Zellorganellen - Die Endosymbiontentheorie

Summary

Key Points

• The Endosymbiotic Theory describes how simple single-celled organisms evolved into complex plant and animal cells with nuclei and organelles. 0:33
• The process began when a larger archaebacterium engulfed a smaller alphaproteobacterium, potentially for a hydrogen supply, leading to the smaller organism gaining a second membrane. 1:22
• Over millions of years, the absorbed alphaproteobacterium lost its self-sufficiency, with many of its genes either lost or transferred to the host cell's genetic material. 1:41
• This engulfed bacterium evolved into a mitochondrion, an organelle that became highly efficient at producing the energy source ATP for the host cell. 2:15
• Subsequently, the host cell formed a cell nucleus and then absorbed a cyanobacterium, which possessed the ability to photosynthesize. 2:27
• The absorbed cyanobacterium evolved into a chloroplast, providing the host cell with the crucial advantage of converting sunlight and water into oxygen and sugar. 2:43
• Similar to mitochondria, chloroplasts also lost a significant portion of their genomes, transferring over 95% of their genes to the cell nucleus. 3:20
• Strong evidence for the endosymbiotic theory includes the double membrane of mitochondria and chloroplasts, their own ring-shaped DNA, their replication by division like bacteria, and the presence of bacterial genes in eukaryotic nuclei. 4:00
• Endosymbiosis is a recurring evolutionary strategy, demonstrated by various organisms such as single-celled algae and the sea slug Elysia chlorotica, which utilizes absorbed chloroplasts for photosynthesis. 4:19