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Community Ecology (Concepts (Community (species that occur together (at…
Community Ecology
Concepts
Community
species that occur together
at same time
same place
examine many species intereactions
other species might be in competition
or might be predator
many other relations
mutalistic
commensalism
boundaries in time and place
#
forest - an example
some factors prevents tree from growing too big
tree lines
regions too wet for tree to gorw
smaller communities within
organisms that live in lakes
communities that in live tree's branches
smaller communities make up large communities
Boundaries in time
#
come into being and cease to exist
beavers build a dam and over time stream build
Succession
predictable sequence of changes over time
in an area
some remain same for many years
typically results in climax community
community ecology
important
organisms affect one another
know what impacts what
Community restoration
work and projects
back to original
Diversity
communities - more than one species
some more diverse than others
species richness
count of species present
species checklist
always incomplete
impossible
usually not necessary
all national parks and wildlife
Diversity and Scale
scale
common observation matters
larger areas-more diverse
more variations
in types of soil
topography
geology
larger population
less likely to die out
species-area relationship
S = cA^z
S - # of species
A - area
c & z - constants
study individual communities
species abundance distribution
Diversity and Latitude
diversity varies with latitude
oldest theory
tropical regions
near equator
benign environments
higher latitude
more severe conditions
Beneficial Interactions between Species
both organisms benefit
mutualism
mutualistic relationship
example:
pollinators and the plants they pollinate
natural selection favors mutations
that reduce costs and minimize benefits
one helps another w/o any benefit
#
facilitation
plays role in succession
primary succession especially
new created substrates
animals become established
1st organism facilitates presence of the other
example
beavers
they build dams thats useful to environment
not useful to them though
Mutualism is not free
flowers either produce nectar or lose pollen
minimizing cost
myorrhizal associations
symbioses between root nodules
Interconnectedness of Species: Food Chains and Food Webs
simplest communities
at least 3 trophic levels
primary consumers
herbivores
secondary consumers
carnivores
primary producers
plants,algae,cyanobacteria
harsh condition environment
primary producers pop in sparse
herbivores sparse
very few carnivores
so only 3 levels
in better areas
can be more
carnivores feed on carnvores
higher levels
food chain
#
set of organisms
all three levels
direct line of comsumption
food web
network of numerous interrelationships
energy food web
keystone species
drastically affects the structure
dominant species will have a strong impact
easy to recognize if removed/restored
diff. to recognized on food web :warning:
Predator- Prey Interactions
One Predator, One Prey :red_flag:
primary producer
attacked by primary consumer
natural communities
plant is attacked by multiple predators
almost every herbivore attacks
several species of plants
important
more species present
competition + growth slow
two fundamental aspects
predator's feeding rate
how quickly
its handling time
amount of time needed
the two make up
predator's functional response
dependent on prey density
Lotka - Volterra model
dN/dt = rN -aNP
criticized
too simplistic
Zero growth isocline
Competition Between Species :red_flag:
often compete for same resources
interspecies competition
one plant competes with other plants
water
light
minearls
exploitation competition
organisms consume shared resource
interference competition
one organism restricts resource
Apparent Competition :red_flag:
prey species share predator
prey pop. low, predator pop. low
vice versa
plants not competing/using resource
Metapopulations in Patchy Environment
world - patchy and heterogeneous
many areas suitable for one species
physically and geographically separated
ex. Maples
metapopulation
several local pop.
interconnected by migration
gene flow between patches
4 assumptions
discrete patches
sink habitat
low quality
source habitat
high quality
some patches occupied some not
pop. size always vary
conservation/perservation
empty patch - become colonized
ex. birds flying from one to another
migration important
pop. in patch have probability of going extinct
fugitive species
