Cells, tissues, organs, and organ systems summary

A cell is the basic unit of life. A group of cells form tissues, and a group of tissues forms organs, and a group of organs form organ systems.

Eukaryotic cells are theorized to have evolved from prokaryotes called the endosymbiotic theory. this explains that the most primitive eukaryotic cell engulfed a prokaryotic cell (by the process of phagocytosis) that is capable of cellular respiration and another prokaryotic cell that is capable of photosynthesis. these prokaryotic cells eventually became organelles and these organelles are the mitochondria and the chloroplast