Secretion into the tubular fluid occurs when principle cells in the pct secrete h+ into the urine when the principle cells in the dct and collecting ducts reabsorb na+ and secrete k+ when the cells in the loop of henle become impermeable to water never occurs at all

Veins have a much lower blood pressure than arteries. which of these prevents backflow of blood in veins? a. pressure applied by the heart b. one–way valves in veins c. thin muscular walls of veins

In meiosis ii during anaphase ii which structures separated homologous chromosomes or sister chromatids

Monarch butterflies have brightly colored orange wings with black patterns on them, making them easily visible to birds that eat butterflies and moths, yet birds rarely eat the monarchs. likewise, the monarch caterpillars are brightly striped yellow and white and black, and they also are rarely eaten by birds, although some wasps will attack them and feed them to their young. what can be inferred from these observations? monarchs must threaten and attack birds, but not wasps. monarchs have a way of discouraging bird predation that does not involve hiding. monarchs’ wings are so colorful that most birds must find them difficult to eat. monarchs lay more eggs than other less conspicuous butterflies.