Why did birds evolve to be much smaller than dinosaurs? What natural selection feature drove this drastic change in size? 🦖🕊️ #BirdEvolution #DinoAncestors #NaturalSelection
The Evolutionary Puzzle: Birds vs. Dinosaurs
– Dinosaurs were massive creatures that roamed the earth millions of years ago. But how did their avian descendants end up so tiny in comparison?
– What role did natural selection play in shaping the size of birds over time?
The Key Factors Driving Bird Size Evolution
1. **Adaptation to Flight**: As birds took to the skies, being smaller and lighter became advantageous for enhanced maneuverability and efficiency in flight.
2. **Environmental Pressures**: Changes in habitat and available food sources may have favored smaller birds that could adapt more easily to varied conditions.
3. **Predation**: Smaller size could have been an advantage in escaping predators or hunting for food in diverse ecosystems.
Let’s unravel the mystery behind the size difference between birds and their dinosaur ancestors! 🤔🌍 #EvolutionMystery #DinoBirds #SizeMatters
It’s definitely no “if” at this point, since the evidence is overwhelming. As for selection pressure, they already started out as fairly small dinosaurs to begin with given how the largest ones struggled the most during the extinction, but there are likely advantages to remaining fairly small as a bird given how it makes it easier to fly.
I think that question is in reverse. It’s not that there was a pressure that caused birds to develope to a different size from other species with the same common ancestor,
it’s that those species, who developed from the same common ancestor as dinosaurs, and were smaller, managed to survive to today and became known as birds.
Though if you’re asking why most (if not all) of the ‘larger’ species went extinct, it’s exactly because extinction events are worse for highly specialized species, as they are more prone to disruptions in their food chains (which extinction events generally cause). Large size is a specialization, and in particular one that requires a larger availability of food to sustain a stable populace.
Birds didn’t evolve from dinosaurs, they are dinosaurs. Some have evolved to be quite large flightless birds, some are semi aquatic. It happens that post mass extinction mammals have filled many of the ecological niches that dinosaurs used to occupy due to some evolutionary advantage over birds.
The dinosaur lines that ended in birds were already small. Think less T-Rex more housecat.
Dinosaurs were a huge family, like mammals. The big ones are famous but keep in mind mammals cover a range from smaller than a mouse up to the blue whale.
Small size in and of itself was critical to developing gliding and eventually flying. We’ve never seen evidence in the fossil record of something big starting to fly. They start small, where gravity is easier to fight, and then after the mechanics of flight are refined they grow.
Beyond that, extinction events tend to hit larger creatures the worst. They just need too many resources and predators even more so because they need the cumulative result of all the resources many large herbivores consumed.
To answer this, first we must answer what is natural selection. Animal linages diverge slowly over time, selecting the advantageous mutations by reproductive success. That means two animals, even closely related, could have very different eating and mating strategies. Over time and generations, those small mutations continue to mutate into animal specific traits. Some of which we can see in today’s living animals.
There was also the climate and environmental factors to consider too. Back 65 million years ago the Earth was much warmer and had more oxygen in the air. This helped lend to the larger body size of dinosaurs.
The last major extinction event was the meteor impact, which killed all the non avian dinosaurs, and freed the path for mammals. Now most creatures who survived that impact event were small. This is due to smaller animals needing less food to survive. They also tended to live in places where selective pressure kept them relatively small.
Today’s birds are small because of natural selection. There are less large predators, so being large doesn’t have the advantages of less predators, and you need more food. There is less oxygen in the air, which also tends to smaller body sizes.
TL:DR Bird’s have always been small, after the KPG extinction event the selective pressures were no longer there for large bodied birds.
The atmosphere had more nitrogen back in the time of the dinosaurs. More oxygen and warmer also. So there was a different size limit then compared to now. Back then there were 6ft dragonflies big enough to drag a small person off.. so.. yea.. thank god they’re smaller now 😂 imagine a 14ft pelican just eating people off the beaches
Birds evolved from a group of dinosaurs known as theropods, which included species like Velociraptors and Tyrannosaurus rex. Over time, natural selection favored smaller body sizes in some theropods, leading to the emergence of birds.
The current conversation isn’t whether birds evolved from dinosaurs, but whether they are a type of dinosaur.
[https://www.birdlife.org/news/2021/12/21/its-official-birds-are-literally-dinosaurs-heres-how-we-know/](https://www.birdlife.org/news/2021/12/21/its-official-birds-are-literally-dinosaurs-heres-how-we-know/)
As to size – it’s the same concept as house cats evolving from wild cats but being much smaller than lions -they evolved from a line of small wild cats.
Bird’s lineage is from a small line of dinosaurs. It is more difficult for larger animals to survive in general, so after the asteroid situation the big dinosaurs struggled and died out while the smaller dinosaurs / birds were able to survive.
Everything over a certain size died during an extinction event, terminating those lines. The survivors of the KT Extinction were the smallest lifeforms around, as they required the least amount of energy to survive.