endosymbiosis Flashcards
What is symbiosis?
It’s when two organisms live together closely, often benefiting each other.
What is endosymbiosis?
When one organism (the endosymbiont) lives inside another organism (the host), often in a mutualistic relationship.
How does endosymbiosis occur?
The endosymbiont enters the host cell by endocytosis, where the host’s membrane pinches off to create a vesicle.
How did endosymbiosis contribute to the evolution of eukaryotic cells?
Mitochondria were once free-living prokaryotes. Larger, anaerobic prokaryotes took them in for better energy production through aerobic respiration.
Why was the endosymbiosis relationship beneficial for both organisms?
The host received more energy from the endosymbiont’s aerobic respiration, and the endosymbiont received food from the host.
What did natural selection favor in endosymbiosis?
Natural selection favored the relationship because it was mutually beneficial, and the endosymbionts could divide and persist as long as they kept up with the host’s growth.
How did the endosymbionts evolve over time?
Over millions of years, the endosymbionts evolved into mitochondria, becoming a permanent part of eukaryotic cells.
How does the endosymbiotic theory explain the origin of chloroplasts?
The theory suggests that a photosynthetic prokaryote was engulfed by a host cell and evolved into a chloroplast.
Why is the endosymbiotic theory for the origin of mitochondria and chloroplasts still considered a theory?
It cannot be conclusively proven, but there is strong evidence supporting it.
What are some features of mitochondria and chloroplasts that support the endosymbiotic theory? (5)
- Double membrane – suggests the engulfment of a single-membrane organism.
- Own genes – circular DNA, like prokaryotes.
- Protein synthesis – they transcribe their own DNA and make their own proteins.
- 70s ribosomes – similar to prokaryotic ribosomes.
- Reproduction – they can only divide to form new ones, just like prokaryotes.
