Cretaceous extinction also known as Paleogene extinction was a period of time when suddenly around three quarter of the animal and plant species began to get extinct from the land. The event happened around 66 million years ago and is considered as the end of cretaceous era that lead to the beginning of Mesozoic era.
Reasons for the mass extinction:
- Scientists think that a major asteroid or comet hit the surface of earth which deteriorated the earth’s environment, especially by making it difficult for plants to perform the process of photosysnthesis. This is called as Impact hypothesis and scientists think that it was the reason of extinction of so many species because they found debris of asteroid in the land.
- There could also be some other reasons like climate changes,volcanic eruptions and changes in the sea level which made the environment unfavorable for the survival of living organisms.
- One of the best known organism that is thought to extinct in cretaceous period was dinosaur.
Extinction of Dinosaurs:
As stated above the exact cause of dinosaur extinction can not be stated with confidence. This is because cretaceous period was the time when so many unfavorable circumstances took place like diseases, geologic events ,climate change etc.
However, the most believed theory is that some Asteroid hit the surface of earth and turned the climate very very old. Therefore, those amazing creatures were not able to survive that climate.
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Answer:
A downhill
Explanation:
A runoff happens when water drags sediment from a rock over a sloping terrain. Thus, water drags the eroded fragments of a rock in favor of gravity, pushing these fragments downwards. This is very common in mountainous and steep regions, without vegetation cover, where erosion caused by runoff is very high.
"(1) Human population growth reached 6.8 billion in 2010 and it continues to increase" is what led to the other <span>three, since all of these happen from human activity. </span>
Question 5 is all of the above question 6 is bases that are found on dna question 7 is the one on the top
