Community Ecology II: Food Webs & Diversity Flashcards
What controls primary production? (growth of plants/algae)
- nutrients (nitrogen and phosphorus)
- grazing by zooplankton
Top down control
Zooplankon grazing on algae (zooplankton is above algae on the food chain)
Bottom up control
Algae absorbing nutrients (the nutrients are below algae on the food chain)
Trophic cascades
Indirect effect of top predators on lower trophic levels
Dominant species
Species that are most abundant or have the highest biomass
Keystone species
Species that exert strong control on a community by their ecological roles or niches (i.e. sea stars)
Biomass
The total mass of all individuals in a population within a community/weight of living organisms
Ecosystem engineers
Influence other species by physically altering the environment
Biodiversity
The variety of all life forms
Species diversity
- richness = total number of species in a given area
- evenness = distribution of individuals among different species in a given area
Patterns of diversity: (2 patterns)
- habitat size
2. poles -> tropics
Habitat size
Species-area curves
Poles -> tropics
Less diverse -> more diverse
The biodiversity crisis
Current rates of extinction are unusually high
Mutational meltdown and extinction vortex
Positive feedback system: small populations tend to get even smaller
-intervention: reintroducing species from other populations (new genetic variability)
Causes for modern extinction: (3 causes)
- habitat destruction
- introduced (invasive, exotic) species
- overexploitation
Habitat destruction
- loss
- fragmentation
Introduced/exotic species
Species introduced to an area outside of their native range
Invaders (invasive species) can: (3 things)
- alter habitats
- reduce or displace native species
- alter ecosystem services
- i.e. kudzu (southeastern U.S.)
Common features of invasive species: (4 features)
- wide environmental tolerances
- large native range
- high rate of population increase (r)
- predator resistance/abundance
Biotic homogenization
Via trade or intentional transports is like to contribute to establishment of invasive species
Overexploitation
Harvesting of plant, animal populations at higher rates than population growth rates
Solutions to modern extinction: (4 solutions)
- education and awareness
- biodiversity reserves
- reduce overexploitation
- restoration and remediation
Reserves (conservation of 5 things)
Goals = conservation of:
- large, intact, functioning ecosystems
- areas of high biodiversity
- species or groups of species of special interest
- significant and natural communities
- important ecosystem services
