Ediacarans: the mysterious first complex life on Earth

[Brian G Turner]

I just find it fascinating that we still have no idea whether the first complex creatures to evolve on Earth were animals or plants, so I thought I'd start a thread about them.

Here's one from earlier this year when scientists tried to make a 3D scan of a fossilized ediacarian:
See inside the 580-million-year-old creature no one understands

And a more recent article, where one or more ediacarian species may have survived another 200 million years: Odd fossils hint first complex life hung on long after its time

 

[Foxbat]

Here's an article about the possible first form of life on Earth.
What Was the First Life on Earth?

Personally, when it comes to complex life, I'd have thought that plants would precede animals. My reasoning being that Oxygen would be almost non-existant because of its tendancy to react with many other elements until life capable of photosynthesis evolved and produced it in abundance.

 

[Vertigo]

Here's an article about the possible first form of life on Earth.
What Was the First Life on Earth?

Personally, when it comes to complex life, I'd have thought that plants would precede animals. My reasoning being that Oxygen would be almost non-existant because of its tendancy to react with many other elements until life capable of photosynthesis evolved and produced it in abundance.

Isn't that exactly what the bacteria did and were doing long before the first plants appeared?

The answer is tiny organisms known as cyanobacteria, or blue-green algae. These microbes conduct photosynthesis: using sunshine, water and carbon dioxide to produce carbohydrates and, yes, oxygen. In fact, all the plants on Earth incorporate symbiotic cyanobacteria (known as chloroplasts) to do their photosynthesis for them down to this day.

(From Scientific American)

 

[Venusian Broon]

These fossils (okay, burrows and tracks) of worm-like creatures puts complex animal life at that period as (okay give or take 40 million years ):

Newly discovered fossils reveal earliest complex life on Earth

It seems that the main driver of oxygenation was cyanobacteria - I believe a great many fossilised bacterial mats have been found - and I think I agree , Foxbat, that Oxygen must have been an element that helped caused complex life to develop. But conditions for large plants, i.e. in a place close to light, might have taken a long time to become benign. The hothouse earth of anaerobic times was very harsh. Whereas I can imagine, living as a tiny worm in a bit of mud at the bottom of a pond had more protection?

So I'm not so sure I could call it complex plant or animal first!

 

[Brian G Turner]

I just find it amazing that we can't even classify ediacarians - they just don't resemble anything we're familiar with.

I love a good science mystery.

 

[Vertigo]

To be honest I'm ashamed to say that I'm not absolutely certain what the technical difference is between flora and fauna!

 

[Venusian Broon]

To be honest I'm ashamed to say that I'm not absolutely certain what the technical difference is between flora and fauna!

I'd say ability to photosynthesis is probably a reasonably big factor

(And before you point it out, Fungi - who don't photosynthesis - are no longer in the Vegetable/Plant kingdom, but have a Kingdom all their own now )

 

[Vertigo]

Yeah but bacteria do

 

[Ursa major]

I'm not absolutely certain what the technical difference is between flora and fauna

Flora comes in tubs and is the colour of butter; fauna are, as their name suggests, more of a yellowish tan colour and tend to be obsequious....

 

[Venusian Broon]

Yeah but bacteria do

Only some do, and Bacteria ain't animals or plants either and get their own kingdom - a bit like Fungi.

Also much easier to spot on the cellular level as all bacteria don't have nuclei and other fancy organelles within their bodies. So that's probably a good split.

 

[Vertigo]

Okay, after a bit of googling this seems like a good definition of animal:

[an animal is] any living organism characterized by voluntary movement, the possession of cells with noncellulose cell walls and specialized sense organs enabling rapid response to stimuli, and the ingestion of complex organic substances such as plants and other animals

 

[mosaix]

Yes, I seem to remember being taught voluntary movement was the main thing.

 

[Vertigo]

Yes, I seem to remember being taught voluntary movement was the main thing.

And that doesn't necessarily mean always wandering around the place like, for example, a coral polyp. I also saw another description that mentioned that plants make their own food whilst animals do not. However that distinction doesn't seem to allow for carnivorous plants like the Venus Fly Trap.

 

[Foxbat]

I'm not sure that the Venus Flytrap workings would be classed as voluntary movement. Yes, it's got built in safeguards so that it detects the difference between, say, a raindrop and an insect. Two hairs must be triggered within twenty seconds of each other before the plant will react and another five hairs have to be stimulated when the trap is shut (this would be created by a struggling insect) before it secretes its digestive juices. All of this is to conserve energy but none of this, however, would need to be voluntary (more like a bilogical AND Gate).

 

[Vertigo]

I'm not sure that the Venus Flytrap workings would be classed as voluntary movement. Yes, it's got built in safeguards so that it detects the difference between, say, a raindrop and an insect. Two hairs must be triggered within twenty seconds of each other before the plant will react and another five hairs have to be stimulated when the trap is shut (this would be created by a struggling insect) before it secretes its digestive juices. All of this is to conserve energy but none of this, however, would need to be voluntary (more like a bilogical AND Gate).

Oh I agree completely; I was referring to the alternative description that plants make their own food whilst animals do not ie. animals eat other creatures or plants whereas plants synthesise their food using the sun (typically) for energy.

 

[Foxbat]

Oh I agree completely; I was referring to the alternative description that plants make their own food whilst animals do not ie. animals eat other creatures or plants whereas plants synthesise their food using the sun (typically) for energy.

Ah. My bad