奇妙的水TPO 30 Lecture 2 Paleontology《呼吸过度》
偶题Narrator
Listen to part of a lecture in a paleontology class.
Professor
As we’ve discusd, birds are apparently descendants of dinosaurs and shared many commonalities with some dinosaur species, um...feathers and maybe even flight and of cour egg laid. OK.
So, many paleontologists, mylf included, have wondered about other similarities between dinosaurs and birds. Since adult dinosaur fossils have sometimes been discovered near or on top of nests, we’ve been looking at the dinosaur parenting behavior.
Student
Parenting behavior, well, that sounds so gentle and caring. But dinosaurs were ferocious reptiles and reptiles don’t take care of their young, do they?
Professor
Well, some reptiles incubate their eggs, crocodiles do. And as for popular attitudes well, take the Oviraptor for instance.
In the 1920s, a paleontologist discovered the fossil remains of a small dinosaur near a nest containing eggs. He assumed the dinosaur was stealing the eggs, so he named it Oviraptor that means egg thief in Latin, which fueled the generally negative public image of such dinosaurs.
But by the 1990s, other experts had convincingly made the ca that instead of robbing the nest; the Oviraptor was probably taking care of the eggs. You e, dinosaurs’ clost living relatives – birds and crocodiles – display nesting behavior. And dinosaur fossils have been found in postures that we now believe to indicate brooding behavior, that is, sitting on the eggs until they hatch.
So we are cur
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ious about the type of care dinosaurs gave to their young. And we’d like to figure out which dinosaur parent, the male or the female gave the care.
Student
Shouldn’t the behavior of crocodiles and birds give us some clues then?
Professor
Well, with crocodiles, it is the female who guards the nest, and with birds, it depends on the species, it can be the male or the female that takes care the eggs, or both. In over 90 percent of all bird species, both parents take care of the eggs and the young birds.
Student
But sometimes it’s just the male?
Professor
Well, exclusive care by the male parent is much less common, but it does occur. Now, for animals other than birds, the care of young by both parents is pretty unusual in the animal kingdom. Males contribute to parental care in fewer than five percent of all mammalian species. It’s even less frequent among reptiles. And exclusive care by the male is very rare. So rearchers have wondered about the evolution of male parenting behavior in birds for quite some time. And now there’s rearch showing that for some of the birds’ dinosaur relatives, it’s likely that the male parent was also in charge of taking care of the eggs.
Student
How did they figure that out?
Professor
Well, first they looked at clutch volume, that’s the number of eggs in the nest of crocodiles, birds and three types of dinosaurs, including Oviraptors that are thought to be cloly rela简单的才艺表演
虚拟光驱怎么安装>木耳冬瓜三鲜汤>钢结构工程施工ted to the dinosaur ancestors of birds.
So when rearchers examined fossilized remains of nests, th
ey found that the dinosaurs had larger clutch volumes, more eggs in the nests that is, than most of the crocodiles and birds that were studied. But, and this is important, their clutch volumes matched tho of birds that have only male parental care. You e, bird species in which only the males take care of the nest tend to have the largest clutches of eggs.
Student
So what’s the connection between bird and dinosaur behavior?
Professor
Well, rearchers now believe, becau of this study, that the male parenting behavior of the birds might have its origins in the behavior of dinosaurs.
Student
Bad only on evidence of clutch volume size, the number of eggs?
Professor
No, there’s more. They also examined the fossilized bones of tho three types of dinosaurs that were found on or near nests to determine their x. You e, adult female birds during egg production produce a layer of spongy bone tissue inside certain long bones. And so did female dinosaurs of the kinds that were investigated. This spongy tissue rves as a source of calcium for eggshell formation. But when the dinosaur fossils were examined, there were no spongy bone deposits.
Student
Meaning that tho dinosaurs on the nests were probably adult males who wouldn’t have needed calcium for making eggshells.
Professor
Exactly. And then there’s this: birds like the kiwi, the ostrich and the emu; they share certain physical characteristics with the dinosaurs. And interestingly, they also show a consistent pattern of nest care by the male.
