how did birds become warm blooded

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Given that dinosaurs were reptiles with cold blood, how did birds become warm-blooded if they derived from them?

Modern-day birds descended from a group of dinosaurs called theropods.

One of the most famous theropods, the Tyrannosaurus rex, has a hind leg that resembles a large chicken leg. It has four large toes, three pointing forward and one pointing backward, and each is tipped with sharp, curved claws that are compressed from side to side.

More than 250 traits and traits found in the skeletons of theropod dinosaurs and birds are shared by both species.

Like its much larger cousin T, Archaeopteryx, the first bird-like ancestor found, had a long tail and teeth. rex. However, it also exhibited feathers and what appeared to be wings on its forelimbs.

Additionally, according to Dr. Paul Willis, a palaeontologist with ABC’s Catalyst program, it was most likely warm-blooded.

Numerous theropods that resembled birds and had basic downy feathers and hair-like structures can be seen in the fossil record. Willis states that since they were primarily small organisms, “they must have produced their own body heat and evolved hairs and feathers to help retain the body heat they generated.”

Animals have developed two ways to maintain their body heat. One way to produce body heat is through internal thermoregulation; endothermic animals, like birds, use this technique. The alternative is for these ectothermic animals, like reptiles, to absorb heat from their surroundings and store it inside of them.

However, ectothermic animals can still have warm blood despite the fact that we consider them to be cold-blooded. Additionally, their likelihood of maintaining a warm body temperature increases with size.

Because of their larger body mass, larger cold-blooded animals don’t lose as much heat at night as their smaller counterparts, according to studies on crocodiles, a distant relative of dinosaurs. “.

This phenomenon is known as gigantothermy, in which the larger one gets, the easier it is to retain heat.

According to Willis, this means that all large dinosaurs had warm blood by definition.

He continues, “In fact, since heat storage capacity increases with size, eliminating heat and maintaining body temperature must have been a problem for really big dinosaurs.”

Mass extinction event also triggered switch to warm-bloodedness in both mammals and birds

how did birds become warm blooded

The greatest extinction event in Earth’s history may have caused the ancestors of mammals and birds to simultaneously evolve warm-bloodedness and the capacity to walk upright, according to new research.

Earth was experiencing the Permian-Triassic mass extinction event some 250 million years ago. The majority of life on Earth was wiped out by massive volcanic eruptions that caused catastrophic global warming and ocean acidification.

“The scale of this extinction was huge. Only roughly one in twenty of the current species remain, and these were primarily smaller creatures, paleontologist Mike Benton told Quirks. “The survivors were quite few and far between. “.

These survivors included the progenitors of modern mammals and birds. By examining hundreds of fossilized footprints from both before and after this turbulent period of history, Benton discovered proof that these creatures rapidly underwent an evolutionary transition to become warm-blooded and to assume upright postures. This made them possible for them to become the prevailing animals that we know today after the extinction.

Warm-bloodedness key to success

Land life was different prior to the Permian-Triassic mass extinction event. The largest land animals resembled modern-day lizards and salamanders in their sprawling posture, cold-bloodedness, and protruding arms and legs.

“Life was going on well, but to our eyes, we might have thought this was a bit slow. Theyre kind of plodding around at a slow pace,” said Benton, a professor of paleontology at the University of Bristol.

The fossil record has shown an amazing explosion in animal diversity following the extinction, including the emergence of the earliest proto-dinosaurs and the ancestral lineage that gave rise to mammals. It is now thought that at that time, both of these lineages rapidly shifted toward warm-bloodedness. However, it also appears that they changed their posture simultaneously and in a connected manner.

how did birds become warm blooded

Benton discovered that prior to the extinction event, animals exhibited a sprawling, lizard-like posture by examining fossilized trackways. But afterwards, the pattern of footprints changed. Similar to how modern horses, dogs, cats, and even humans walk, the ancestors of both birds and mammals walked with their legs directly beneath them. This was a more upright stance.

In biology, the ability to walk erect is associated with warmbloodedness because both promote stamina and effective movement. Animals are able to run more efficiently due to the biomechanical efficiency of this posture. That being said, an active metabolism is necessary to fully benefit from it.

“Theres a link between upright posture and fast movement. You require a lot of food, so you need the warm bloodedness. A lot of oxygen is required to power the internal engine. And given that they date all the way back to this moment in time, it appears that this is also the case for dinosaurs, birds, and their ancestors,” Benton stated.

Scientists previously believed that this transition had occurred somewhat later in the lineage of birds and dinosaurs. The fact that the evidence indicates that this occurred in the progenitors of both birds and mammals at the same time was unexpected.

He said, “Those who had the good fortune to maintain an upright posture were able to run a little bit farther and a little bit faster.” And I have a suspicion that once a few of them started acting honorably and with warmth in their hearts, they eliminated the others who could not keep up. “.

FAQ

Why did birds evolve to be warm-blooded?

It has been hypothesized that warm-bloodedness evolved in mammals and birds as a defense against fungal infections. Very few fungi can survive the body temperatures of warm-blooded animals. By comparison, insects, reptiles, and amphibians are plagued by fungal infections.

How did warm-bloodedness evolve?

The first warm-blooded animals appeared abruptly 233 million years ago, according to clues hidden deep inside their ears. Before now, scientists estimated that warm-bloodedness, or endothermy, gradually evolved over a period of about 120 million years based on vague clues from animals’ skeletons and their environments.

Why are birds not cold-blooded?

It generates heat by burning the food you eat. All mammals and birds are capable of generating this internal heat and are classed as homoiotherms (ho-MOY-ah-therms), or warm-blooded animals.

When did birds become endothermic?

The fossil record indicates that modern bird orders were fairly well-defined by about 60 My (25), therefore avian endothermy is likely to have been fully developed by about Late Cretaceous-Early Tertiary Periods.