Answer:
Covalent bonds are the types of Bond which is formed by sharing of an electron between two atoms of same element or two different elements. The bond which is formed by the completely lost or gained of an atom is known as ionic bond.
Explanation:
The most common example of covalent bond is formed from carbon atom. The valence of carbon atom is 4. Therefore, it is very hard to gain or lose an electron from the carbon atom. Therefore, the carbon tends to share the electron instead of completely losing or gaining the electron.
Ionic bond is very common and it can be formed by many elements from the periodic table. Ionic bond is more stable and stronger when compared to the covalent bond in nature.
Answer:
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Explanation:
The main treatments for cancer are radiation, surgery, and chemotherapy.
Answer:
a prezygotic barrier
Explanation:
Both wild tigers and lions are said to be reproductively isolated.
Reproductive isolation is defined as the existence of barrier between organisms of different species such that they cannot reproduce.
The mechanisms of reproductive isolation varies. While some act to prevent the formation of zygotes (in case of mating) between organisms of different species, some ensures that the resulting zygotes are invalid.
Reproductive isolation mechanisms that act to prevent fertilization and formation of zygotes are referred to as prezygotic mechanisms while those that ensure that invalid zygotes result (in case of successful fertilization) are referred to post zygotic mechanisms.
<em>The natural differences in the ranges of wild tigers and lions ensure that both animals do not mate with each other, let alone results in zygote. This is a form of pre-zygotic reproductive isolation mechanism.</em>
