Answer:
Transportation of substances in cells, where they travel against the concentration gradient. However, it requires ATP to do so.
Explanation:
Isotopes are variants of a particular chemical element which differ in neutron number (neutral particle)and all isotopes of a given element have the same number of protons (positive particle) in each atom.So isotope B of the sodium will have 11 protons, 11 electrons but it may have a wide range in its number of neutrons.
The Phytoplankton <span>support nutrients in water and from the base of many aquatic ecosystems.</span>
The mechanisms of reproductive isolation prevent the reproduction of two individuals from different species. The prezygotic mechanisms disrupt the stages of reproduction before the forming of the zygote or prevent the mating at the start, and the postzygotic mechanisms affect the stages of reproduction after the forming of the zygote.
So, the first and the third example (the urchins and the grasshoppers) show the prezygotic mechanism, as the two individuals are not able to mate or form a zygote.
The second and the fourth example ( zonkey and the death of a zygote) show the working of the postzygotic mechanisms, as the zygote is formed, but it seems to be inviable, and the zonkeys are sterile, preventing the individual to reproduce.
