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!
Answer:
TT
All tall
Explanation:
If an organism is purebred, that means it is homozygous. That means, it contains two copies of the same allele (trait) at this particular gene. Lets denote the tall allele as T. That means the plant is TT, and purebred tall.
No matter what genotype (i.e. what 2 alleles) another plant has, the offspring will always be tall. That is because it will always inherit one T from the TT parent. Even if we cross it to a tt plant, all the offspring would be Tt. They would be heterozygous, but they would be tall.
Answer:
The left side of the heart receives oxygenated blood from the pulmonary vein and pumps it into the aorta, while the right side of the heart receives deoxygenated blood from the vena cava and pumps it into the pulmonary vein. The pulmonary vein and aorta also have valves connecting them to their respective ventricle.
Explanation:
Answer:
The speed at which the reactants change to products over a given time.
Explanation:
A chemical's <u>reaction rate</u><u> is the change in the concentration of a reactant or a product with time (in moles per second)</u>.
Remember that during a chemical reaction, reactants are converted to products. Or what is the same, products are formed at the expense of reactants. This can be represented:
reactants → products
Therefore,<u> the progress of a reaction can be followed measuring the decrease in concentration of the reactants or the increase in concentration of the products.</u>
According to the temperature and other parameters, the reaction rate can increase or decrease.
