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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To maintain a line of pure-breeding peas, selective breeders would use a technique called artificial cross-pollination. This is a technique were breeders transfer pollen from the anthers of one pea plant (male parent) to a stigma of a flower (female parent).
This technique was developed by Gregor Mendel, the founder of the science of genetics. He was a monk who dedicated his time in research about how genes of plants are carried over through specific species. In his controlled experiment he used the pea plant because they are cheap and readily available from merchants who sold them in different classifications. He also used pea plants because they have the capacity to self-pollinate or cross-pollinate.
The answer is Chordates
Chordates belong to the pylum Chordata of the Animal Kingdom.They have the following characteristics;
Lower vertebrates have a notochord which is a hollow nerve chord that is located dorsally of the animal while higher vertebrates have a vertebral column of bone and cartilage. They have a coelom which is a body cavity that differentiates higher vertebrates into organs and digestive tract.
Answer: They move during that time because of the fact that the earth move around one its axis around the sun.
Explanation:
Organ. An organ is a system of tissues that work together on a larger scale to do certain jobs within an animal's body. Examples of organs are the brain, heart and lungs. Anatomy is an example of a biology specialty concerned with this level.
