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.
Hope it help!
The correct answer is A.
Oswald Avery applied several biochemical techniques to large cultures of bacteria in order to extract and purify the "transforming principle". Their experiments showed that most probably the "transforming principle" was DNA. One of the observations leading to this conclusion was that enzymes that degrade proteins or RNA (such ribonucleases) had no effect on the "transforming principle". On the contrary, enzymes degrading the DNA destroyed the extract's transforming capacity.
Answer:
Most of the world's deserts are located near 30 degrees north latitude and 30 degrees south latitude, where the heated equatorial air begins to descend
Explanation:
Answer:
°Draws attention to the magnitude and importance of threatened biodiversity.
°Identifies and documents those species most in need of conservation action.
°Provides an index of the decline of biodiversity.
Establishes a baseline from which to monitor the future °status of species.
A hemopheliac is someone with a bleeding disorder resulting from any missing clotting factors in their blood. Vasoconstriction isn't generally the problem in hemophiliacs, nor is it the destruction of pathogens. If fibrin threads are not present to help form the platelet plug, then excessive bleeding occurs. Fibrin is one clotting factor that a hemophiliac may be missing which is then causing the disorder.
