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4 Cards in this Set

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Describe cases of spatial patchiness which could limit herbivores’ ability to consume plants.
Spatial patchiness of plants may protect them from herbivory. For example, New Hampshire USA, the plants on cliffs are patchy. It could be costly for herbivores to find enough of any one plant type to survive here.
Explain how short-term (phenological) and long-term (successional) temporal variation in plant availability could act to control the impact of herbivores on vegetation.
Plant resources can also be temporally patchy - This makes enough of the suitable plant material hard to find. For example, fruit trees act seasonally.

-Short term: At different seasons, there are very different affordances for herbivores attacking apple trees for example.

-Long Term (Successional): At longer timescales, vegetation types replace each other at a site, and adjacent patches of the habitat may be at very different stages in the process because disturbances are also patchy in time and space.
Use instances of abiotic disturbances (e.g. fire) and stochastic variation in conditions (e.g. mast and non-mast years) to explain further limitations on herbivory.
Abiotic disturbances can effect herbivore consumption habits.

-Fires, at the end of a hot dry summer, can cause habitat fragmentation. This is likely to remove a lot of food from the ecosystem. This comes at a time when herbivore populations are large (at the end of summer) and plant quality is declining. If you are a generalist, you can switch diet. For Gouldian finches, that lose seeds during fires, they move unpredictably from patch to patch as each is burned. If you are less mobile, you will be more effected by these fires.

-Variation in growing seasons can effect herbivores as well. Hot summers result in good fruit production that can increase populations of herbivores. For example, the population of voles in Northern Europe that carry disease increase after hot summers and good fruit production years. Consequently, disease spikes up.
Describe and explain how herbivore digestive morphology, physiology, and mutualistic associations permit specialized cases of improved feeding efficiency.
-The digestibility of plant tissue can be difficult for herbivores since most plant sugar production goes to the structural material cellulose. Cellulose is bonded in such a way that it cannot be easily broken down. Therefore, plants offer only a small proportion of useful nutrients.

-Hindgut fermenters: rely on bacteria in the caecum and colon to liberate nutrients from plant material
-Because hindgut fermenters are less energy efficient, they have to seek out higher quality foods and experience more competition.
-Hindgut fermenters have gradually lost biodiversity due to its inefficiency.

-Ruminant Mammals - Have an extra set of fermenting organisms in the foregut which releases energy rich fatty acids for absorption. They also chew more and have some hindgut fermentation.
-The higher efficiency of ruminants have allowed them to dominate small mammal leaf eating niches (larger species can gain enough efficiency just from size not digestive tract specialization).