Cosmology and astronomy
First living things on land clarification
First living things on land clarification (This video copyrighted under Create Commons Attribution and Share-Alike CC-BY-SA license). Created by Sal Khan.
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- Sorry if this is unrelated directly to this topic, but prehistoric creatures like the dinosaurs lived about 200 million years ago. If we were able to take enough advanced technology to a planet 200 million light years away and look at the Earth, would we see the dinosaurs?(19 votes)
- Assuming we can travel much faster than the speed of light to a planet 200 million light years away, we would be able to see earth as it looked 200 million years ago if we went and built a telescope at that distance since it would have taken light 200 million years to travel such a distance. Of course, you would also need an incredibly powerful telescope if you wanted to see earth and not just our sun. Currently, we can't directly see earth-sized planets orbiting other stars due to glare from their parent star and their comparatively small size. Now for the matter of actually, "seeing" dinosaurs, you would need a telescope far far beyond anything currently imaginable.(44 votes)
- was there dirt back when the first plants were on earth?(14 votes)
- No there was not that much dirt we have these day's. The first life on land actually where fungi and then mosses (plants). Fungi came about 542–488.3Ma and made the rocks crack so that early mosses could stay in place with roots. Fungi where first because they need, just like mosses, a wet environment. Plants can't live on hard rock. Even today, on rocks, the mosses are the first to survive and prepare the area for other plants by making cracks wider and so on. Also because of the atmosphere there is weather (think about wind and other erosion effects). In this way, together with fungi, plants could evolve from the earliest forms to the gigantic trees we know these days!(17 votes)
- At3:00sal says that we only have fossils of spores not plants. Why is that?(8 votes)
- Spores have something inside them that can't be decomposed and can be turned to rock when compressed by layers and layers of dirt (that's how a fossil forms). But plants are made mostly of tissues, and everything is degradable. Plants can be preserved though, with the help of amber.(12 votes)
- How did the first plants come to existence?(7 votes)
- When single celled organisms (like bacteria) formed, then became plankton they came together, then grew intelligence,changed DNA and came on land and that became algae then the plants we see today formed and then trees!(6 votes)
- How was the age of the oldest fossil determined to be 428M years old?(4 votes)
- Carbon Dating is only good for objects that are < 50,000 years old. After that, there is no carbon left to date. For objects that old, you would need to use some type of radiometric dating.
- Does the A in Ma stands for Annos? Maybe silly question i think it makes sense but im not sure.(3 votes)
- I'm not sure, but I think "Ma" means "Mega Ago". If that makes sense.(1 vote)
- I've realized, there were no soil on the earth, only rocks, boulders and the like. Were the first plants without roots? Other words, what was a way of their feeding?(4 votes)
- Algae is technically neither plant nor animal. Also water turns rock into sand over hundreds of years. When plants or animals die, they turn into dust. And sand or dust, well they are basically a form of dirt.(3 votes)
- What is the first living thing to go deep inland? Plants? Or Animals?(3 votes)
- Probably plants.
Without a viable food source, animals most likely were not able to extent beyond the coastlines and other nearby bodies of water.(3 votes)
- How did the plants reach the land since they can't walk?(2 votes)
- Seeds/plants were probably washed onto the shore.(3 votes)
- did plants change their looks to become like what we call a plant?(3 votes)
- They evolved over millions of years to accommodate their environment and slowly became what they are today.(3 votes)
In the video on the Cambrian explosion, I talk about how surprisingly, or somewhat surprisingly, that animals were the first to colonize or to move on land. They did that before plants did. And someone brought up what I thought was a very good question. If the animals were the first, what did they eat? So I thought that was one, a good question. So it justified a whole video on clarifying exactly who was first on the land. So right here, this is a picture of algae on the coast. This is kind of algal scum right over here. So this right here is algae. And just to be clear, sometimes cyanobacteria, which we talked about as the first photosynthetic organism, sometimes that's called blue-green algae. But that's really bacteria. Algae is considered to be eukaryotic. And it just doesn't have the structures of modern plants. So this is algae right here. And our best estimate is that algae actually colonized kind of coastal rocks about 1.2 billion years ago. So this is 1.2 billion years ago, "g" giga, billion years ago. So if you wanted the first thing that even resembled or was close to plants or animals, and if you consider algae close to a plant, then this would be the winner of who got on land first. This is 1.2 billion years ago. Now in the last video where I talk about animals colonizing the land first, they weren't animals that only existed on land. They would have been animals that probably spent most of their time in the ocean collecting food or whatever. And then they would show up on the land maybe to lay eggs. And if you think about it, back then the land would have been a really good place to lay eggs because there wouldn't have been much else on the land. So you would have been protected from predators. So it might have been slug-like creatures like this. Some people talk about kind of spider-like creatures. But it still would have been at the coast. And these would have been creatures that would have spend a lot of time in the ocean and some time in their land. So this is what I was referring to as kind of animals colonizing the land before plants. And this would have happened about 530 million years ago. Now, the first living organisms to fully live on the land, their whole life is on the land, those would be plants. So it depends if you think about things that part of their life, you'd get the animals. Things that lived their whole life on the land, then you go back to the plants. So this right here, this is what we think the first primitive plants would have looked like. And the evidence-- we actually don't have fossils from these plants themselves. We have fossils of their spores. But we think that the earliest fossils of their spores, which show that these existed, were about 475 million years ago. So this is-- let me do this in another color-- this right over here is 475 million years ago. So 1.2 billion years ago, you have the algae. 530 million years ago, we have evidence of things kind of oozing out of the ocean and maybe laying their eggs or something. 475 million years ago, we have evidence of what we would kind of call really plants. But the evidence is really the fossils of their spores. And then the first evidence of real-- I guess you could call them animals that spend their entire life on the land, the oldest fossil we have-- it was discovered in Scotland fairly recently, in 2004. And this is the fossil right over here. It was actually discovered by a bus driver, by Mike Newman. Mike Newman, who is a bus driver in Scotland. And they actually named the thing after him. It's called Pneumodesmus newmani. So they got the newmani from Mike Newman. And this fossil is 428 million years old. And right now, it's the oldest fossil we have of a true land animal. So if you think about true plants versus true land animals, things that spent their entire life on the land, the plants do win out. If you think about things that spent part of their time on the land, then the animals probably won out. If you view algae as plants, then the plants won out. So it depends where you want to draw the line. And this first fossil, this is of a myriapod which just means a lot of legs. Let me write over here, myriapod. You probably know the word "myriad." Myriad means a bunch of things or a huge amount. So myriapod, a huge amount of legs. And you might be familiar with the millipedes and centipedes. Those are myriapods. And so those first primitive myriapods, 428 million years ago. And they would have lived off of plants, and maybe other myriapods, and other slugs, and whatever other animals they might have found. They mind have looked something like that. So hopefully, that gives a little bit of clarification over-- it wasn't like you had dogs sitting on the land and they had nothing to eat. It's kind of a gray area in what you define a plant or an animal and who gets kind of the bragging rights for being the first on the land. And it depends on really what you consider a plant or animal and whether spending part of your life on the land, whether spending part of your life on the land will actually qualify.