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.
The f1 generation may have genes for short plants just that the genes for long plants are dominant over the genes for short plants(recessive) so when cross pollination happen and that two f1 long plants which are homozygous cross pollinate, the recessive genes have a chance of being paired up in new offspring(F2 offspring) thus the possiblity of short plants in f2 generation
This is false. Gross production is the total production that occurs before cellular respiration, or any net loss of energy occurs. It is impossible to maintain this initial amount of energy, however.
