Before plants could colonize land, something had to become plants! From Wikipedia: I will not edit this article, but I might create a simpler one. They want those for wikimedia commons, but I want it for the standard!
Procaryote cells have no nucleus or chromosomes, and they are much smaller than plant or animal cells. They are the bacteria and relatives of bacteria, and are very abundant and diverse in the world.
Emergence of eukaryotes[edit]
Main article: Hypotheses for the origin of eukaryotes
Modern taxonomy classifies life into three domains. The time of the origin of these domains is uncertain. The Bacteria domain probably first split off from the other forms of life, but this supposition is controversial. Soon after this, by 2 Ga,[89] they split into the Archaea and the Eukarya. Eukaryotic cells (Eukarya) are larger and more complex than prokaryotic cells (Bacteria and Archaea), and the origin of that complexity is only now becoming known. (Starting around 1996).
Around this time, the first proto-mitochondrion was formed. A bacterial cell related to todays Rickettsia,[90] which had evolved to metabolize oxygen, entered a larger prokaryotic cell, which lacked that capability. Perhaps the large cell attempted to digest the smaller one but failed (possibly due to the evolution of prey defenses). The smaller cell may have tried to parasitize the larger one. In any case, the smaller cell survived inside the larger cell. Using oxygen, it metabolized the larger cells waste products and derived more energy. Part of this excess energy was returned to the host. The smaller cell replicated inside the larger one. Soon, a stable symbiosis developed between the large cell and the smaller cells inside it. Over time, the host cell acquired some of the genes of the smaller cells, and the two kinds became dependent on each other: the larger cell could not survive without the energy produced by the smaller ones, and these in turn could not survive without the raw materials provided by the larger cell. The whole cell is now considered a single organism, and the smaller cells are classified as organelles called mitochondria.[91]
A similar event occurred with photosynthetic cyanobacteria[92] entering large heterotrophic cells and becoming chloroplasts.[85]:6061[93]:536539 Probably as a result of these changes, a line of cells capable of photosynthesis split off from the other eukaryotes more than 1 billion years ago. There were probably several such inclusion events. Besides the well-established endosymbiotic theory of the cellular origin of mitochondria and chloroplasts, there are theories that cells led to peroxisomes, spirochetes led to cilia and flagella, and that perhaps a DNA virus led to the cell nucleus,[94],[95] though none of them are widely accepted.[96]
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This article does not address directly where the Chromosomes come from! The reason for that is very good. It can't yet be proven that they came from a similar endosymbiotic event that postulates a spirochete invaded the cell which had mitochondria in it. Proof of this may be found in the structure of the chromosome compared with the structure of the spirochete bacteria. Some as yet unknown small structure in common such as a Ribozymic activity produces. ...
in the future, technology such as microscopic 3d printing may help solve the problem.
