I'm an engineer but this class of interesting Earth sciences will probably help me when brainstorming a new design. I love the brilliant ''engineering solutions'' of life as it evolve.
About the Cambrian explosion, I believe that the reason is mostly genetic. The genome of organism was unstable for some time before mecanism evolved to stabilize the genome. So lots of new organism could evolve when predator arise and higher oxygen concentration in the environment.
Here's a great summary of the recent work on that: www.nature.com/articles/530268a. The point you suggest has also been considered, i.e., did evolution have more flexibility? Given that life was quite old at that point (~3.5 billion years) I find it unlikely that evolution had not worked out how to do DNA repair efficiently, but I am partial to the idea that there was lots of ecological niche space. As oxygen opened up opportunities for animal body plans, basically everything and anything that appeared could be refined into an animal body. From this explosion, came a long winnowing process afterwards with the most successful bodies displacing less efficient and adaptable forms. However, this is an active area of research and an important place for us to be careful, because the rules that apply today may have only been weakly in play and our assumptions about how systems function is built on a world quite different than the one that existed at that time.
There was one planned, but I did not have time to make and upload it. Having said that I am going to uploading more lectures on animal systems in the very near future. Glad you liked the lectures.
So I can't see your pointing, obviously. Is there any chance a student with some editing skills could work with you to add graphics to the video post-facto and upload them? I understood which animal you were talking about as soon as you said "related to velvet worms" and could pick it out in the art (starting around 13:25) but earlier there was simply no reference for me to understandicating. Obviously I appreciate this work being available to me for free, but graphical overlays - especially common overlays like arrows or circles - would help a ton and could be done by almost anyone, so long as you had the time just to make sure that the person is correctly placing the arrows on the right objects (or circling the correct objects, or whatever). Secondly, In the same art there is an animal in the background/right that appears to me somewhat similar to a brittle star. Am I right to think brittles stars and the animal depicted are related? Thanks so much for your work. I'm sure I'll be watching all the videos as time permits.
It's not a primitive trilobite. It is Spriggina. The other flat thing that you've shown is Dickinsonia or another organism in the same family. We are almost certain these are actual animals because we found chemical traces (sterols) that show its not bacteria, fungus or plant. It might be a branch of animals that evolved with simplified or different versions of the body plan genes. Also it's possible they didn't have muscles, although we found traces of an apparent digestive tract in some of these organisms.
Excuse me if my timeline is wrong here but is the Devonian extinction the one where some scientist suggest it may have occurred because of a strong Gamma ray burst, immobile shallow water species unable to survive hard UV.
at 40:13 he talks about coelacanths as if that exhausts the marine sarcopterygians, but that's ridiculous. lungfish are more common than coelacanths, and today there are the whales, dolphins, seals, penguins, sea turtles, and things like that, and together they comprise a significant diversity of marine sarcopterygians. i don't know of a single terrestrial actinopterygian
Lungfish, are of course, fresh water. The other sarcopterygians you mention (the tetrapods) are sarcopterygians but I am trying to discuss a group of fish prior to their emergence onto land. Coelcanths are the last common ancestor of this group in a fully marine setting, prior to the emergence onto land, and reacquiring of a aquatic lifestyle. If you see some of the other lectures I have posted you will note I often talk about the issue of calling things a "fish" when we purposely leave out large numbers of those animals because they walk on land so cannot be fish. Terrestrial, or I would say semiterrestiral actinopterygian, would be any of the mudskipper group. Although numerous actinopterygian use terrestrial or near shore areas outside of the water for breeding.
thanks for the reply. the lungfish point was not exactly right, but then there are lots of actinopterygians in freshwater environments, so that falsifies the point about their being "almost exclusive to the marine environment." the marine tetrapods are marine, so it is still true that there is a significant diversity of marine sarcopterygians, and the rarity of coelacanths is not very relevant to the discussion of the prevalence of sarcopterygii in the oceans. thanks for the mudskipper example. a true statement would be that the actinopterygians are almost exclusive to aquatic (as opposed to marine) environments and that the sarcopterygians are almost exclusive to terrestrial environments, although there are more aquatic sarcopterygians than terrestrial actinopterygians.
Thomas, have you seen this paper? It's about the coelacanth genome, but the analysis shows that lungfish are more closely related to terrestrial tetrapods than they are. www.nature.com/nature/journal/v496/n7445/full/nature12027.html
I'm glad someone pointed this out, it really bothered me while listening to the lecture lol. So thanks! But I must say, that this was an EXCELLENT lecture series to listen to, so thanks to Thomas as well for putting this together (and I do see what your intent was in your reply)! I hope you make more videos/lectures! I'd love one on the topic of the last common ancestor of vertebrates and invertebrates (some kind of tiny, bilateral worm like thing perhaps? I have no idea)
I partly agree. I have noted that I use the word obviously too frequently in conversation. In written conversation I can eliminate it by editing, but I am now focusing on removing it from my lectures as well. Sorry, cannot go back in time to fix that. On the issue of condescension, that requires knowledge about my motives. I can promise you I do not mean to "talk down" to anyone. Knowledge is available for anyone interested and not knowing is not a problem. So in the case of condescension I disagree with you.
I'm an engineer but this class of interesting Earth sciences will probably help me when brainstorming a new design. I love the brilliant ''engineering solutions'' of life as it evolve.
These are very informative lectures. I'm enjoying them 💕
About the Cambrian explosion, I believe that the reason is mostly genetic. The genome of organism was unstable for some time before mecanism evolved to stabilize the genome. So lots of new organism could evolve when predator arise and higher oxygen concentration in the environment.
