Lecture 4: Community Dynamics Flashcards
What do food webs represent?
Tropic interactions between organisms
What does the vertical position of an organism in the food web represent?
Trophic level
What is a focal species?
A species that plays a disproportionate role in the food web
Dominant species
Species with a high biomass
Ecosystem engineers
Alter the physical environment
Keystone species
- Despite low abundance and abundance
- Usually top predators
- Important to the other species around them
Top-down control
Higher trophic level reduces abundance or biomass of lower trophic level
Trophic cascade
Impact of top predators extends to lower trophic levels
Regime shift
Abrupt shift to a very different and persistent community
- Hard to reverse
What causes regime shifts?
- Removal of keystone species
- Arrival of species
- Climate change
- Nutrient inputs
Bottom-up control
Lower trophic level controls abundance or biomass of higher trophic levels
Species richness
Number of species present in a community
Biodiversity
The variability among living organisms from all sources
- Diversity within species, between species, and of ecosystems
Where is the world’s biodiversity found?
Around the equator
Why is there a latitudinal gradient in species richness?
- Origin of life is near equator
- Historical adaptation to tropical environments
- Higher and more storable temperatures
- Stable environmental conditions
