Herbivory Flashcards
What is herbivory?
The consumption of whole plants (primary producers) or plant material by animals (primary consumers)
Why are herbivores a ‘critical link’?
All energy enters biotic community via plants
Why aren’t all animals herbivores?
Plants aren’t always the most nutritious food
- low N content
What special adaptations can herbivores have to digest plants?
Strong jaws/bill
Durable teeth
Large flat teeth for grinding
Large rumen to digest cellulose using symbiotic microbes
What are the 2 ‘flavours’ of herbivores?
Specialist e.g. koalas & eucalyptus
Generalists e.g. deer, cows
When can being a specialist herbivore be a problem?
If food source becomes scarce
How much impact do herbivores have on plant populations?
Reduce plant:
> growth rate
> reproductive output
How can herbivores reduce plant reproductive output?
Directly as seed predators
Indirectly by reducing plant biomass
What effects do herbivores have on biodiversity?
Herbivores that prefer dominant plants –> increase diversity
Those that prefer subordinate plants –> decrease diversity
What positive affect can herbivores have?
Induce plant growth
–> cut main apical meristem = releases secondary side meristems
What is an invasive species?
A species new to an area where it grows unchecked
How was the Prickly pear cactus controlled in Australia?
Cactus moth from S. America was v specialised and ate all prickly pears
Why don’t herbivores eat more of the terrestrial plant biomass?
Plants have defences
More food in ecosystem increases predator population size
What are the mechanical defences that plants have?
Leaf toughness
Spined leaf margins
Thorns
Wax
What is a phenological defence?
When all plants in an area mask fruiting so that seed predators die
Flower few yrs later
What is the hormonal plant defence?
Produce chemicals that mimic insect hormones
–> inhibit metamorphosis of insect herbivores
What is the biochemical plant defence?
Chemical plant compounds - secondary chemicals
not necessary for plant development
Give examples of secondary compounds used against herbivores
THC in marijuana = alkaloid
Tobacco contains nicotine = alkaloid
Why do plants produce a combination of several chemical defences?
Synergism
Many herbivores
What are the 2 types of defence in terms of when they’re expressed?
Constitutive = expressed at all times
Induced = expression increased under attack
