3 ms·

Yes, sea life blurs the distinction.

by dsq 3y ago

vanderZwan 3y ago
And the distinction gets even messier the further back in time you go. Like, many life-forms among the Ediacaran biota are more closely related to modern animals than to plants, apparently. But for example charnia was a rooted life-form that was a filter feeder. https://en.wikipedia.org/wiki/Ediacaran_biota https://en.wikipedia.org/wiki/Ediacaran_biota https://en.wikipedia.org/wiki/Charnia https://en.wikipedia.org/wiki/Charnia And obviously that distinction should be messy when we go all the way back to the point where the two first started ti separate.
- adrian_b 3y ago
  > And obviously that distinction should be messy when we go all the way back No, the distinction has not been messier in the early times. On the contrary, the distinction was sharp in the beginning and it became messier later. All the so-called eukaryotes, i.e. the living beings with nucleated cells, were animal-like in the beginning (perhaps close to two billion years ago), i.e. they were mobile and they fed by ingesting other living beings. Much later, hundreds of millions of years later, various groups and subgroups of eukaryotes have become sedentary, in some cases because it was more efficient to wait the food to come to them, brought by water currents, than to pursue actively the food, in many other cases because they incorporated phototrophic living beings, e.g. blue-green algae, so they no longer needed organic food, and lastly, many groups have become sedentary after reverting to the mode of feeding of bacteria, i.e. instead of ingesting other living beings, which requires mobility, they went back to absorbing organic substances from the environment through their external surface, which does not require mobility for adults, but only for whatever kind of spores they use for reproduction. This last way of life is characteristic for fungi and for several other groups of living beings which resemble fungi without being related to them. The first sedentary eukaryotes were the multicellular red algae and green algae (some green algae evolved much later to become the land plants), for which certain fossils are about one billion years old. Dubious fossils of red algae are a few hundred million years older. During the early evolution of the multicellular animals, many groups have become sedentary as adults (e.g. the sponges), which in the beginning was somewhat unavoidable for any animals that became large, because a small larva could easily swim using cilia, a small adult could also use cilia, but for a big adult animal cilia are inefficient, so strong muscles are needed to move the body parts, to be able to use those parts for locomotion, and several tens of millions of years have passed until the animals evolved to have such muscles. The start of the Cambrian is defined by the apparition of worms which were strong enough to burrow in the mud from the sea floor.

Yes, sea life blurs the distinction.

by dsq 3y ago

Yes, sea life blurs the distinction.

And the distinction gets even messier the further back in time you go. Like, many life-forms among the Ediacaran biota are more closely related to modern animals than to plants, apparently. But for example charnia was a rooted life-form that was a filter feeder. https://en.wikipedia.org/wiki/Ediacaran_biota https://en.wikipedia.org/wiki/Ediacaran_biota https://en.wikipedia.org/wiki/Charnia https://en.wikipedia.org/wiki/Charnia And obviously that distinction should be messy when we go all the way back to the point where the two first started ti separate.

adrian_b 3y ago
> And obviously that distinction should be messy when we go all the way back No, the distinction has not been messier in the early times. On the contrary, the distinction was sharp in the beginning and it became messier later. All the so-called eukaryotes, i.e. the living beings with nucleated cells, were animal-like in the beginning (perhaps close to two billion years ago), i.e. they were mobile and they fed by ingesting other living beings. Much later, hundreds of millions of years later, various groups and subgroups of eukaryotes have become sedentary, in some cases because it was more efficient to wait the food to come to them, brought by water currents, than to pursue actively the food, in many other cases because they incorporated phototrophic living beings, e.g. blue-green algae, so they no longer needed organic food, and lastly, many groups have become sedentary after reverting to the mode of feeding of bacteria, i.e. instead of ingesting other living beings, which requires mobility, they went back to absorbing organic substances from the environment through their external surface, which does not require mobility for adults, but only for whatever kind of spores they use for reproduction. This last way of life is characteristic for fungi and for several other groups of living beings which resemble fungi without being related to them. The first sedentary eukaryotes were the multicellular red algae and green algae (some green algae evolved much later to become the land plants), for which certain fossils are about one billion years old. Dubious fossils of red algae are a few hundred million years older. During the early evolution of the multicellular animals, many groups have become sedentary as adults (e.g. the sponges), which in the beginning was somewhat unavoidable for any animals that became large, because a small larva could easily swim using cilia, a small adult could also use cilia, but for a big adult animal cilia are inefficient, so strong muscles are needed to move the body parts, to be able to use those parts for locomotion, and several tens of millions of years have passed until the animals evolved to have such muscles. The start of the Cambrian is defined by the apparition of worms which were strong enough to burrow in the mud from the sea floor.