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
What is the intermediate disturbance hypothesis?
Areas with intermediate levels of disturbance have the highest species richness
Why does low disturbance cause low species richness?
- Because more dominant species take over biomass without disturbance
- The population will only consist of dominating species
What are the main drivers of biodiversity decline?
- Climate change
- Pollution
- Invasive species
- Overexploitation
- Habitat destruction
Why should we care about biodiversity?
- Biodiversity is tied to ecosystem services
- More carbon sequestration
- Natural coastline protection
- More livelihoods
- A sense of place and wellbeing
