evolution – Australian Science

Weekly Science Picks

Kelly Burnes — Sun, 10 Mar 2013 00:17:20 +0000

Google celebrated International Women’s Day with a Doodle
Source: Google

Women. This is the theme of this edition of Weekly Science Picks. Yesterday, in case you missed it, was International Women’s Day. And it is important to note the achievements of women in careers such as teaching, neuroscience and engineering because women are still in a tightly contested race with the male counterpart. But who doesn’t enjoy a little competition?

The articles selected this week touch on another issue that is being hotly debated in the U.S. as of late – the question of if women can have it all. Many of you have perhaps heard that Sheryl Sandberg, COO of Facebook, has started down a path of empowering women with her new book released this week, “Lean In: Women, Work, and the Will to Lead”, accompanied by the creation of Lean In Circles, a social networking group to help women express issues of dealing with work and family. I’m not going to get into a debate about this right now, except to encourage some discussion of this topic among our readers, female or male, and think how it applies to life in the sciences.

This first pick deals with exactly this topic. It is a selection of women in science from around the globe, tackling incredible and exciting challenges in the lab, and outside of it with families.

From the frontline: 30 something science, What’s being female got to do with anything, ask the scientists who are starting labs and having kids by Heidi Ledford, Anna Petherick, Alison Abbott & Linda Nordling

“I never thought that my life had to be limited to anything, and I want to set that example for my daughter.

Cite this article:
Burnes K (2013-03-10 00:17:20). Weekly Science Picks. Australian Science. Retrieved: Apr 28, 2024, from http://australianscience.com.au/news/weekly-science-picks-22/
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Ediacara: a “failed” evolutionary experiment?

Kevin Orrman-Rossiter — Tue, 12 Feb 2013 00:11:36 +0000

The Ediacara Hills, north of the city of Adelaide in South Australia are a tumbling mass of ancient rocks. Sunbaked now, 580 million years ago they were a sea alive with soft-bodied organisms. These organisms varied greatly: from millimetres to metres in size; from “blob-like” to intricate in complexity; and from sturdy and resistant to a jelly-soft rigidity. They are all prosaically named the Ediacaran biota. A mundane name for what are the earliest known multicellular organisms on Earth.

Turning over rocks and finding fossils

In 1946, an Australian mining geologist named Reginald Sprigg was inspecting abandoned mines the Ediacara Hills. These hills take their name from the aboriginal Idiyakra, “water is present”. Serendipitously, while eating his lunch, Sprigg found fossilized imprints of soft-bodied organisms on the undersides of slabs of quartzite and sandstone. Most were round, disc-shaped forms that Sprigg dubbed “medusoids” from their seeming similarity to jellyfish. Others, however, resembled worms, arthropods, or even stranger things; quilted mattresses and mud-filled bags.

Reginald Sprigg. Photo credit: Wiki commons.

Sprigg thought that these fossils were ancient and dating from the Cambrian era (541-485 million years ago). He submitted a paper to the journal Nature, but it was refused. Sprigg travelled to London and presented his findings to the 1948 International Geological Congress, but failed to excite either interest or belief.

A time-coil of the Earth’s ages from formation to the present age. Adapted from Press and Siever (2000) Understanding the Earth.

These were not the first Precambrian soft-bodied fossils to be found and described — scattered reports of them had appeared in the scientific literature as far back as the mid-nineteenth century.

The first Ediacaran fossils discovered were the disc-shaped Aspidella terranovica in 1868. Their discoverer, Scottish geological surveyor Alexander Murray, found them to lay below the the Cambrian strata that were then thought to contain the very first signs of life. It took a further four years for anybody to dare propose they could be fossils. Elkanah Billings‘ 1872 proposal was dismissed by his peers on account of their simple form. They were instead declared gas escape structures, inorganic concretions, or even tricks played by a malicious God to promote unbelief.

Aspidella. Image source Wikipedia.

This one-sided debate soon fell into obscurity as no similar structures elsewhere in the world were then known. In 1933, Georg Gürich discovered specimens in Namibia. They were assigned to the Cambrian Period by the firm belief that life originated in the Cambrian, and no link to Aspidella was made.

It was not until the 1957 British discovery of the frond-shaped fossil Charnia in England’s Charnwood Forest that the pre-Cambrian was seriously considered as containing life. Due to the detailed geological mapping of the British Geological Survey there was no doubt that these fossils sat in Precambrian rocks.

The iconic Ediacaran Charnia. Image source Wikipedia.

University of Adelaide palæontologist Martin Glaessner finally, in 1959, made the connection between this and the earlier finds. With a combination of improved dating of existing specimens and an injection of vigour into the search many more fossils were recognised.

The naming the “Ediacaran” period

Due to this punctuated discovery a plethora of different names existed for this pre-Cambrian period and its biota. In 1960 the French name “Ediacarien” was added to the competing terms “Sinian” and “Vendian” for late-Precambrian rocks, and these names were also applied to the life-forms. “Ediacaran” and “Ediacarian” were subsequently applied to the epoch or period of geological time and its corresponding rocks. In March 2004, the International Union of Geological Sciences ended the inconsistency by formally naming the terminal period of the Neoproterozoic after the Australian locality.

The rise of the soft-bodied Ediacaran

It took almost 4 billion years from the formation of the Earth for the Ediacaran organisms to first appear, 655 million years ago. Fossils of single-cell organisms are reported from an age 3,460 million years ago. The first uncontroversial evidence for life though is found 2,700 million years ago. Cells with nuclei certainly existed by 1,200 million years ago.

