The electrons in the outermost shell of the covalent compounds are shared by nearby atoms. As there are no free electrons for conducting electricity, the covalent compounds are perfect insulators at absolute zero. As the temperature increases, some electrons move from valence band to conduction band. This gives rise to conductivity. But as the numbers of charge carriers are very low, covalent compounds are poor conductors. On the other hand metals are good conductors cause of their bonding. Metallic bonding consists of a sea of electrons rather than discreet bonds. The free electrons are able to move freely. Since electricity and heat need electrons to move, the bonding promotes conductivity.
Robert Hooke is the first person to observe cells as microscopic structures.
He was of British descent and, fun fact, he discovered cells by looking at a sliver of cork under a microscope lens (although the 'fun fact' is heavily simplified).
Vascular tissue is located inside the pericycle of a root, which I believe would be considered the inner layer.
It refers to the cost or benefit of an activity by an economic agent for which it does not pay a price.
Fr ex: factory produces goods , it releases harmful smokes n polluts our enviroment.
In this case externality implies the negetive effect.
Hope it helped u!!
Genetic variation is an important force in evolution as it allows natural selection to increase or decrease frequency of alleles already in the population. ... Genetic variation is advantageous to a population because it enables some individuals to adapt to the environment while maintaining the survival of the population.
