2 - Symbiosis Introduction Flashcards
(22 cards)
What is symbiosis
A close, long-term interaction between different species where at least one benefits
It involves a host and a symbiont, and includes mutualism, parasitism, and commensalism
In which domains of life does symbiosis occur
Across all domains:
Plant–fungus: Mycorrhizae
Animal–microbe: Mammalian gut flora
Animal–algae: Coral and zooxanthellae
What is vertical transmission in symbiosis
Symbionts are passed from parent to offspring
Example: Buchnera bacteria in aphids
What is horizontal transmission in symbiosis
Symbionts are acquired from the environment each generation
Example: Coral–algae symbiosis
What is obligate symbiosis
A symbiotic relationship required for survival or function
Example: Termites and their gut protists
What is facultative symbiosis
A symbiotic relationship that is not essential but beneficial
Example: Rhizobia in legumes
How do mycorrhizal fungi support plants
They enhance mineral (P, N) absorption via hyphae
Case study: “Wood wide web” – fungal networks connecting trees
What is photosynthate transfer in symbiosis
Algal symbionts provide sugars from photosynthesis.
Case study: Zooxanthellae in reef-building corals
How do symbionts aid digestion in ruminants
Gut microbes break down cellulose into fatty acids
How do termites digest lignin
Protist symbionts in their guts break down lignin
What do Buchnera bacteria provide to aphids
Essential amino acids that aphids can’t synthesise
What symbiont produces antibiotics for beewolves
Streptomyces bacteria – protect wasp larvae from pathogens
How does Hamiltonella benefit aphids
Defends them from parasitic wasps
What does Spiroplasma do for fruit flies
Kills nematodes and worms that parasitise the flies
How does Wolbachia provide viral immunity
Reduces viral loads in Drosophila
How do Photorhabdus bacteria kill host insects
They kill insect hosts to feed both the bacteria and their nematode hosts – used as a form of offensive symbiosis
How is symbiosis relevant to coral reef conservation
Coral bleaching results from breakdown of coral–algae symbiosis. Understanding this aids reef management and restoration
Why is the human gut microbiome important
It’s crucial for digestion, immune function, and neurological health
What is a faecal transplant used for
To treat antibiotic-resistant infections like Clostridioides difficile by restoring a healthy gut microbiome
How do mycorrhizal fungi help in agriculture
They increase nutrient uptake, reducing the need for fertiliser
What is the role of rhizobia in legumes
Nitrogen fixation, improving soil fertility naturally
How are microbial pesticides used
Defensive microbes are used to control crop diseases and insect pests, reducing the need for chemical pesticides
