AP BIOLOGY

Detailed explanation-1: -Intercellular communications in multicellular organisms arise via four different molecular mechanisms: (1) cytoplasmic bridges, (2) exosomes and ectosomes, (3) direct interactions between membrane proteins of adjacent cells, and (4) soluble messenger molecules (mediators) controlling more or less distant target cells.

Detailed explanation-2: -Both unicellular and multicellular organisms undergo mitosis.

Detailed explanation-3: -Direct signaling (also called juxtacrine signaling) involves communication between cells that are in direct contact with each other. This communication is often mediated by gap junctions in animal cells and plasmodesmata in plant cells. Autocrine singaling occurs when a ligand acts on the same cell that releases it.

Detailed explanation-4: -Within-cell signaling allows bacteria to respond to environmental cues, such as nutrient levels, some single-celled organisms also release molecules to signal to each other.