Because the sun is really hot and we'd die if they weren't there
Answer:
Scientists believe that the different types we know emerged as early humans adapted to infectious diseases.
Explanation:
Different human blood types probably emerged to ward off infectious diseases. The incompatibility of some blood types, however, is only an "accident" of evolution. But this is a relatively recent problem, since blood transfusion has been around for only a few hundred years.
There are four main blood types. The oldest is B, which must have originated about 3.5 million years ago - it existed even before the human species evolved from its hominid ancestors, from a genetic mutation that modified one of the sugars in the surface of red blood cells.
Approximately 2.5 million years ago, mutations inactivated sugar, resulting in type O blood, which has neither type A nor B. sugar. AB blood, as it is easy to suppose, is covered by both sugar A and sugar by B.
Answer:
Homeostasis is the process of maintaining a constant internal environment of the body with the help of certain mechanisms such as feedback loops.
Explanation:
Homeostasis refers to the maintenance of a relatively constant internal environment of the body. It includes maintaining several parameters such as acid-base balance, blood glucose level, body' temperature, etc. within the narrow range.
Homeostasis is mainly maintained with the help of negative feedback loops wherein the deviation of any parameter from the normal physiological range is counteracted and restored.
For example, the blood glucose level remains within the range of 70 and 110 milligrams of glucose per 100 milliliters of blood under normal physiological conditions. Any deviation from the range is restored with the help of pancreatic hormones insulin and glucagon.
A, their cells have cell walls
Organisms belonging to the plant kingdom are eukaryotic and multicellular organisms. They have a distinct cell wall made of cellulose. Cells are organised into true plant tissues. ... Important examples of plants are mosses, ferns, conifers and flowering plants.
Heat from the Sun causes water to evaporate from the surface of lakes and oceans. This turns the liquid water into water vapor in the atmosphere. Plants, too, help water get into the atmosphere through a process called transpiration! ... Water can also get into the atmosphere from snow and ice.
