First living things on land clarification
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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)
- In the video on the Cambrian explosion
- I talked about how suprisingly, or somewhat surprisingly
- animals were the first to colonize
- or to move on land.
- They did that before plants did.
- And someone brought up a question which I thought was a very good question.
- If they were the first, what did they eat?
- I thought it was a good question
- and it justified a 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 here.
- So this 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 eukaryotic
- 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 coastal rocks
- about 1.2 billion years ago.
- G for "Giga".
- 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.
- Now in the last video where I talk about animals
- colonizing the land first
- they weren't animals that only existed on land.
- They were animals that probably spent
- most of their time in the ocean collecting food or whatever
- and they would show up on land 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 spider-like creatures
- but it still would have been at the coast.
- And these would have been creatures that spent a lot of time
- in the ocean
- and some time on land.
- So this is what I was referring to
- as kind of animals colonizing 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 live part of their lives
- on land, you'd get the animals
- things that live their whole life on land, then you'd get 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 of the plants themselves
- we have fossils of their spores.
- But we think that these, the earliest fossils of their spores, that shows that these existed
- were about 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
- 475 million years ago we have evidence
- of what we would call "really" plants
- but the evidence is really the fossils of their spores.
- And then the first evidence of what you could call
- real 'animals' that have spent their entire life on the land
- the oldest fossil we have was discovered in Scotland fairly recently in 2004
- and it was...
- this is the fossil over here, it was discovered by a bus rider, Mike Newman
- it was a bus driver in Scotland, and they actually named the thing after him.
- It is called Newmati,they got the Numati from Mike Newman
- and this fossil is 428 million years old
- 428 million old
- and right now it is the oldest fossil we have of a true land animals
- if we think about true land animals
- if you think about true plant versus true land animals that spend their entire life on the land
- if you think about about things that spend part of their time on the land, then the animals probably would
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