Here's a great summary of the recent work on that: www.nature.com/articles/530268a. The point you suggest has also been considered, i.e., did evolution have more flexibility? Given that life was quite old at that point (~3.5 billion years) I find it unlikely that evolution had not worked out how to do DNA repair efficiently, but I am partial to the idea that there was lots of ecological niche space. As oxygen opened up opportunities for animal body plans, basically everything and anything that appeared could be refined into an animal body. From this explosion, came a long winnowing process afterwards with the most successful bodies displacing less efficient and adaptable forms. However, this is an active area of research and an important place for us to be careful, because the rules that apply today may have only been weakly in play and our assumptions about how systems function is built on a world quite different than the one that existed at that time.
Hello,
I was wondering if there was a vertebrae history 3? Btw your lectures are amazing!
There was one planned, but I did not have time to make and upload it. Having said that I am going to uploading more lectures on animal systems in the very near future. Glad you liked the lectures.
So I can't see your pointing, obviously. Is there any chance a student with some editing skills could work with you to add graphics to the video post-facto and upload them? I understood which animal you were talking about as soon as you said "related to velvet worms" and could pick it out in the art (starting around 13:25) but earlier there was simply no reference for me to understandicating. Obviously I appreciate this work being available to me for free, but graphical overlays - especially common overlays like arrows or circles - would help a ton and could be done by almost anyone, so long as you had the time just to make sure that the person is correctly placing the arrows on the right objects (or circling the correct objects, or whatever).
Secondly, In the same art there is an animal in the background/right that appears to me somewhat similar to a brittle star. Am I right to think brittles stars and the animal depicted are related?
Thanks so much for your work. I'm sure I'll be watching all the videos as time permits.
It's not a primitive trilobite. It is Spriggina.
The other flat thing that you've shown is Dickinsonia or another organism in the same family. We are almost certain these are actual animals because we found chemical traces (sterols) that show its not bacteria, fungus or plant. It might be a branch of animals that evolved with simplified or different versions of the body plan genes. Also it's possible they didn't have muscles, although we found traces of an apparent digestive tract in some of these organisms.
Excuse me if my timeline is wrong here but is the Devonian extinction the one where some scientist suggest it may have occurred because of a strong Gamma ray burst, immobile shallow water species unable to survive hard UV.
Anomalocaris is not really related to brine shrimps. It is a cousin of velvet worms.
at 40:13 he talks about coelacanths as if that exhausts the marine sarcopterygians, but that's ridiculous. lungfish are more common than coelacanths, and today there are the whales, dolphins, seals, penguins, sea turtles, and things like that, and together they comprise a significant diversity of marine sarcopterygians. i don't know of a single terrestrial actinopterygian
Lungfish, are of course, fresh water. The other sarcopterygians you mention (the tetrapods) are sarcopterygians but I am trying to discuss a group of fish prior to their emergence onto land. Coelcanths are the last common ancestor of this group in a fully marine setting, prior to the emergence onto land, and reacquiring of a aquatic lifestyle. If you see some of the other lectures I have posted you will note I often talk about the issue of calling things a "fish" when we purposely leave out large numbers of those animals because they walk on land so cannot be fish.
Terrestrial, or I would say semiterrestiral actinopterygian, would be any of the mudskipper group. Although numerous actinopterygian use terrestrial or near shore areas outside of the water for breeding.
thanks for the reply. the lungfish point was not exactly right, but then there are lots of actinopterygians in freshwater environments, so that falsifies the point about their being "almost exclusive to the marine environment." the marine tetrapods are marine, so it is still true that there is a significant diversity of marine sarcopterygians, and the rarity of coelacanths is not very relevant to the discussion of the prevalence of sarcopterygii in the oceans. thanks for the mudskipper example.
a true statement would be that the actinopterygians are almost exclusive to aquatic (as opposed to marine) environments and that the sarcopterygians are almost exclusive to terrestrial environments, although there are more aquatic sarcopterygians than terrestrial actinopterygians.
Thomas, have you seen this paper? It's about the coelacanth genome, but the analysis shows that lungfish are more closely related to terrestrial tetrapods than they are.
www.nature.com/nature/journal/v496/n7445/full/nature12027.html
I'm glad someone pointed this out, it really bothered me while listening to the lecture lol. So thanks!
But I must say, that this was an EXCELLENT lecture series to listen to, so thanks to Thomas as well for putting this together (and I do see what your intent was in your reply)!
I hope you make more videos/lectures! I'd love one on the topic of the last common ancestor of vertebrates and invertebrates (some kind of tiny, bilateral worm like thing perhaps? I have no idea)
Wastes time belaboring the obvious. His sentences and phrases which begin with the word "obviously," are condescendingly unnecessary.
I partly agree. I have noted that I use the word obviously too frequently in conversation. In written conversation I can eliminate it by editing, but I am now focusing on removing it from my lectures as well. Sorry, cannot go back in time to fix that.
On the issue of condescension, that requires knowledge about my motives. I can promise you I do not mean to "talk down" to anyone. Knowledge is available for anyone interested and not knowing is not a problem. So in the case of condescension I disagree with you.
Could just be a verbal tic and not intended to be condescending in any way.
@@thomasevans3387 Don't feed online trolls too much Thomas. haha
This was an EXCELLENT series, thank you!
@@thomasevans3387 Don't take the trolls seriously.