Why humans need organs, like the liver and pancreas, but amoebas do not.

They have no use for it, just like they dont have any type of respiratory organs like lungs.

Explanation:

In the case of nutrition and digestion they obtain food by capturing their prey with their pseudopodia. The food is internalized through a type of endocytosis known as phagocytosis. Nutrients are obtained as the enzymes digest the food inside the vacuole and when they are finished the food vacuole dissolves.

answer: ice crystals in air

the water from the water body or another source of water gets evaporated as water vapor as an effect of heat on water. these water vapor rises in the upper layers of the earth atmosphere under high atmospheric pressure. the atmospheric pressure of these water molecules starts to decrease due to the effect of cold air. the invisible water vapor condenses into visible water droplets and ice crystals.these ice crystals and water droplets being less denser than the surrounding air floats on air as clouds.