Three general catagories of hunting tactics
ambush, stalking, pursuit
lie and wait; requires minimal energy; low frequency of success
deliberate tracking of prey; quick attack, most time spent encountering prey
minimal search time; pursuit time great
Predator avoidance; prey strategies
variety of defferrent stratigies; suggest predation is a stron selective force;

ex: moth ears have evolbved in responce to bat echolocation

Aposematic coloration (warning)
color pattern advertises distasteful or poisonous nature; black and yellow, brightly colored, orange
camouflage; zebras look like broken grassland, bay pipefish look like eel grass
frozen posture; movement alerts predator
mimic other undesirable organisms

Mullerian (unpalatable species look alike)

Batesian(palatable species mimics unpalatable species)

startle or scare off predator; toad swallows air to look larger, frilled lizard makes it look bigger, eyespots on moths
Chemical defense
use of chemical irritant

skunks, octopus, bombarder beetle sprays noxious chemicals

synchronous reproduction; saturate predators

Cicadas (13 or 17 year cycles) white oak trees

Consumers can limit resource populations
sea urchins exert strong control on algae populations… if removed biomass of algae increase and the whole community shifts
Things that make an effective preditor
high reproductivity relative to prey, excellent dispersal powers, can switch to alternative food source; keystone predatror
Type 1 Predator consumption rate vs. prey density
consumption proportonal to density;
Type 2 predator consumption rate vs prey density
consumption increases rapidly then plateaus; the most common type;
Type 3 predator consumption rate vs. prey density
like type 2 but prey consumption depressed at low prey density; heterogeneous habitat provides hiding places; predator switching to alternative food source
Predator prey regulation
functional responce alone is not adequate for regulation; predators consume more and more prey only to the point of satiation; more predators required
Numerical responce
change in predator population size in responce to prey density (more births or immigration/ aggregative)

Total responce = Functional responce x Numeric responce

The three level consumer system takes into account
food supply, prey density and predators
Population cycles are produced by
delays in responce of births and deaths; time required to produce offspring; population cycles tend to be 4-5 times the length of the lag time
Lag time in Pathogen host system
immune responce create infection cycles; measles epedic- 2 year cycle prior to vaccine this was the time required for a new population of susceptible infants to accumulate.
Stability of prey predator system
1. predator inefficiency
2. alternative prey
3. partial refuges
4. small lag time
Exotic preditors
destabilize natural systems because they lack the coevolutionary responcses of native predator prey systems
example of Trophic mutualism
exchange of nutrients and energy the ungulate in the stomache of herbibores
example of Dispersive mutalism
food in return for moving propagules or pollen
example of Defensive mutualism
food or shelter in return for defense
Two parties have a Facultative mutualistic partnership if
partners can live without one another
Two parties have a Obligate realationship if
partners cannot exist without eachother
an example of Dispersive mutualism
pollinators and flowers
an example of Defensive mutualism
cleaner wrasse for larger fish
an example of Defensive mutualism
shrimp goby deffending burrow
group of population sof different species that occur together in place and time
Communities can be defined
major species, groth habitat, geographic location, climate type, taxon, or tropic level
Community descriptions include
biodiversity, response to distrubance, tropic structure (feeding relationships)
Disturbance in a community
prominent feature of most communities; stormes fires, floods, droughts and human activites

damage bilogical communities, remove organisms, alter the avalability of resources

Closed community
close association between species reglates distribution of whole community
Open community
species are distributed independently ot one another, regulated by environmental conditions
where species and environmental gradients overlap
Closed communities
clements where species overlap, ecotones
Open community
Gleason (open) the evnironmental gradient of species do not over latp with other species
In a closed community
1. Organization holistic
2. Boundries distinct
3. Species ranges coincident
4. Coevolution: prominent
Open community
1. Organization; individualistic
2. Boundries: diffuse
3. Species ranges indipendent
4. Coevolution: uncommon
Closed community concept
sharp boundris between communities; terrestrial and aquatic; soil type (edaphic), exposures (N or S); dominat life forms
Open community concept
most species have distributions outside of their ecological optima; most accepted view in ecology
sharp physical change examples are soil properties, land to equatic environment
Continuum concept
different communities re;lace each other gradually over broad environmental gradients

ex: galacier retreat caused organisms to move notry;

Physical structure of communities
Vertical: layers depth or bilogical example is trees create a canopy, underneith are different height of plants shrubs etc

Horizontal: Patchiness, and physical example march land, grass land, shrubs, and trees

Biotic structure of communities
guilds, dominants, complexity, diversity
Dominants in a community
one or a few species are predominate; highes biomass in an ecosystem, largest contribution to energy or nutrient flow, keeystone species
Community complexity
the amount of tropic levels in a food chain; energy supply limits the length because each tropic level 10% of the energy is converted to biomass
Community diversity
food chain lenght limits community diversity
Important components of stability
resistance: ability to survive disturbance unchanged

