Mitochondria and chloroplasts

Every plant and animal has mitochondria. Plants also have chloroplasts. You’re a habitat for trillions of bacteria. You need each other.

There are three main groups of life, unless you count viruses as alive. The bacteria are very small single cells that permeate every possible nook and cranny, even down into the crust of the planet. Archaea are larger and tend to hang out in odd places. At some point an archaea-type cell engulfed a bacteria without killing it. That bacteria started making ATP (energy molecules) for the host cell. The symbiotic pair is called a eukaryote and the bacteria is called a mitochondrion. Further down the road, a eukaryote engulfed a cyanobacteria, which could use sunlight to make sugar out of thin air. That bacteria is now called a chloroplast. Eventually the eukaryotes started forming colonies. The ones with only mitochondria (plural of mitochondrion) are animals, the ones with chloroplasts too are the plants.