Sea Sponges Soak Up the Glory

SCIENCE

What (doesn’t) live in a pineapple under the sea? The very first animals on Earth, scientists believe. (The Independent)

How do sponges contribute to marine ecosystems? Find out with our illustrated guide!

Scroll down for a quick list of key resources in our Teachers’ Toolkit.

Discussion Ideas

  • According to the good folks at MIT, the earliest sea sponges probably predated the Cambrian explosion. What is the Cambrian explosion?
    • The Cambrian explosion was the relatively rapid development of almost all major types (phyla) of organisms. The Cambrian explosion took place about 542 million years ago, during a Paleozoic time period known as the Cambrian (542 to 485.4 million years ago).

 

 

  • So, scientists studied “molecular fossils.” What are molecular fossils?
    • According to the video, “molecular fossils are trace amounts of molecules that have survived in ancient rock long after the actual animal has decayed.”

 

  • How did MIT researchers use molecular fossils to identify sponges that existed before the Cambrian explosion?
    • Scientists analyzed rocks containing 24-IPC, a lipid molecule related to cholesterol. 24-IPC is produced by both sponges and algae today, but research shows that sponges developed the ability to produce 24-IPC long before algae. In fact, they developed the ability about 640 million years ago—the same age as the rocks studied.

 

  • Does the suggestion of sea sponges being the first animals on Earth come as a surprise to scientists?
    • No, most biologists thought sponges were one of the likeliest candidates for oldest type of animal on Earth. What comes as a delightful surprise is the apparent date of their appearance, much earlier than the fossil record alone suggests. (Take that, stromatolites.)

 

The largest specimen of Caribbean giant barrel sponge (this one is off the coast of Belize) reached over 8 feet! Photograph by Brian Skerry, National Geographic

This beautiful barrel sponge is part of a coral reef off the coast of Belize.
Photograph by Brian Skerry, National Geographic

TEACHERS TOOLKIT

The Independent: Sea sponges were the first animals on Earth, scientists discover

Nat Geo: Coral Reef Food Web

MIT: Title for ‘Earth’s first animal’ likely goes to simple sea creature

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