Why fresh water fishes pass dilute urine?
what is " Meroblastic clearage" ?
Freshwater fishes pass dilute urine to maintain osmotic balance in their bodies. Since freshwater fishes live in an environment with lower salt concentration than their own bodily fluids, they tend to absorb water through their gills and skin. As a result, they continuously take in water, causing their bodies to become more diluted. To prevent excessive water absorption and maintain a balanced internal environment, freshwater fishes excrete large amounts of dilute urine to eliminate the excess water and maintain a proper concentration of salts and other solutes in their bodies.
Regarding your second question, "meroblastic cleavage" refers to a specific type of cell division that occurs during animal embryonic development. This term is commonly used in the context of eggs that contain a large amount of yolk, such as bird eggs. In meroblastic cleavage, only a portion of the egg undergoes division, while the heavily yolked part remains relatively untouched. This partial division occurs due to the presence of the yolk, which restricts cell division to smaller, disc-shaped areas called blastodiscs.
Meroblastic cleavage is different from holoblastic cleavage, which is the type of cell division observed in eggs with relatively little or no yolk. In holoblastic cleavage, the entire egg undergoes complete division.
In summary, meroblastic cleavage is a specific type of cell division that occurs during embryonic development and is characterized by partial division of the egg, primarily found in eggs with a large amount of yolk like bird eggs.