Resilience-ability to reconver from a disturbance to original state

The capacity for an ecosystem to return to its former state following a disturbance
Factors that affect community diverstity and structure
long term historcial effects, disturbance, competition, predation, mutualism productivity of climate, dispersal of organisms and extinction
What is a long term historical effect?
The island of pangae, or the ice bridges during the ice age
Non equilibrium communites; species diversity is dynamic; community structure determied by disturbance;
Community disturbance
Prevents dominance, increases horizontal structure; increases or decreases diversity
The intermediate disturbance hypothesis
Intermediate levels of distubance promote higher level of diversityhigh levels reduce; low levels allow competition and reduce diversity
Diversity is determined by the number of available niches
this is the traditional view; nember of species does not fluctuate from equilibrium; determined by predation and competition; new species can invade only after the similar speices leaves or goes extinct
Competition occures within
trophic levels or guilds
Niche differentiation and character displacement
Effect on target is positive

effect on competitor is none

effet on community diversity; can remane equil, or be positive

Increase resource use efficience has what effect on community?
effect on target is positive, effect on competitior is zero and effecto on community diversity, remains constant
Increase in resource uptake in communities
posive effecte on target; negative effect on competitor and negative effect on community diversity
Tropic cascade
indirect interactions impact the community characteristics
Bottom up control
increased production increases productivity at all tropic levels
Top down control
consumers depress prey and indirectly increase the next lower tropic level
Stability/ time hypothesis
stable climates = higher diversity ex: around equator
Species richness energy model
more energy or productivity more species can coexist
Energy from the sun is a ccumulated in plants and that energy can go 2 ways
The living biomass can be consumed ; herbivore based, mostly in aquatic ecosystems(60-90%) in plankton communityies….Or Dead biomass can be consumed (detritivore based) predominent in terrestrial ecostystems
ability to sustain a disturbance unchanged
Sereal stages
each step in succession
the total succession of all plants in an area
Degradative succession
the succession of fungi bacteria, invertebrates, vertebratesw and plants.. the returning of nutrients back to the earth
Mechanism of succession
facilitation, inihibion, tolerance
each stage changes environment to help the next stage; often through soil improvment

ex: organic litter, N2 fixing species etc..

one species prevents others from inhabiting… determined by what arrives first,
depends on ability to tolerate physicla conditions, temp drought etc
Facilitation, inhibition and tolerance work together
pioneer species facilitate net stage, inhibition new species replace pioneer, the new must be tolerant in order to survive
Tropical forest diversity is organized in 2 ways
large number os species live within the community and there are large number of plant community in the given area
Increasing nutrient availability and environmental complexity
reduces number of limiting nutrients, leaving the only thing left to compete for is light and those competeting for light will dominate the community
Energy goes to two pathways
living biomass comusmed or dead biomass consumed
Herbivore based
consumption of living biomass is domenant in aquatic ecosystems
Herbivore based
consumption of living biomass is domenant in aquatic ecosystems
Detritibvore based
dead biomass is consumed and is predominate in terrestrial ecosystems
Gross primary production
total energy assimilated by primary producers
Net primary produciton (NPP)
energy accumulated in biomass of primary producers

NPP= gross produciton – respiration

Highest Net Primary productivity
tropical latitiudes
Lowest NPP
Desert and artic
Intermediate NPP
temperate forest and grassland
Ocean NPP
Higest at continental edges and shallow water, lowest in opean ocean
Large portion of the globe is low productivity
30% land and 90% of the ocean
Factors that influence primary production
water, temperature, length of growning season, nutrients
Nitrogen is a limiting nutrient in
terrestrial environments and open oceans
Phosphorous is a limitng nutrient in
freshwater environments
Compensatory growth
lower rates of respiration due to lower plant biomass, reduced self shading and improved water balance due to reduced leaf area, the grazing increased the growth rate of many grass species
Assimilatory process
biochemical tranformation of inorganic nutrients into organic form through photsynthesis
Dissimilatory process
tranformation of organic form to an inorganic nutrient via respiration
Gaseous reservoirs
primary nutrient resivori is the ocean and atmosphere
global cycles
Sedimentary reservoirs
primary nutrient reservoir like earths crust; more local
Global carbon cycle
all organic molecues; a function of photosynthesis and respieration
Carbon cycle
sum atmosphere, photosynthes, land, repiration and decomposition, deforestation fossil fuel atmosphere to the ocean, sedimentation
Global nitrogen cycle
atmaosphere huge pool of N2 not usable by plants, biological fixation requireed
the conversion of amino acids to NH4
the oxidation of ammonimum into NO3
Nitrogen fixation
chemcial tranform of N2 to NH4
the reduction of NO3 to N2 ore molecular nitrogen
Atmospheric Nitrogen fixation
lightning breaks the N2 and enables atoms to combine with oxygen forming NO2 and NO3 these disolve in rain and are carried to the earth
Cyanobacteria and fee living soil microorganisms fix N
this is 90 percent of natural fixation many plants have symbiosis with N fixing bacteria
Industrial N fixation
Haber Bosch Process combines N2 with hidrogen under hig pressure to form ammonia, chemical fertilizer
Too much nitrogen
gulf of mexico dead zone; many nutrients transported by mississippi, too much enrichement, result phytoplankton blooms, oygen depletion (hypoxia) as algae dies and decomposes
Species diversity
a combination of the number of species and their relative abundence
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