What does it mean to be selectively or semi-permeable

Selectively permeable or semipermeable means specific substances are allowed to pass through the plasma membrane.

Explanation:

The plasma membrane is selectively or semipermeable in nature because the plasma membrane allow only specific molecules such as nonpolar substances or hydrophobic substances such as steroidshormone to pass through it and prevent the passage of polar solute molecules such as water,glucose.

   To transport these polar solutes across the membrane an additional protein is needed in case of transport of water channel protein is needed whereas in case of glucose transport carrier protein is required.

answer: tributaries flow into rivers.

wetland is a biome that develops when the water gets accumulated in a land exhibiting a huge depression. these form either seasonally or permanently. the water in the wetland comes from rivers, lakes, ocean, flood, rain or other sources. the wetlands includes mangroves, marshes and peatland.

tributaries flow into the rivers develops a wetland because such water will get deposited in the depression and will restrict the original flow of tributary water. hence, water with low drainage current combines with the river water.

a. to encourage apoptosis