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Chapter 26 : Community Ecology (Beneficial Interactions Between Species…
Chapter 26 : Community Ecology
Concept
community
group of species occur together at same time/place
succession
more or less predictable sequence of change
climax community
undergoes succession until it becomes spruce-fir forest
stability returns
community restoration
reintroducing wolves into Yellowstone National park
encouraging the migration of bears
mountain lions across the Rio Grande River from Mexico into Big Bend National Park in Texas
habitat loss and habitat fragmentation
even though we are trying to live more harmoniously with nature
still need to farm
build towns
mine for minerals
Diversity
Diversity and Scale
scale
common observation
species-area relationship
relationship between area
species richness
S=cA^z
species abundance distribution
plot the number of species in each abundance class
Diversity and Latitude
diversity with scale
varies with latitude
ecological explanation
satisfying
not the entire explanation
checklist
first approach to quantifying community diversity is done by measuring species richness
simply a count of the species present
all national parks and wildlife preserves have
Predator-Prey Interactions
One Predator, One Prey
functional response
handling time refers to the amount of time needed to actually consume the prey
feeding rate refers to hoe quickly a predator find a new prey individual
prey-dependent
feeding rate will be faster if there are more prey individuals available
predator's functional response is dependent on prey density
zero growth isocline
line indicating population stability
paradox of enrichment
might important factor in the loss of species diversity when a habitat is "improved"
maximum sustained yield
harvest just enough of species to keep the population density
species would be stable
would obtain
fixed effort harvesting
population health is determined by amount of fish or deer
fixed quota harvesting
fisherman or hunters are allowed to harvest a particular amount
such as
one deer per hunter
certain number of tons of fish per fleet
no matter how long it takes or how much effort is required
Predator Selection Among Multiple Prey
optimal foraging theory
examine the interactions between these factors in an attempt to understand why herbivores eat the plants do while ignoring others.
optimal diet model
optimal foraging theory has produced
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make four predictions
Apparent Competition
plant are not actually competing for and using a resource
plants often face the problem that many herbivores will eat plant
Competition Between Species
exploitation competition
resource competition occurs wen the organisms actually consume a shared resource
making it less available for other organisms
interference competition
one organism restricts another organism's access to resources even though the first might not
example
bracken ferns produce large leaves up to 3m long that emerge from a subterranean rhizome one petioles as must as 1m tall
invasive
species increase from very low population density with competitor present
resource
substance or factor that can lead to increased growth rates as it increased
consumed by an organism
Metapopulations in Patchy Environments
source habitat
high-quality patch
sink habitat
low quality one
common model of metapopulations
region environment is composed of many discrete patches in species can live
some patches are occupied by the species whereas other suitable patches are not
empty patches will become colonized by migration from occupied patches
population within individual patches have a probability of going extinct within that patch
fugitive species
survives by colonizing new patches, flourishing temporarily
colonizing more patches before it diet out in old ones
assisted dispersal
called assisted migration
animals are captured in one area
released into the new area
Interconnectedness of Species: Food Chains and Food Webs
food chain
simplest is choose one predator
identify mai prey
plant species that supports them
food web
trace all the prey of the top carnivores
trace the food sources of each of those prey species
network of numerous interrelation ships
energy flow web
extremely difficult to construct energy flow webs for real communities
keystone species
presence or absence of certain species
Beneficial Interactions Between Species
mutualism relationship
various organism within a
community often interact in way are beneficial
two organisms interact such that both benefit
facilitation
one organism helps another without receiving any benefit
facilitates
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first organism the presence of the other
nurse plants
small area of habitat immediately below themselves
more favorable to the survival of seedling of other plants as compared other nearby not below
primary succession
facilitation plays a role in succession
organisms become established on newly created substrates
