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Chapter 26: Community Ecology (Predator-Prey Interactions Link Title (One…
Chapter 26: Community Ecology
Concepts
Community: a group is species that occur together at the same time and place
Population biology: focuses on the members of a single species, their growth, interbreeding, survival, etc.
A community can be a forest or an ocean, but it an also be a region of same communities. For example, organisms living along streams and rivers, or an organisms that live on tree branches, or even organisms that invade the body of a plant or animal after it has died.
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Community ecology might examine the same species, not taking into consideration its interaction with other species
Diversity
diverse communities consist of different variety of factors: including animals, plants and sometimes habitats
Scale matters in community diversity; the larger to area the more diverse
The relationship between area and space richness is called
species-area relationship
and it is expressed by the formula S=cAz
S is the number of species, A is the area, c and z are constants that must be discovered by studying individual communities
once c and z are known for various communities, they can be used to compare the diversity of those communities
Predator-Prey Interactions
Link Title
One Predator, One Prey (helps us understand, as humans how we should harvest our various prey)
example: a primary producer is attacked by a primary consumer
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Functional Response: Two fundamental aspects together: which are the predators feeding rate and its handling time
Feeding rate refers to how quickly a predator find a new prey individual, and handling time refers to the amount of time needed to actually consume the prey
feeding rate will be faster if there are more prey individuals available, so a predator's functional response is dependent on pray density, it is prey-dependent
Lotka-Volterra model
Link Title
it models the net rate of change in prey numbers as dN/dt = rN-aNP; the equation for the net rate of change of predator numbers is dP/dt = faNP-qP; The population of prey will be stable when dN/dt=0; The prey population is stable when the density of the predator equals r/a, the pop of predators is stable when dP/dt=0.
Zero growth isocline; the line that indicates population stability. It illustrates the effect of prey density of predator population
More graph models in book pgs: 714-716
Predator selection among prey
in many cases, a predator consuming or laying eggs of just one species and ignoring all others
Three factors that are initially important in a predator's choice of prey include: the probability that a prey individual will be encountered, rare species will be consumed less than abundant ones, and those that are cryptic due to the coloration or smaller size may escape detection
Competition: exploitation, is a resource competition that occurs when the organism actually consumes a shared resource making it less available for other organisms; interference when one organism restricts the other organisms access to resources even though the first might not be using it
apparent, an increase in one plant species associated with a decrease in others, and they appear to be in competition, the plants aren't actually competing for and using a resource
Meta-populations and Interconnections of Species
Meta-Populations: several local populations are interconnected through migration and gene flow between the patches
Interconnectedness of Species
food chain: choosing one predator then identifying its main prey and the plant species
food web: tracing all prey of the top carnivores and then tracing the food sources of each of those prey species and so on, we obtains a network of numerous interrelations
energy flow web: various organisms eat or decompose others, and this is turned and consumed. Because some organisms consume the same prey, and in turn each is consumed by various other organisms, energy flows through the community in a web-like pattern
Keystone species: a species that dramatically effects the structure of its community, having an impact out of proportion to its size or the number of individuals present
