Answer:
The envelope is an outer lipid bilayer that is studded with proteins. The function of the envelope is to identify and bind some receptor sites on the host membranes. After fusing with the cell membrane, it allows to capsid and genetic material to enter the cell and infect it.
Explanation:
Prefer different forms of contact
Because they each get half their dna from both parents. in pea plants for example the offspring have a total of 14 chromosomes thus inheriting 7 from each parent. plus genetic mutation is always a possibility making the offspring genetically different from the parents.<span />
From mouth/nose, the air passes to the trachea (the wind pipe), there it enters (sequentially) the bronchi, bronchioles (small pipe-like structures), alveoli (widened empty sacs), the walls of which are in close contact with the blood vessels which contain the RBCs, which in turn contain the protein--hemoglobin, which binds to the oxygen present in the freshly inhaled air, and loses the carbondioide present DISSOLVED in the blood. This bound oxygen goes to the heart (of course along with the RBCs in the blood), from there to the smaller and smaller arteries, then to the capillaries, where again oxygen is lost to the surrounding tissue fluid, from where the cells collect oxygen by simple diffusion, and lose carbon dioxide, which gets dissolved in the water present in the blood.
From here the blood, with hemoglobin poorer in oxygen, and richer again in carbondioxide goes to the venules, and veins (capillaries continue as venules), which become successively larger to become superior and inferior vena cava and enter the right atrium, and then from there the blood again goes to the lungs and comes in contact with fresh air in the alveoli.
