Why Fossilized Shark Teeth Are Black

Why Fossilized Shark Teeth Are Black Shark teeth are made up of calcium phosphate, which is the mineral apatite. Although shark teeth are sturdier than the cartilage that makes up their skeleton, the teeth still disintegrate over time unless they are fossilized. This is why you rarely find white shark teeth on a beach. Shark teeth are preserved if the tooth is buried, which prevents decomposition by oxygen and bacteria. Shark teeth buried in sediments absorb surrounding minerals, turning them from a normal whitish tooth color to a deeper color, usually black, gray, or tan. The fossilization process takes at least 10,000 years, although some fossil sharks teeth are millions of years old! Fossils are old, but you cant tell the approximate age of a shark tooth simply by its color because the color (black, gray, brown) depends completely on the chemical composition of the sediment that replaced the calcium during the fossilization process. How to  Find Shark Teeth Why would you want to find shark teeth? Some of them are valuable, plus they can be used to make interesting jewelry or to start a collection. Plus, theres a chance youll find a tooth from a predator that lived 10 to 50 million years ago! While its possible to find teeth just about anywhere, your best bet is to search at a beach. I live in Myrtle Beach, so every time I go to the shore I look for teeth. At this beach, most of the teeth are black because of the chemical composition of the sediment offshore. At other beaches, fossilized teeth may be gray or brown or slightly green. Once you find the first tooth, youll know what color to seek. Of course, theres always a chance youll find a white shark tooth, but these are much harder to see against shells and sand. If youve never looked for shark teeth before, start out looking for black pointy objects. If the teeth are black, there will also be some black shell fragments that resemble shark teeth.  How do you know if its a shell or a tooth? Dry off your find and hold it up to the light. Even though a tooth could be millions of years old, it will still look glossy in the light. A shell, on the other hand, will show ripples from its growth and maybe some iridescence. Most shark teeth also maintain some of their structure. Look for a cutting edge along the edge of the blade (flat part) of the tooth, which may still have ridges. Thats a dead giveaway youve scored a shark tooth. A tooth may also have an intact root, which tends to be less shiny than the blade. Teeth come in a variety of shapes. Some are triangular, but others are needle-like. Good places to start are at the waterline, where the waves can help reveal the teeth, or by inspecting or sifting through a pile of shells. Keep in mind, the size of the teeth you can find is usually similar to the size of surrounding debris. While its possible to find a giant Megalodon tooth in the sand, large teeth like this are most often found near similar-sized rocks or shells.

The Purpose of Building a Portfolio Assessment

The Purpose of Building a Portfolio Assessment A portfolio assessment is a collection of student works that are associated with standards you are required to learn. This collection of work is often gathered over a long period of time to reflect what you have been taught as well as what you have learned. Each piece in the portfolio is selected because it is an authentic representation of what you have learned and is meant to demonstrate your current knowledge and skills. A portfolio by nature is a storybook capturing a students progression of learning as they move through the year. What Goes Into a Portfolio A portfolio can include classwork, artistic pieces, photographs, and a variety of other media all demonstrating the concepts that you have mastered. Each item that is selected to go in the portfolio is chosen within the parameters of the purpose of the portfolio itself. Many teachers require their students to write a reflection that correlates with each piece in the portfolio. This practice is advantageous for the student as they self-assess their work and may set goals to improve. Finally, the reflection helps reinforce the concept for the student and it provides some clarity for anyone reviewing the portfolio. Ultimately, the most authentic portfolios are built when the teacher and student work collaboratively to decide which pieces should be included to demonstrate mastery of a specific learning objective. The Purpose of Developing a Portfolio A portfolio assessment is often deemed an authentic form of assessment because it includes authentic samples of a students work.  Many advocates of the portfolio assessment argue that this makes it a superior assessment tool because it is demonstrates learning and growth over an extended period of time. They believe it is more indicative of what a students true abilities especially when you compare it to a standardized test that provides a snapshot of what a student can do on a particular day. Ultimately, the teacher guiding the portfolio process helps determine the purpose of the final portfolio. The portfolio may be used to show growth over time, it may be used to promote a students abilities, or it may be used to evaluate a students learning within a specific course. Its purpose may also be a combination of all three areas. The Pros of Using a Portfolio Assessment A portfolio assessment demonstrates learning over the course of time rather than what a student knows a particular day.A portfolio assessment provides an opportunity for a student to reflect on their learning, to self assess, and to formulate a deeper understanding of the concepts they are learning beyond a simple surface explanation.A portfolio assessment requires a great level of individual interaction between the student and teacher wherein they are always collaborating about the requirements and components going into the portfolio.   The Cons of Using a Portfolio Assessment Developing and assessing a portfolio is time-consuming. It takes a lot of effort from both the teacher and the student and is a demanding endeavor in which you can quickly fall behind.Portfolio assessments are very subjective in nature. Even if the teacher utilizes a rubric, the individualized nature of a portfolio makes it difficult to remain objective and stick to the rubric. Two students working on the same learning standard may have two totally different approaches thus learning may not be the same.