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These organisms perform photosynthesis through organelles called chloroplasts and are believed to have originated about 2 billion years ago. [1] Comparing the genes of chloroplast and cyanobacteria strongly suggests that chloroplasts evolved as a result of endosymbiosis with cyanobacteria that gradually lost the genes required to be free-living.
Chloroplasts, containing thylakoids, visible in the cells of Ptychostomum capillare, a type of moss. A chloroplast (/ ˈ k l ɔːr ə ˌ p l æ s t,-p l ɑː s t /) [1] [2] is a type of organelle known as a plastid that conducts photosynthesis mostly in plant and algal cells.
Chloroplasts have their own genome, which encodes a number of thylakoid proteins. However, during the course of plastid evolution from their cyanobacterial endosymbiotic ancestors, extensive gene transfer from the chloroplast genome to the cell nucleus took place. This results in the four major thylakoid protein complexes being encoded in part ...
An even closer form of symbiosis may explain the origin of chloroplasts. Chloroplasts have many similarities with photosynthetic bacteria, including a circular chromosome, prokaryotic-type ribosome, and similar proteins in the photosynthetic reaction center.
Like mitochondria, chloroplasts have a double-membrane envelope, called the chloroplast envelope, but unlike mitochondria, chloroplasts also have internal membrane structures called thylakoids. Furthermore, one or two additional membranes may enclose chloroplasts in organisms that underwent secondary endosymbiosis , such as the euglenids and ...
An overview of the endosymbiosis theory of eukaryote origin (symbiogenesis). Symbiogenesis theory holds that eukaryotes evolved via absorbing prokaryotes. Typically, one organism envelopes a bacterium and the two evolve a mutualistic relationship. The absorbed bacteria (the endosymbiont) eventually lives exclusively within the host cells.
The chloroplasts of red algae have chlorophylls a and c (often), and phycobilins, while those of green algae have chloroplasts with chlorophyll a and b without phycobilins. Land plants are pigmented similarly to green algae and probably developed from them, thus the Chlorophyta is a sister taxon to the plants; sometimes the Chlorophyta, the ...
Chloroplasts probably evolved following an endosymbiotic event between an ancestral, photosynthetic cyanobacterium and an early eukaryotic phagotroph. [17] This event (termed primary endosymbiosis) is at the origin of the red and green algae (including the land plants or Embryophytes which emerged within them) and the glaucophytes, which together make up the oldest evolutionary lineages of ...