Herbivory Flashcards
What is herbivory?
The consumption of whole plants (primary producers) or plant material, by animals known as primary consumers.
What is the total global biomass?
550 billion tonnes.
Why are plants not always the most nutritive food?
Plants have low nitrogen content and herbivores have to eat a lot of it and be efficient at digesting.
What are some adaptations that are required for herbivores to digest plants?
The right shape and size for best access to the plants, strong jaws and durable teeth and a large rumen to digest cellulose using symbiotic micro-organisms.
What is the difference between specialist and generalist herbivores?
Specialists feed on one type of plants whereas generalists can feed on multiple types of plant.
What impact do herbivores have on plant populations?
They can reduce plant growth rate and reduce plant reproductive output
How can herbivores reduce plant reproductive output?
They can directly reduce it as seed predators or indirectly reduce it by reducing plant biomass.
What is an example of herbivorous insects that can defoliate forests?
The spruce budworm.
What is an example of an area that was affected by cattle grazing?
Mauna Loa Volcano, Hawaii.
In what ways can herbivores affect diversity?
Herbivores that prefer dominant plants can increase diversity whereas herbivores that prefer subordinate plants can decrease diversity.
How do herbivores impact the ecosystem?
They produce a large amount of CO2.
What are some of the positive effects herbivores might have?
They can induce plant growth and be valuable controllers of invasive plants.
What is an invasive species?
A species new to an area where it grows unchecked - lack of competitors or/and parasites or/and herbivores.
What is an example of an invasive species?
The prickly pear cactus and cactus moth. The cactus moth controlled the prickly pear when it was introduced to Australia.
What is another example of an invasive species in California?
The Klamath weed that was controlled by a leaf beetle.
How can invasive species be brought under control?
A specialised herbivore.
Why have all the plants in the world not been eaten already?
They have mechanical defences such as leaf toughness, spined leadf margins, thorns, spines and are covered by wax.
What are some of the phenological defenses plants have?
Producing an excess of seeds (mast fruiting) so the predators become full before eating all of the seeds.
What are some of the hormonal defences plants have?
Reproductive inhibition to prevent some insect herbivores from developing.
What are some of the biochemical defenses plants have?
Secondary chemicals (not needed for development) such as THC in marijuana, mustards and tobacco that are nitrogenous secondary compounds to deter predators.
Why do plants produce a combination of several chemical defenses?
Synergism (producing a greater effect) and there are many herbivores.
What are constitutive defenses?
They are expressed at all times.
What are induced defenses?
The expression is increased (or turned on) after attack.
Are detrivores classed as herbivores?
No
Example of how herbivores increase plant growth?
Clipping can induce fruit production - field gentians Gentianella campestris.
What is the genetic basis of plant defence against herbivores?
Herbivores eat plants lacking defence genes - when a defense gene was silenced, 92% of the plants were attacked by herbivores.
What is the problem with producing multiple defence chemicals?
It may be expensive.
Why might plants have induced defences instead of constitutive defences?
The cost of defence is too high to maintain under light herbivory.
