Dinosaurs & Birds

[khallam]

Hello,

I am easily confused! haha But recently I have been re-watching WWD and listening to some Dino audio books/podcasts and time and time again come the line Dinosaurs are all around us - the birds.

I am not saying I doubt this by any means. Where I get confused (and like I said easily done!) is birds were already well established during the time of the Dinosaurs, so how can one species evolve into a species that was already 'in play'

Thanks 

[stargatedalek]

"Dinosaurs" are not "a species", they are a massive broad group that includes many, many different smaller groups of animals. One of the largest of these groups within dinosaurs is birds.

Additionally, that isn't ho evolution works. A single instance of evolution affects a single breeding population of a species, not an entire species at the same time.

[CityRaptor]

Exactly.
Within Dinosauria, there is Theropoda, and within Theropoda, there is Aves ( birds ).

Compare Synapsida.. Within Synapsida there is Mammalia and the largest group within Mammalia are the rodents. 

[khallam]

"Dinosaurs" are not "a species", they are a massive broad group that includes many, many different smaller groups of animals. One of the largest of these groups within dinosaurs is birds.

Additionally, that isn't ho evolution works. A single instance of evolution affects a single breeding population of a species, not an entire species at the same time.

Thanks for clearing that up

[khallam]

Exactly.
Within Dinosauria, there is Theropoda, and within Theropoda, there is Aves ( birds ).

Compare Synapsida.. Within Synapsida there is Mammalia and the largest group within Mammalia are the rodents.

Thanks

[Halichoeres]

I have a PhD in Evolutionary Biology, so you should always feel free to ask me questions about how evolution works. I think CityRaptor and stargatedalek made some good points, but I want to elaborate just a little. It's really easy to think of evolution as a linear process where a given lineage just keeps progressing and improving, but it's really more of a tangled bush. Lineages are constantly originating, and most of them are dead ends. A few becomes really successful. So, among dinosaurs, that includes a whole mess of theropod groups, a few sauropod groups, and several ornithischian groups that were all quite diverse during the Late Cretaceous (each containing several to many species). When an extinction event happens (like the end of the Cretaceous), lots of branches might get pruned, so to speak. It's just that a handful of the branches, composed of the smallest, fluffiest dinosaurs, were the only ones that didn't get pruned. Those survivors diversified into the modern birds, around 10,000 species.

Relatedly, it seems like you wonder how something can coexist with something that is ancestral to it. Generally speaking, it doesn't. So you'll sometimes hear people wonder ask things like "if humans came from apes, why are there still apes?" No biologist claims we came from a living species of ape. Rather, we share a common ancestor with living apes. If we could go back in time and find that ancestor, we would probably refer to it as ape-like--it doesn't mean we're coexisting with our ancestor, however. In the same way, modern birds are of course quite dissimilar to their ancestors and dead-end great-great.........-great-uncles that lived with the non-bird dinosaurs.

[Dinoguy2]

Here's a simple way to think about it: There were lots of dinosaur groups that flourished during the Mesozoic. Sauropods, cerstopsians, hadrosaurs, therizinosaurs, tyrannosaurs, birds, dromaeosaurids, ankylosaurs, etc. Only one of these groups survived the extinction.

[Gwangi]

Here's a simple way to think about it: There were lots of dinosaur groups that flourished during the Mesozoic. Sauropods, cerstopsians, hadrosaurs, therizinosaurs, tyrannosaurs, birds, dromaeosaurids, ankylosaurs, etc. Only one of these groups survived the extinction.

I like to use the analogy that if all mammals died out except for bats that the bats would still be mammals.

[Libraraptor]

Here's a simple way to think about it: There were lots of dinosaur groups that flourished during the Mesozoic. Sauropods, cerstopsians, hadrosaurs, therizinosaurs, tyrannosaurs, birds, dromaeosaurids, ankylosaurs, etc. Only one of these groups survived the extinction.

I like to use the analogy that if all mammals died out except for bats that the bats would still be mammals.

Best explaination ever.

[Halichoeres]

The bat analogy really is a good one.

[CityRaptor]

Basically New Zealand before the arrival of humans. ( Ignoring Marine Mammals here )