Answer:
Hidden nicely against its background, an animal can escape its enemies for another day. The particular colors on an animals are determined partly by the genes its gets from its parents. That means that genes that hide animals can spread thanks to natural selection, leading to the evolution of exquisite camouflage.
Explanation:
Answer:
Once the oxygen diffuses across the alveoli, it enters the bloodstream and is transported to the tissues where it is unloaded, and carbon dioxide diffuses out of the blood and into the alveoli to be expelled from the body. Although gas exchange is a continuous process, the oxygen and carbon dioxide are transported by different mechanisms.
Transport of Oxygen in the Blood
Although oxygen dissolves in blood, only a small amount of oxygen is transported this way. Only 1.5 percent of oxygen in the blood is dissolved directly into the blood itself. Most oxygen—98.5 percent—is bound to a protein called hemoglobin and carried to the tissues.
Hemoglobin
Hemoglobin, or Hb, is a protein molecule found in red blood cells (erythrocytes) made of four subunits: two alpha subunits and two beta subunits (Figure 20.19). Each subunit surrounds a central heme group that contains iron and binds one oxygen molecule, allowing each hemoglobin molecule to bind four oxygen molecules. Molecules with more oxygen bound to the heme groups are brighter red. As a result, oxygenated arterial blood where the Hb is carrying four oxygen molecules is bright red, while venous blood that is deoxygenated is darker red.
Answer:
D- Topsoil, Subsoil, and Parent Soil
Answer:
c. A piece of mesh, keeping some things out and letting some things in
Explanation:
The cell membrane of a cell is described as "selectively permeable". Permeable means things can go through it, but the word selectively is the important part. It lets things in, but it also keeps things out. This way it can regulate the different things that go in and out of the cell. It allows certain molecules that provide the cell nourishment and other things that help it function, and at the same time, it allows waste to move out of the cell. Not all needed molecules can go through the "mesh-like" membrane, that why some of them need help.
