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>
Answer:
Those capillaries that have endothelial cells tightly attached have an increase in cell-to-cell junctions, such as desmosomal junctions that are poorly permeable to substances.
These capillaries generally function as conductors or collectors and not as permeabilizers like the pulmonary capillaries that are fenestrated and allow a high passage of substances and gases.
The capillaries are waterproof and prevent the passage of substances or fluids such as in the blood-brain barrier that is very selective
Explanation:
The blood-brain barrier is too selective since it is not favorable for the organism that many fluids, drugs, substances or chemical compounds enter the brain space.
This is the reason why the vessels are waterproof and why pharmacology was challenged to invent drugs that could cross this barrier since it was considered impossible.
An example is dopamine, which in parkynson's disease the levo group is added to dopamine, thus forming levodopamine as a product, this is the only way that the drug crosses the blood-brain barrier and can pass the impermeable barrier generated by capillaries with endothelial cells that are close to each other or closely linked
<span>This is false. Everyone is unique in this aspect and although genetics can help you, or make life harder, it also falls down to personal behavior and habits. There are no genetics that can save you from constant overeating and there are no genetics that can prevent you from working out, at least to your possible extent.</span>
