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Biology/What types of organic matter comprise oil?


I am an artist and I have been working on a complex drawing which begins with the protocell and moves out through evolution into more and more complex life forms. I was thinking about its purpose and meaning and thought it would be much more potent if what I am drawing is the lifeforms that are compressed over time and become oil. I have been doing some research online to find out if I can fit what I have draw so far into this concept, but I have been getting conflicting answers.
I have read that oil is made from single celled aquatic plants and animals, mainly from seas but sometimes from swamps as well.
I have drawn many more complex multi cellular plants and animals. Is is likely that bit and pieces of these animals fell to the bottom of the ocean as marine snow and were also compressed into petroleum?
What about land plants and animals. I know that coal is formed mainly from the woody parts of trees, but is it possible and pieces of trees or land animals ended up in swamps or in rivers and carried to the sea.
I have read conflicting things about the time period that oil is from. One website said that the plants and animals that comprise it are at least 300 million years old, where as another site said that it is 70% mesozoic era life forms.
As of right now I have draw up to the permian era. I have included Synapsid and Diapsid reptiles as well as beetles and flying insects, ginkgoales and conifers.
Is it wrong to assume bits and pieces of these lifeforms could also also contribute to the matter that turned into oil?
Thank you so much for your help!

There are still questions about the origin of gas and oil but here is what most geologists believe.
Oil and gas are of an organic origin involving the fossilization of plants and animals.
They were formed during the carboniferous period between 360 and 200 million years ago.
Coal was formed from plant remains and oil from both plants and animals.
I have never seen evidence that oil came from single celled organisms although the most common algae ,the diatoms, do contain droplets of oil.
There is also an idea that oil has an abiotic origin and formed from non-living materials. This is based upon the fact that Saturn and it's moons have Methane (CH4)



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Walter Hintz


Science teacher for over 50 years. MSc. in biology. I can answer questions in general biology, zoology, botany, anatomy and physiology and biochemistry.


I have a MSc in biology and have been a science teacher for over 50 years. At present I am a faculty member at a college and a science consultant at seven catholic schools.

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