about natural selection, adaptations, and evolution. And then we really started our unit with a webquest about geologic time and the history of life on earth from the University of California Museum of Paleontology. Click the picture to the right to go to the webquest. If you need the worksheet that goes with this activity you can download the file below.
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AuthorMr. Powell is a High School Science Teacher in Western Colorado. Archives
May 2024
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