Lecture 4: Community Dynamics Flashcards
(19 cards)
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
