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When did Life Colonize the Land?

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  • Written By: Michael Anissimov
  • Edited By: Bronwyn Harris
  • Last Modified Date: 10 November 2016
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The first attempts of life colonizing the land were microbial mats, large flat colonies of photosynthetic microbes, fossilized remnants of which have been dated to 2.6 billion and 2.7 billion years ago. For billions of years, microbes were the only forms of life colonizing the land (and the only life in general). These microbes lived mostly on the coasts of the oceans and streams, and would appear as nothing more than a green slime. It would take many more millions of years for life to colonize the land in earnest.

The first possible tracks on land are dated to 530 million years ago, during the Cambrian period. These trace fossils, known as Protichnites and Climactichnites, appear as a series of faint bumps and long grooves resembling motorcycle tracks, respectively. Both these tracks are thought to have been made by early arthropods, and some of them are quite large for the time — as much as 10 cm (4 in) wide. These tracks may have been left by sea scorpions traveling from one tide pool to another.

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The first widespread terrestrial fossils didn't emerge until about 425 million years ago, during the Silurian period. The first life to colonize the land were mosses and lichens. These were followed by simple vascular plants, such as Cooksonia (mostly from the northern hemisphere) and Baragwanathia (from Australia), which were quickly followed by land fungi, which left fragmentary fossils. These plants started off very short, just a couple of inches tall, but left large "forests" of fossils. They did not yet have differentiated stems or leaves.

When the land started to build up a nice layer of soil, more plants could grow, causing a positive feedback cycle of land colonization. By the end of the Silurian period, a simple terrestrial ecosystem had emerged, including millipede herbivores, centipede and arachnid carnivores, worm detritivores, and fungal decomposers. Nematodes were also likely present but have not left fossils. It took several tens of millions of years for life to colonize the land further.

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anon983763
Post 8

Any religion that asks for blind faith is not for me. G-d created our sense of wonder and scientific abilities to help us better understand creation. Groups ask for blind faith when they really want us to bury our heads in the sand and send money. I think scientific method and belief in a higher power are not exclusive until an organization is asking me to believe them without question. G-d didn't give us intellect to not use it and don't ask me to believe intellect is from the devil.

anon150879
Post 6

I think that the reason for this colonizing of the land is complex, however, the main reason for plants is that, at first there was nothing around to eat them. And think the two main reasons for animals is 1) the bounty of plant that flourished because there was nothing to eat them. 2) Because marine predators were growing large and fearsome (i think the shark had recently evolved).

fitness234
Post 5

Biology was the most boring class I ever had throughout my entire education in the public high school system. Maybe it was my lack of interest in science in general, the fact that I didn't like math probably didn't help much either.

Either way, I can understand the basics of how life did colonize land and the movement of organisms from water onto shore. One would think that the drive and motivation to come from the waters and go onto dry land would probably come in the form of meeting more resources. Since life is so basic, I imagine that will most likely happen is that basic organisms that didn't live needed the minerals they could find on trial

and.

When one loosely defines what life is, you run into an issue of asking whether it was animals or plants and the reality is the movement of life onto sure was most likely in the form organisms and plants, moss and algae.

JoseJames
Post 4

I can only imagine what it would've been like to be on the earth when life finally did colonize land. It's hard for our human minds to comprehend the timescale and just how far in the past these events must have occurred.

Because modern science has become exact enough to carbon date specific types of fossils and rocks, we are capable of creating a theory about when colonization windows for life occurred and allowed for the movement of life from water to land.

We have nowhere to go but up words and more knowledgeable and educated about the subjects of microbiology and just how the organisms that invaded our oceans and glance turned into the advanced civilizations that we now have.

thumbtack
Post 3

With the overabundance of evolutionary evidence and massive research having been done in the field of microbiology, biology and evolutionary sciences, there is no doubt in my mind that evolution is what created life that eventually colonized land.

The history of our life timeline is not been completely told nor do I think that it ever will be possible for science to completely fill in UNLESS of course we invent a time machine. Because of this we will never truly know what is because the colonization of land, but what we can do is make educated decisions and estimations about how to approach such a life-changing subject as our creation.

GraniteChief
Post 2

I don't think that evolution ever occurred despite what scientists say today if you believe in God, and you believe creationism. There are no gray areas is a black-and-white line one must accept to pursue his faith.

I suppose if you have the concept of God creating the earth and the heavens in seven days that perhaps it is possible to think about how life could have colonized land afterwords but perhaps it was the matter of a single day.

Either way, this is not the kind of subject that should be taught in school.

anon9317
Post 1

Recent research has provided some additional nuanced information: (1) the tracks are thought to have been made by early arthropods or large slug-like animals, and (2) the tracks may have been left by the organisms (not just sea scorpions) traveling between tide pools or even feeding on organic materials.

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