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May 28, 2018 | by  | in News | [ssba]

How Did Prehistoric Plankton Die? Scientists Check the Orbit-uaries

A research team at Victoria University has uncovered a link demonstrating how Earth’s orbit and motion had an effect on the evolution of life. Their approach brings together techniques from geology, biology, and astronomy to give scientists a better picture of the history of life on our planet.

Professor James Crampton and his research team in the School of Geography, Environment and Earth Sciences traced the evolution and extinction rates of an extinct species of plankton called graptoloids, which once lived in Earth’s oceans between 480 and 430 million years ago.

The history of the graptoloids are one such record of how life could have been affected by changes in the position of Earth’s axis and its distance from the sun. It is mathematically impossible for astronomers to calculate changes in the planet’s orbit further back than 50 million years due to chaos theory, but the effects of those orbital changes can be reflected in the development of life on Earth and examined in fossil records.

During the time the graptoloids were alive — 450 million years ago — Earth had undergone a mass extinction event, when large sums of the planet’s biodiversity suddenly died off.

“[T]he relationship between these orbital changes and extinction has never been shown before in truly ancient ecosystems,” says Professor Crampton.

“There’s a strong debate in science about the impact on extinction and evolution of environmental change versus interactions between species (such as competition for food). With this study we can provide evidence of the impact of environmental changes on life on Earth.”

Crampton noted that the next step in this research would be to determine what specific events on Earth occurred to cause the extinction events as a result of the changes in planetary orbit.

“We also want to look more closely at what happens after a species becomes extinct. We know that when a species becomes extinct, a new species will evolve to take the place of the extinct species in an ecosystem, but we don’t know how long that takes.”

Plankton are a vital part of the ocean’s food chain, and the world’s ecosystem overall. Plant-like phytoplankton play a role in Earth’s carbon cycle, absorbing carbon dioxide from the atmosphere and producing the oxygen we breathe in the same manner and scale as forests. Studies of plankton populations can serve as an indicator of the environmental health of the planet.


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