• mutualism ++
• commensalism +0
• parasitism +-
  

parasites - Eat only a portion of the host, many per host, usually dont kill host.

parasitoids - eat almost entire host, couple per host, usually kill host

• holo - no longer photosynthesize, but get all food and water from host
• hemi - parasites for water and minerals, but photosynthesize to make their own food

• what is so unique about parasitoids?

• 10% of world species diversity
• biocontrol
• larvae emerge from dead hosts
• hyperparasitoids

• reduced clutch size
• male flashiness has good genes to fight off parasites
• less fit to survive
• alter behavior to increase mortality

• host in a parasitic relationship evolves to not be negatively affected by parasite anymore

facultative vs. obligate mutualists?

generalists vs. specialists?

• fac - can live w/o each other
• obl - need each other to survive
•  gen - one species can replace another
• spec - needs to be a specific species

4 categories of mutualism?

• superficial
• within organism but extracellular
• intracellular; separate genomes
• intracellular; share genomes

plants - get root extensions to increase SA for uptake of water and minerals

fungi - get a home with organic carbon source

How do plants acquire Nitrogen?

what conditions needed?

example of?

• N2 converted to NH4 via bacteria
• bacteria housed in anaerobic nodules on roots where leghemoglobin uses nitrogenase enzyme to convert nitrogen
• example of intracellular but separate genomes

• species richness
• relative abundance - % of species pop. in entire pop.

simpsons index?

• measures species diversity
• probability of selecting two of same species
• D = Sum(n1/N)^2
• sum of all species( number of ind. in sp1/total # of ind.)^2
• Ds = 1 - D
• Ds = species diversity

• measures both species richness and evenness
•  H' = -sum (pi)(lnpi)
• pi = n1/N

• alpha - diversity within a community
• beta - diversity between communities, habitats, ecosystems( # of species unique to each community)
• gamma - diversity within a geographical area (# of total species)

• CC coefficient of community
• CC = 2(Common sp)/(#sp in c1 + #s2)

• changes observed in physical and biological structure across a landscape

What determines Community strucutre?

2 concepts?

• clements organismic concept - species interactions big part of community structure
• gleason's individualistic concept - species respond to resource and nutrient availability in environment, species interaction not important

Keystone species concept?

keystone predator?

• one species has a larger impact on the community than thought by looking at mere abundance.
• beavers
• indirect effect of a predator on non-prey organisms ( starfish removal affects other bivalves)

• apparent competition
• indirect commensalism
• indirect mutualism

• addition of prey species will increase predator population
• this will decrease both prey populations
  - makes it look like competition between prey pops because pop. is smalller than if it was just one prey population.

indirect commensalism?

• Salamander feed on large daphnia
• midge feed on small daphnia
• daphnia compete
• salamander deplete large daphnia increases amount of small daphnia
• midge population positively affected
• salamander not affected

species a, b and c

• negative effect of species a on b + affects c
• negative effect of species c on b + affects a

food web terminology:

links

basal species

intermediate

top predator

• links - point from the species being eaten to the predator
• basal - species that are eaten and dont eat anything (plants)
• intermediate - eaten and eat others
• top - eat others but not eaten (humans)

index of connectance

link density

C = L/[S(S-1)/2]

S= # of species in food web

L = # of links

link density = L/S

• bottom up - bottom of food chain determines top,
• top-down - predators high on the trophic level will determine prey population low in the trophic level

even number of trophic levels = more

odd number of trophic levels = more..

 top down

bottom up

sere

seral stage

climax

• orderly stages of a community changing through succession
• a community in a sere ( years to a decade)
• final seral stage or mature ecosystem

• dispersal activity - ability to inhabit an area before another species
• competitive ability - ability to outcompete a species for a given area

• Pioneer - high growth rate, high reproduction rate, high dispersal rate, small
• climax - slow growth rate, low reproduction rate, large, low dispersal rate, longer lived

two types of succession?

convergence?

• primary - community development in a previously unoccupied territory (dried up lake, lava flow, new lake)
• secondary - community development after a disturbance (fire, landslide, logging, agri.)
• convergence - the progression of a community toward the prevailing biome of the region

• allogenic ( no origin) - caused by fire, storms leads to secondary succession.
• autogenic (self-origin) - caused by an organism within the system (locust plague, outbreak herbivores(gypsy moths)

early theories of succession:

-monoclimax hypothesis?

-floristic composition hypothesis?

• mono - community is "superorg" that gradually shifts into climax ecosystem
• flor - depends on who gets there first, no competition, when pioneers die, climax replace

facilitation model?

inhibition model?

tolerance model?

• fac - pioneer species alter the nutrient and resource environment of the community allowing for climax species to inhabit
• inhib - pioneer species competitively exclude the climax species, pioneers die off due to disturbances and climax eventually take over
• climax species neither inhibited or aided by early species. climax species can survive with less resources and eventually outcompete early species

intermediate disturbance hypothesis?

high disturbance favors who?

low?

when disturbances occur it allows for the integration of new species into the community

high disturbance rate = lots of pioneer species

low d rate = lots of climax species

mosaic

patch

• mosaic- patchwork of different types of land
• patch - homogenous habitat

• inherent - natural
• induced - created by disturbance
• convoluted border - curvy
• perforated - gaps
• wide - large gradient (ecotone)
• narrow - small

• more species in ecotone than in either patch

• some species endemic to ecotone

• two factors colonization and extinction are affected by distance from mainland and island size

im = distance from mainland

ex = island size