When something needs to be transported against its concentration gradient, or a molecule is too big to simply diffuse through a membrane, active transport has to be used. So active transport requires energy (ATP).
Examples:
1. Antiport pumps: transport one substance in one direction while transporting another substance the other way. An example of this is the sodium-potassium pump.
2. Symport pumps - uses a substance that wants to move from an area of high concentration to low concentration and carries another substance against its concentration gradient. An example of this is the sodium-glucose transport protein
3. Endocytosis - large amounts of extra cellular fluid can be taken into a cell - needs ATP to bind proteins in the cell membrane and causes them to change their shape...which eventually causes the surrounding of the fluid to be brought in (a vesicle).
4.exocytosis - opposite of above
Answer:
survive in their environment
Explanation:
According to Darwin's theory of evolution, natural selection is the main mechanism. Darwin explains that organisms that have heritable traits that help them survive and reproduce, will be favorable by natural selection. Those favorable traits will enable organism to better adapt to their environment and to pass more genes on to the next generation (offspring).
Organisms adapt to their environment by changing their behavior, structural traits or physiology as a response to environmental change, so that they become well suited to it.
<span>The California high-speed rail is such a groundbreaking effort because it helps with the environment and makes it cleaner. </span>
It seems that you have missed the necessary options for us to answer this question so I had to look for it. Anyway, here is the answer. Varicose veins seen in the superficial veins of the legs are unsightly and often treated by surgically removing them. however, even without these veins being present, the return of all blood toward the heart from the legs is not diminished primarily because <span>blood can still return via the deep veins. Hope this helps.</span>
