Lecture 23: Trophic Relationships and Plant-Animal Interactions Flashcards
primary producers
plants
primary consumers
herbivores
secondary consumers
predators (carnivores who eat herbivores)
tertiary consumers
predators who eat other predators (sec. consumers)
decomposers
eat dead organic matter and return nutrients to external environment
Why is there more biomass in lower trophic levels
inefficient transfer of energy
food chain and food webs
drastic oversimplifications, only shows trophic interactions (where one animal eats the other) and not other interactions like gamete dispersal
Various names for plants
- primary producers
- autotrophs
trophic interactions are…
direct effects
indirect effect
one species alters the effect that another species has on a third
trophic cascades
interactions between two trophic levels cascade to a third trophic level
ex. carnivores eating herbivores reduces amount of herbivory thus helping plants.
HSS Green world hypothesis
top down control
What’s stronger, indirect or direct benefits?
Trick question, indirect benefits can be as strong as direct but it depends on the interaction strengths
Difficulties associated with herbivory
- plant tissue hard to break down (indigestible without microbial symbionts)
- plant tissues heavily defended against herbivores
Why are there so many species of plants???
Coevolutionary arms race between plants and insect herbivores responsible for much of biodiversity (specialization is common)
secondary compounds deter… but not…
- generalist herbivores
- specialist herbivores
Specialist insects may use defense chemicals as…
feeding stimulants or defense compounds
Challenges and solutions for vertebrate herbivores
- eat varied diet of plants to avoid high doses of any one toxin
- some detoxification is done by microbes in fermenting chambers
Janzen-Connell Hypothesis
Insect-plant coevolution might explain how biodiversity of tropical rainforests evolved but doesn’t really explain how it is maintained.
- seedlings have low chance of success in vicinity of mother plant (high chance of being attacked by same herbivorous organisms but no defence because they’re a baby)
- strong density-dependence prevents any one species from monopolizing habitat
