Instructions
Read the information below about thrombolites, which are fascinating structures built by microbes. After reading, complete the activities to test your understanding.
Reading: The World of Thrombolites
Thrombolites are special types of rock-like structures built by communities of microscopic organisms, primarily cyanobacteria. These structures are a type of microbialite, which is a general term for any geological structure formed by the trapping, binding, and mineral precipitation activities of microbes. Thrombolites are often called "living fossils" because they are formed by the same processes that created some of the earliest evidence of life on Earth, dating back billions of years.
The name "thrombolite" comes from the Greek words thrombos, meaning "clot," and lithos, meaning "stone." This name perfectly describes their most important feature: a clotted, lumpy, and disorganized internal structure. This is the key difference between thrombolites and their more famous cousins, stromatolites. Stromatolites, whose name means "layered stone," have a distinctly laminated, or layered, internal structure. You can think of a thrombolite as a clumpy pile of granola, while a stromatolite is more like a stack of pancakes.
The microbes that build thrombolites, like cyanobacteria, perform photosynthesis. This process was crucial for early Earth, as it released massive amounts of oxygen into the atmosphere over millions of years, paving the way for more complex life to evolve. Today, living thrombolites are very rare. One of the most famous and important locations where they can be found is Lake Clifton in Western Australia. Studying these modern thrombolites gives scientists a unique window into the deep past of our planet.
Activity 1: Vocabulary Match
Match the term on the left with its correct definition on the right. Write the letter of the definition in the blank space.
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1. ___ Thrombolite 2. ___ Stromatolite 3. ___ Cyanobacteria 4. ___ Microbialite 5. ___ Clotted 6. ___ Laminated |
A. Arranged in thin layers or sheets. B. Photosynthetic bacteria that are the primary builders of thrombolites and stromatolites. C. A microbialite with a layered internal structure. D. A general term for a rock-like structure built by microorganisms. E. A microbialite with a lumpy, non-layered internal structure. F. Having a lumpy and disorganized texture. |
Activity 2: Short Answer Questions
Based on the reading, answer the following questions in your own words.
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What is the main physical difference between a thrombolite and a stromatolite?
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Why are thrombolites sometimes called "living fossils"?
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What critical role did the microbes that form thrombolites play in the history of Earth's atmosphere?
Activity 3: Fill in the Blanks
Complete the following paragraph using words from the word bank below.
clotted layered oxygen cyanobacteria microbialites stromatolites
Thrombolites are a type of , which are structures built by microbes like . These ancient organisms changed the planet by releasing into the atmosphere through photosynthesis. The key feature of a thrombolite is its internal structure, which is and lumpy. This makes them different from , which have a distinctly internal structure.
Answer Key
Activity 1: Vocabulary Match
1. E - A microbialite with a lumpy, non-layered internal structure.
2. C - A microbialite with a layered internal structure.
3. B - Photosynthetic bacteria that are the primary builders of thrombolites and stromatolites.
4. D - A general term for a rock-like structure built by microorganisms.
5. F - Having a lumpy and disorganized texture.
6. A - Arranged in thin layers or sheets.
Activity 2: Short Answer Questions
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What is the main physical difference between a thrombolite and a stromatolite?
The main difference is their internal structure. Thrombolites have a clotted, lumpy internal structure, while stromatolites have a layered (laminated) internal structure. -
Why are thrombolites sometimes called "living fossils"?
They are called "living fossils" because modern thrombolites are formed by the same types of microbes and biological processes that created ancient fossilized structures billions of years ago. -
What critical role did the microbes that form thrombolites play in the history of Earth's atmosphere?
Through photosynthesis, they released huge amounts of oxygen into the atmosphere, which was essential for the evolution of more complex, oxygen-breathing life.
Activity 3: Fill in the Blanks
Thrombolites are a type of microbialites, which are structures built by microbes like cyanobacteria. These ancient organisms changed the planet by releasing oxygen into the atmosphere through photosynthesis. The key feature of a thrombolite is its internal structure, which is clotted and lumpy. This makes them different from stromatolites, which have a distinctly layered internal structure.