Answer:
When you sit on a plane for 6 hours without moving, blood accumulates in your veins, and the moment you get up, gravitational forces affect venous return, cardiac output, blood pressure, and venous pressure. That way, when you're sitting on a plane, the gravitational force is the same at the upper and lower extremities, such as the chest, abdomen, and legs, causing venous blood pressure and volume to be evenly distributed throughout the body. However, when one gets up, one becomes dizzy because of abnormal regulation of blood pressure. This is because gravity causes blood to accumulate in the lower extremities (veins of the legs and trunk). This lowers the blood pressure and the blood that the heart pumps. By causing blood to accumulate in the lower extremities, and as venous compliance increases, the veins expand with blood that causes the volume of blood to shift in the veins. This increases the volume and venous pressure in the lower extremities when standing. And the volume of thoracic venous blood is less and less central venous pressure. This leads to a decline in stroke volume. Cardiac output and mean arterial pressure also decrease as left ventricular stroke volume decreases, reducing pulmonary venous return. Decreased standing blood pressure, referred to as orthostatic or postural hypotension. Thus, lowering blood pressure decreases cerebral blood flow, which means less range of blood in the brain causing dizziness.
Explanation:
The hormone ethylene is a gas and disperses easily.
Question 1 The world's population is spread very unevenly. Some spaces are empty or very sparsely populated: we speak of human deserts:
• Cold polar environments are the least populated regions: the ground, frozen permanently, prevents any form of agriculture, the very low temperatures make the habitat difficult.
• The hot or cold desert environments are also not busy: the lack of rain and the strong heat during the day limit the activities of men. The only exceptions are oases.
• The role of relief is more difficult to define. High temperate mountains like the Alps are generally sparsely populated but tropical chains like the Andes have a high population density. However, men have generally settled in the plains, in the valleys (along with the rivers) and on the coasts.
There are also other factors unrelated to land factors that influence population density such as job availability, or even historical factors.
Question 2: Birth rate:
The birth rate (sometimes called the crude birth rate) is the ratio of the annual number of births to the average total population for that year. When the population grows, the contact between people will be more permanent, and it will increase the marriage rate, and thus the birth rate. Age structure:The age structure is a mode of graphical representation of the structure (of age as well as of sex) of a population which constitutes a synthetic image of the past, present and future of the population.When a population resides for a long time in the same place (in favorable conditions, not raising the death rate and without moving), this will vary the age structure by observing an increase in the elderly population.
in lakes or wetland such as marshes or swamps
The answer to this is C. polygenic<span> i know for a fact</span>
