if dinosaurs were reptiles and cold blooded, what would cause the evolutionary step to become warm blooded and birds as it’s said that birds are the closest living relatives of dinosaurs.
In: Biology
As a species evolves over time, genetic mutations that are more “beneficial” will lead to a longer lifespan and more chances to breed. The simplest answer is that when you have a dinosaur with a genetic mutation that gives it warm blood and wings, it allows for a better chance of survival and more opportunities to breed, making those traits more common over countless generations.
As for what CAUSES genetic mutations, there’s no real underlying cause. Random mutations will just occur over time and those that benefit the survival of the species will be selectively chosen over those that make survival more difficult. Same reason why arctic animals have a lot of fur and blubber, it helps them survive freezing temperatures year-round.
Edit: also as others have pointed out already, most dinosaurs were, in fact, believed to be warm blooded to begin with
Some dinosaurs were warm-blooded, possibly the direct ancestors of the birds to be specific.
In fact, there is still a warm-blooded lizard alive today. The Argentinian Tegu is partially endothermic.
In addition to what’s been said, you may have noticed that only birds and mammals among extant animals have fibrous insulation. This only makes sense: if you’re warm blooded you need insulation, whereas if you’re not, you want to be able to expose your body to the sun to warm it up.
Feathers that were not aerodynamic evolved among dinosaurs before flight. In fact, most or maybe all therapods had something akin to feathers at some point in their lives, and seems likely that its primary purpose was insulation.
Larger dinosaurs, it should be added, were basically beyond needing to worry about it one way or the other. Once you reach a certain size, you are basically warm blooded by default because your mass is so much more than your surface area.
Many dinosaurs (and all birds) are thought to have been warm blooded. From the wikipedia article on dinosaurs, “Birds belong to the dinosaur subgroup [Maniraptora](https://en.wikipedia.org/wiki/Maniraptora), which are [coelurosaurs](https://en.wikipedia.org/wiki/Coelurosauria), which are theropods, which are saurischians.”. There are several existing branches of reptiles of which one gave rise to the dinosaurs and birds and another gave rise to the mammals. Warm-bloodedness arose several times throughout the history of life. In additions to (many) dinosaurs, birds, and mammals, many sea reptiles are thought to have been warm-blooded ([ichthyosaurs](https://en.wikipedia.org/wiki/Ichthyosaur), [pterosaurs](https://en.wikipedia.org/wiki/Pterosaur), [plesiosaurs](https://en.wikipedia.org/wiki/Plesiosaur)). See https://en.wikipedia.org/wiki/Dinosaur_renaissance. Also see [https://en.wikipedia.org/wiki/Mammaliamorpha](https://en.wikipedia.org/wiki/Mammaliamorpha) and [https://en.wikipedia.org/wiki/Evolution_of_mammals](https://en.wikipedia.org/wiki/Evolution_of_mammals) for the mammal lineage.
Birds are not the closest living relatives of dinosaurs. Birds are dinosaurs. Birds are the only dinosaurs alive.
The closest living relatives to dinosaurs that aren’t dinosaurs are crocodilians.
First off, dinosaurs aren’t reptiles per say, and a good bit of evidence points to them not being cold blooded often. It’s not always a binary option either, a mesotherm is between warm and cold blooded, and if I recall correctly, a good number of dinosaurs were thought to be this.
And, this not being a binary option, you can better imagine this being a stepwise adaptative process according to your environment. There’s pros and cons to each, with warm blooded often allowing you to be much more active (and survive colder climates), but much less energy efficient (and thus requiring more intake).
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