Scientists study organization of life on a planetary scale

ASU scientists study organization of life on a planetary scale
This graph represents the biosphere, ecosystems and individual organisms' biochemistry as connecting molecules participating in shared reactions. It reveals that various scaling laws are common across different levels of biological organization. Credit: Hyunju Kim

When we think of life on Earth, we might think of individual examples ranging from animals to bacteria. When astrobiologists study life, however, they have to consider not only individual organisms, but also ecosystems, and the biosphere as a whole.

In astrobiology, there is an increasing interest in whether as we know it is a quirk of the particular evolutionary history of the Earth or, instead, if life might be governed by more general organizing principles.

If general principles exist that can explain properties common to all life on Earth, scientists hypothesize, then they may be universal to all life, even life on other planets. If a "universal biology" exists, it would have important implications for the search for life beyond Earth, for engineering synthetic life in the lab, and for solving the origin of life, enabling scientists to predict at least some properties of alien life.

Previous research in this area has primarily focused on specific levels of organization within biology such as individual organisms or ecological communities. These levels form a hierarchy where individuals are composed of interacting molecules and ecosystems are composed of interacting individuals.

An interdisciplinary team of researchers at Arizona State University (ASU) has gone beyond focusing on individual levels in this hierarchy to study the hierarchy itself, focusing on the biosphere as a whole. The results of their study have been recently published Science Advances.

"To understand the general principles governing biology, we must understand how living systems organize across levels, not just within a given level," says lead author Hyunju Kim of ASU's Beyond Center and the School of Earth and Space Exploration.

Through this study, the team found that biochemistry, both at the level of organisms and ecosystems, is governed by general organizing principles. "This means there is a logic to the planetary-scale organization of biochemistry," says co-lead author Harrison Smith of ASU's School of Earth and Space Exploration. "Scientists have talked about this type of logic for a long time, but until now they have struggled to quantify it. Quantifying it can help us constrain the way that life arises on a planet."

For this research, the team constructed using a global database of 28,146 annotated genomes and metagenomes and 8,658 catalogued biochemical reactions. In so doing, they uncovered scaling laws governing biochemical diversity and network structure that are shared across levels of organization from individuals to ecosystems, to the biosphere as a whole.

"Quantifying general principles of life—not restricted to a domain on the tree of life, or a particular ecosystem—is a challenge," says Smith. "We were able to do that by combining tools from network science and scaling theory, while simultaneously leveraging large genomic datasets that researchers have been cataloging."

The research team, led by Kim and Smith under supervision of Sara Walker of the ASU School of Earth and Space Exploration and the Beyond Center, also includes Cole Mathis of the Beyond Center and the ASU Department of Physics (now at the University of Glasgow), and Jason Raymond of the School of Earth and Space Exploration.

"Understanding the organizing principles of biochemistry at a global scale better enables us to understand how life operates as a planetary process" says Walker. "The ability to more rigorously identify universal properties of life on Earth will also provide astrobiologists with new quantitative tools to guide our search for alien life—both in the lab on other worlds"

Explore further

Interdisciplinary study finds cell networks seek optimal point between stability and adaptiveness

More information: Hyunju Kim et al, Universal scaling across biochemical networks on Earth, Science Advances (2019). DOI: 10.1126/sciadv.aau0149
Journal information: Science Advances

Citation: Scientists study organization of life on a planetary scale (2019, February 5) retrieved 23 October 2019 from
This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.

Feedback to editors

User comments

Feb 06, 2019
Life as a whole system looks disordered to me (as we see in the figure).
Life decreases entropy locally in order for an organism to grow. But it does so only because of complex pre-existing templates and only at the expense of an even bigger disorder that they cause, by producing waste, nutrients, gases,etc. But these waste become food for other organisms in a constant recycling of nutrients. So chemically speaking, we are ignoring the big chemical picture and we are cherry picking the reactions that look like us, or we consider important, etc and we name them alive.
If we view life as an entire chemical system, life becomes just what we perceive of some regular complex chemical reactions (Any complex process will appear self-organizing to the eyes of the results). Its a self-fulfilling prophecy. This gives a natural explanation because there is no need to wait eons for rare unlikely events to happen, or order to be created and start propagating,etc.

Feb 06, 2019
Life as a whole system looks disordered... Life decreases entropy locally ... because of complex pre-existing templates and only at the expense of an even bigger disorder ... chemically speaking, we are ignoring the big chemical picture ... some regular complex chemical reactions

The point of the paper is that it did not ignore the big chemical picture, yet it found order.

It is a fact that cells work like refrigerators, internally lowering entropy by exporting it (locally, I would add, but of course entropy eventually exports to space). That regularity is evolved homeostasis, which borrow its main feature of keeping a (dis-)equilibrium from Le Châtelier's principle [ https://en.wikipe...rinciple ]. That life likely evolved in such conditions in hydrothermal vents, and rapidly so easily, agree with that it was neither unlikely or had to "re-evolve the wheel". Though evolution is of course contingent ("random") too.

Feb 06, 2019
So I browsed the paper, which looks good and careful. (Though they omit a discussion of how well their null model power law fits model in comparison with, say, log-normal distributions from evolutionary null-model drift.)

Some finds are that random (bio-)chemistry do not show scaling laws, but biology does from metabolic up to ecological and they can test for that (e.g. life or non-life). In my eyes likely as a result of constrained evolution imprinting the scaling behavior, a hypothesis supported by that they can distinguish through test large clades (Archaea, Bacteria, and archaeal Eukarya).

Feb 07, 2019
I would consider these findings & conclusions as helping to confirm ore-biotic chemistry assembling to biology as a randomly automatic process of indeterminate, unpredictable organization. With a who;e lot of failures.

Out of a dozen or so small, rocky planets in this star system? Only one, the Earth, was able, is able to sustain a biosphere.

So there are natural constraints for originating & maintaining Life.
No need to twiddle your thumbs waiting for a supernatural spooky to make up it;s damn mind which planets will be dealt the marked cards of divine intervention.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more