Herbivory (pre)

Question 1

Why is the world still green even with so many herbivores?

Answer 1

Herbivores get eaten​
Plants are Cruddy​
Plants are defended​

Energy loss between trophic levels may limit consumption (Bottom-up control)​
The Hubbard Brook study highlights energy loss in ecosystems​
Only 0.01% of solar energy is assimilated by herbivores!​
Trophic control is a powerful mediator of plant-animal interaction.

Question 2

Plants are cruddy!

Answer 2

Comprised of hard to digest materials​
Low water content​
Low amounts of N, P, C and much is unusable to herbivores ​

Question 3

Plant defences

Answer 3

physical
chemical
biological

Question 4

Predator-prey population cycles​

Answer 4

Any increase in hares is quickly matched by an increase in lynx populations​

Question 5

Trophic cascades -Yellowstone Wolves​

Answer 5

Wolves were hunted to extinction in Yellowstone National Park in the 1920’s​
The loss of the top predator resulted in increased herbivore (Elk) pressure on native trees (Aspen) and significant changes in habitat quality​

Question 6

What factor affects plant community

Answer 6

Trophic control of plant-herbivore interactions is an important factor affecting the plant community (Trophic Cascades)​ Underscores the impact of herbivory on plants and why their ecophysiology is so influenced by herbivore attack ​

Question 7

rabbits and grass

Answer 7

Rabbit exclusion (1908) resulted in dominance by a handful of grasses​
Where rabbits remained, more plant species were present

this is because When rabbits are excluded from an area, certain grass species may experience reduced grazing pressure, allowing them to proliferate and dominate the vegetation. These dominant grasses may outcompete other plant species for resources, leading to a less diverse plant community.
On the other hand, in areas where rabbits are present, their grazing behavior may prevent the overgrowth of certain grass species. The presence of rabbits can create a more balanced ecosystem by controlling the abundance of dominant grasses and allowing a greater variety of plant species to coexist.
​

Question 8

Herbivore control of species diversity​

Answer 8

Exploiter mediated coexistence - predation promotes the coexistence of species where there would otherwise be competitive exclusion ​

Question 9

Selective herbivory on seedlings​

Answer 9

Herbivory during the regeneration stage has greatest effects on plant mortality and seedling predation can be especially selective​

Question 10

Importance of seedling herbivory​

Answer 10

Plots sown with seeds of six common grassland species in September 1993 ​

Question 11

intermediate disturbance hypothesis

Answer 11

The intermediate disturbance hypothesis suggests that local species diversity is maximized when ecological disturbance is neither too rare nor too frequent. At low levels of disturbance, more competitive organisms will push subordinate species to extinction and dominate the ecosystem.
Ends up looking like a hump on a graph