exam 2 Flashcards
community
group of various species in a common location at the same time
what is the difference between species richness and species diversity?
species richness: # of species in a defined region
species diversity: measure of abundance (shannon’s h index)
what is community stability?
ability of a community to defy change or rebound to equilibrium from change
what does a community in community stability have?
1) equilibrium stable over time
2) return to equilibrium after a disturbance that alters community structure
succession
process of directional change in communities over time and includes:
1) regular change in community composition (have life introduced to a new area)
2) one set of species succeeds a previous set (one paves the way and gets replaced)
ecological succession
the process of change in the species structure of an ecological community over time
-gradual change in plant communities in an area following a disturbance
sere
each stage of change (chunk of time)
climax community
a late successional community that remains stable until disrupted
1) not prone to invasion by non-climax species and can “renew” themselves
2) determined by the interaction between plant species and abiotic factors
ex: Sonoval desert in AZ and CA
primary succession
-occurs only on newly exposed geological substrates not yet modified by organisms
-where bare rocks have not seen presence of primary producers
-ex: lava flow, new lake after glacial retreat
seconday succession
-following disturbance that doesn’t destroy soil
-life has already existed and something disturbed it
-ex: harvesting, deforestation, hurricanes, and forrest fires
pioneer community
made up of very first species to colonize an area in successional sequence
pioneer plants characteristics
-hardy
-short life cycle
-high rate of dispersal
-easy to germinate (seeds can land anywhere and grow)
-opened to wind pollination
what is the order of nitrogen fixation?
1) nitrogen fixation
2) NO2 (nitrogen dioxide)
3) NH3 (ammonia)
characteristics of succession
1) increase in species diversity
2) changes in species composition
3) change in ecosystem properties
4) soil changes
what are some soil changes in succession?
-soil depth gets deeper for large root systems
-nitrogen, moisture, and organic matter increase
-phosphorous, pH, and bulk decrease
why does nitrogen increase with succession?
more plants = more nitrogen fixation
why does phosphorous decrease with succession?
phosphorous is limiting and comes from weathered rocks
chronosequence
communities/ ecosystems with a range of times since disturbance
-once had hot spots but then started primary succession
When are nitrogen and phosphorous limiting?
N= early succession
P= late succession
what are the 3 mechanisms of succession?
facilitation (most well accepted)
tolerance (survivor like- those can handle the change)
inhibition- no one superior. just whoever gets there first
facilitation
-only certain species can colonize (pioneers) which modify environment
-makes environment less suitable for themselves but easier for new species
tolerance
-initial colonization can have pioneers and juveniles of climax community
-later succession species are the ones tolerance of environmental conditions during succession
inhibition
-initial colonization can have pioneers and juveniles of climax community
-no one is superior. Just whoever gets there first
stability
absence of change
-due to resistance
resistance
ability to maintain structure and function in face of potential disturbance
resilience
ability to recover from disturbance
population
a single species inhabiting same place at same time
what does p= ?
frequency of a trait (0-1.0)
necessary resources to survive and reproduce
-water
-food
-CO2/ oxygen
-solar radiation
competition
Caused by reduction in quantity resources by activity of organisms
habitat vs niche
habitat= home
niche= job
habitat
-where the organism lives (its home)
-biotic and abiotic habitat
-ex: conifer forests, marsh, desert