Answer:
India was a separate continent until 45 million years ago
Explanation:
India was part of the Gondwanaland continent which was one of the two remnants of Pangaea, while Asia was part of Laurasia, the other remnant of Pangaea. Because these two land masses were separate, the animals and plants were evolving separately for millions of years. India further separated from Gondwanaland, and it was actually a very large island for millions of years, resulting in isolation and development of unique animals and plants because of it. As India was moving it reached Asia and collided with it, thus becoming one land mass. Some Asian species managed to get in India, but mostly in its northern parts, while the central and southern parts remained dominated by the indigenous species. The Himalayan Mountain Range that formed because of the collision also helped in preserving lot of the indigenous species as it became a natural barrier that most species can not go through.
Answer:
For both actin and microtubule polymerization, nucleotide hydrolysis is important for decreasing the binding strength between subunits on filaments.
Explanation:
Cytoskeletal filaments are common to eucaryotic cells and are impotartant to the spatial organization of cells. Intermediate filaments provide mechanical strength and resistance to shear stress. Microtubules determine the positions of membrane-enclosed organelles and direct intracellular transport. Actin filaments determine the shape of the cell's surface and are necessary for whole-cell locomotion. A large number of accessory proteins are present that link the filaments to other cell components, as well as to each other. Accessory proteins are essential for the assembly of the cytoskeletal filaments in particular locations, and it includes the motor proteins that either move organelles along the filaments or move the filaments themselves.
Actin filaments and microtubules are assembled with expenditure of energy i.e the ATP/GTP tightly bound to actin/tubulin is irreversibly hydrolyzed to ADP/GTP during the assembly process, and liberation of Pi in the medium occurs subsequent to the incorporation of subunits in the polymer. Pi release acts as a switch, causing the destabilization of protein-protein interactions in the polymer, therefore regulating the dynamics of these fibres. The progress is made in four areas: the chemistry of the NTPase reaction; the structure of the intermediates in nucleotide hydrolysis and the nature of the conformational switch; the regulation of parameters involved in dynamic instability of microtubules; and the possible involvement of nucleotide hydrolysis in the macroscopic organization of these polymers in highly concentrated solutions, compared with the simple case of a equilibrium polymers.
"Water depth" is the factor among the choices given that has the <span>greatest importance in determining the characteristics of an aquatic ecosystem. The correct option among all the options given is the second option.
</span>