The reason why it took so long for forms with an Ediacaran grade of organisation to appear is uncertain. A primary size-limiting factor is the amount of atmospheric oxygen. With the low oxygen levels in the early Earth, as low as 0.1% of today’s levels, organisms had to be simple. The oxygen cannot reach the centre of a complex organism quickly enough to supply its metabolic demand. So without sufficient oxygen life could only be very simple.

On the early Earth, reactive elements such as iron and uranium existed in a reduced form, which would react with any free oxygen produced by photosynthesising organisms. Oxygen would not be able to build up in the atmosphere until all the iron had rusted and other reactive elements had also been oxidised.

Banded ironstone, sedimentary oxidised iron. Image source Wikipedia.

Periods of intense cold have also been suggested as a barrier to the evolution of multicellular life. The period preceeding the Ediacaran is known as the Cryogenian. The greatest ice ages known to have occurred on Earth, possibly covering the entire planet, occurred during this period. These ‘snowball earth‘ events are still the subject of much scientific controversy, whether these glaciations were truly global or merely localised events. The diversity of life in modern Antarctica has also sparked disagreement over whether cold temperatures increase or decrease the rate of evolution.

Antarctica snow dome. Image source Wikipedia.

Oxygen, is still seen as key to enable cells to cluster and differentiate. It seems to have accumulated in two pulses; the rise of small, sessile (stationary) organisms seems to correlate with an early oxygenation event, with larger and mobile organisms appearing around the second pulse of oxygenation – the rise of the Endiacaran.

Life, but not exactly as we know it

The advantages of multicellularity include increased size and specialisation, physical protection and conditions for the development of complex behaviour. Unfortunately the soft-bodied physiology of the organisms have meant that fossil remains make their nature speculative and seem quite alien.

Microdictyon, fossil and artists impression. Image source Wikipedia.

While some can be likened to modern jellyfish, corals and lichens, many others remain more enigmatic. For example the Charnia are lacking any mouth, gut, reproductive organs, or indeed any evidence of internal anatomy, their lifestyle was somewhat peculiar by modern standards; the most widely accepted hypothesis holds that they sucked nutrients out of the surrounding seawater by osmosis.

The demise of the Ediacaran

The Cambrian period is marked by the appearance of organisms who evolved the ability to precipitate minerals used for skeletons and hard shells. Organisms which are more easily preserved as fossils than soft-bodied ones. This “Cambrian Explosion

Cite this article:
Orrman-Rossiter K (2013-02-12 00:11:36). Ediacara: a "failed" evolutionary experiment?. Australian Science. Retrieved: Apr 28, 2024, from http://australianscience.com.au/science-2/ediacara-a-failed-evolutionary-experiment/

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Weekly Science Picks

Magdeline.L — Sun, 25 Nov 2012 00:15:18 +0000

The midlife crisis is more complicated than first thought. It might be time to stop blaming troubled marriages and feeling obsolete in a sea of younger colleagues. A study published in the Proceedings of the Natural Academy of Sciences has revealed that chimpanzees and orangutans also experience a midlife crisis.

Having a midlife crisis may not just be the result of a troubled marriage or the thought that life may be halfway over. It might be part of primate biology. That’s right, hardwired into us.

Economist Andrew Oswald told ABC Science that it might be beneficial.

“Maybe discontent lights a fire under people, causing them to achieve more for themselves and their family.”

A shiny new red sports car might just indeed lead to better things.

Danielle Spencer runs a science club at Mitchelton State School in Queensland and explored where gender stereotypes in science began. Where does the perception that men do the “hard” sciences and women do the “soft” sciences come from? A group of 45 primary school students were surveyed and it was found that a majority of students thought that science was accessible to both genders.

When asked why there are more men than women in engineering roles, the students responded with gender based answers like “Girls like dancing and other jobs.” and “Women are more suited to caring and developing jobs like childcare and nursing.”. There was no response that challenging this observation. This was despite 75% of the group thinking that science was accessible to them. It is disheartening to hear.

Students were asked whether their science club should be split into a boys only and girls only science club, there was overwhelming support for a combined science club. There was an appreciation and acknowledgement that irrespective of gender, everyone had a valuable contribution. At the moment this cohort of students believe that science is something that everyone can do. The question remains though, how do we get adults to believe this?

As this week drew to a close, attention focused on NASA’s Jet Propulsion Laboratory in Pasadena, California. A story broke at NPR reporting that the Curiosity Rover may have found some exciting news. Project Scientist at the Mars Science Laboratory, John Grotzinger was quoted to saying:

“We’re getting data from SAM as we sit here and speak, and the data looks really interesting.”

SAM, the Sample Analysis at Mars is a miniaturised chemistry lab. On board is a Gas Chromatograph, Quadrupole Mass Spectrometer, Tunable Laser Spectrometer as well as sample processing systems that allow heating and chemically treating samples. Normally these instruments would fill the space in a laboratory but on Curiosity it’s around the size of a microwave. SAM is being used to collect information about the past and present chemistry of Mars. As well as this SAM is also identifying organic and inorganic chemical molecules known to be important to life on Earth.

So what has SAM found? Nothing has been confirmed but it does sound like there is something especially when Grotzinger says:

“This data is gonna be one for the history books.”

We will have to wait at least several weeks before NASA makes an announcement.

New Zealand’s volcano, Mount Tongariro made it into this week’s news with an eruption on Wednesday. Luckily there have been no reports of damage or injuries. However, a group of travellers and journalists hiking at the time witnessed and filmed the eruption.

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The clues to human uniqueness

Charles Ebikeme — Mon, 02 Jul 2012 00:52:17 +0000

Over 2 million years ago, before the emergence of the genus Homo, within the rift valleys and savannah grasslands of Africa during the Pliocene period, a unique event took place. One that, with some hyperbole, admittedly, shaped the course of human evolution. The event was on a molecular scale but had its bearings on what we now call and search for as the “human condition

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