Answer: More than 99 percent of all organisms that have ever lived on Earth are extinct. As new species evolve to fit ever changing ecological niches, older species fade away. But the rate of extinction is far from constant. At least a handful of times in the last 500 million years, 75 to more than 90 percent of all species on Earth have disappeared in a geological blink of an eye in catastrophes we call mass extinctions.
Though mass extinctions are deadly events, they open up the planet for new forms of life to emerge. The most studied mass extinction, which marked the boundary between the Cretaceous and Paleogene periods about 66 million years ago, killed off the nonavian dinosaurs and made room for mammals and birds to rapidly diversify
Their population will either decrease or they will be forced to migrate. They may also undergo adaptive radiation to adapt to new food sources or environments.
In comparison to the discrepancy model,
the response to Intervention model assesses the complexities of learning
disabilities better than a one-step process where an individual is tested once
and diagnosed. Learning disabilities are conditions that cause difficult
experience in learning.
