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Course: AP®︎/College Biology > Unit 8
Lesson 6: Disruptions to ecosystems- Mutation as a source of variation
- Introduced species and biodiversity
- Invasive species
- Human activities that threaten biodiversity
- How does climate change affect biodiversity?
- How did all dinosaurs except birds go extinct?
- Were dinosaurs undergoing long-term decline before mass extinction?
- Human impact on ecosystems review
- Disruptions to ecosystems
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How did all dinosaurs except birds go extinct?
The extinction of non-avian dinosaurs except birds at the end of the Cretaceous has intrigued paleontologists for more than a century. One theory is that an asteroid impact 65 million years ago off the coast of Mexico generated massive tsunamis, with impact debris cutting off sunlight for months, stopping photosynthesis and causing freezing temperatures. Chemical reactions in the atmosphere caused acid rain and long-term global warming, all of which extinguished non-avian dinosaurs. However, at the same time, massive lava flows erupted across what is now southwest India. The eruptions probably caused many of the same effects as the asteroid impact. Although most scientists believe that the impact was the final blow for non-avian dinosaurs, both events could well have played a role. Created by American Museum of Natural History.
Want to join the conversation?
- how did birds survive this?(5 votes)
- Being small helped the bird and mammals. Having lower energy requirements is good in times of scarce food. Being warm-blooded may have helped is the climate was changing a lot, though that comes at a cost of needing more food. Being able to fly would have helped in moving between scarce food resources.(12 votes)
- Then why is there no flying dinosaurs?(1 vote)
- Evolution and natural selection takes its own path, the asteroid impacts, volcanic eruptions and other catastrophes also impact it. As a result there are no flying dinosaurs left in the wild. But this may not surprise you... The "flying dinosaurs" of today are called birds! As I think that birds did evolve from a type/group of dinosaurs called the theropods.(2 votes)
- when the asteroid hit there were about 1 species of mammals and they didn't even survive but the birds survived because of the aquatic reptiles because if u look back further into history they evolved from bacteria and then aquatic animals so that means the aquatic reptiles survived barely and they evolved over time to suit there new environment. So if there were no dinosaurs then the genetic code for them were replaced ignorer to make mammals(1 vote)
- Is there a crater where the meteor hit today?(1 vote)
- Yes, there. is a crater. It is in Mexico. That is what led to the meteor theory.(1 vote)
- Wait, so birds have a common ancestor with flying type dinosaurs (forgot the name)?(1 vote)
- Yes, the surviving flying dinosaurs evolved into the birds we know today. You may be thinking of the Pterodactyl. I think it is the most famous example of a flying dinosaur.(1 vote)
- what does instatameos mean?(0 votes)
- I take it you mean "instantaneous". It means 'instantly' or 'suddenly'. 'Less than a second'.
Something like that.(1 vote)
- Seriously? The birds-are-related-to-dinosaurs theory?
Dinosaurs were reptiles, cold-blooded; birds are warm-blooded. Stupid Evolutionists...(0 votes)- Please learn a bit more about evolution and dinosaurs before criticizing an idea. Also do not call people names.
There were avian and non-avian dinosaurs. While name dinosaur does come from "terrible lizard" dinosaurs early dinosaurs were not lizards. Dinosaurs and lizards had a common ancestor about 270 million years ago.(7 votes)
- how did the birds survive the extinction.(0 votes)
Video transcript
The question of non-bird dinosaur
extinction is really an open one, I mean certainly that there's a tremendous
amount of evidence, in fact that there's no doubt that at the time the dinosaurs went extinct a large meteorite or asteroid hit the
planet somewhere off the Yucatan Peninsula in Mexico. However, directly tying this event to the disappearance of the terestrial fauna is very difficult and that's just because our sample is so
small there's only a couple places in the world
where both dinosaur fossils as well as evidence of the impact are preserved both of those are in western North America, so we don't know whether it was an
instantaneous event we don't know whether the dinosaurs in
the southern hemisphere, like held on for millions of years afterwards, we just
don't have the record to be able to determine that. One thing we do know though, is that certainly that the dinosaurs, non-bird dinosaurs appear to be coming more and more rare, less common as you approach the time when the meteroite hit about
sixty five point four million years ago so that it's not like everything was
going great, and then you just had this massive cataclysmic
event and everything disappeared, we know that stuff was changing, stuff
was changing quickly. At the same time there was a huge amount of volcanic activity especially from places in
western India, and interestingly enough this coincides with around the time of
the asteroid impact so many paleontologists feel that it was a combination of
factors, maybe both asteroids and volcanos that did the non-bird dinosaurs in,
and I should emphasize not just that non-avian or non-bird dinosaurs but
many many other animals and plants, in fact we estimate that maybe as much as seventy-five percent of
all the species that lived on the earth at that time went extinct during this
very dramatic event.