LEC.145 Biodiversity and Conservation Flashcards
Which is the most diverse group of land plants?
Flowering plants (angiosperms)
What is the gradient of species richness?
Latitudinal from tropics to poles (except for some species e.g. seabirds most abundant/diverse in high latitudes)
What are the 4 hypotheses for there being more diversity at the tropics?
- Geographic area (shape of planet means more area at tropics)
- Energy-species (availability of resources + climate dictates no. co-existing species in given area)
- Rapoport’s Rule (geographic range of species decreases from poles-tropics)
- Evolutionary speed (tropics have had long time stability + faster rates of evolution)
What are 3 explanations for Rapoport’s Rule?
- Climatic variability greater at high latitudes so broad niche required to survive
- Glaciation (species with high dispersal ability repopulate north so have large geographic range)
- Competition between species (tropics have more competition so restricted habitat and small niches)
What are 4 ways of measuring biodiversity?
- Species richness (alpha diversity)
- Species composition (beta diversity)
- Phylogenetic diversity (higher diversity when species in community are less genetically related)
- Functional diversity
Define endemism
Species richness of rare species
Why are biodiversity measurements important?
Provide tools for selecting areas to prioritise for conservation
Define a biodiversity hotspot
Geographical area that ranks particularly high in species richness (also based on levels of endemism)
What is a complementarity approach?
Conserving as much biodiversity as possible in a limited area of land available for conservation
What is positively related to species richness and provides ecosystem services that are useful to humans?
Ecosystem functions
Define competitive exclusion
When most competitive species drives others to extinction
What are the 2 types of theories on regulation of local diversity?
- Equilibrium theories
- Non-equilibrium theories
What do non-equilibrium theories on the regulation of local diversity suggest?
That community diversity is due to processes that prevent equilibrium being reached i.e. interfere with competitive exclusion
What do equilibrium theories on the regulation of local diversity suggest?
That community diversity is regulated by processes of competition + evolution to attain a steady + stable state
What are the 3 equilibrium theories?
- Niche concept (specialisation enables more species to co-exist in a given area)
- Heterogenity (more diverse habitats have more niches e.g. vertical structure of trees)
- Island biogeography theory (species diversity = island area + isolation (balance between forces of immigration + extinction))
How does the species-area relationship influence extinction?
Forces of extinction decrease with size (higher resource abundance + habitat heterogenity)
How does isolation influence immigration?
Forces of immigration increase on near islands (speciation is more important on remote islands)
What are the 2 non-equilibrium theories?
- Diversity-productivity relationship (species richness unimodally related to productivity, peak diversity at intermediate productivity)
- Intermediate disturbance hypothesis (low disturbance = competitive exclusion, intermediate disturbance = max diversity due to prevention of competitive exclusion, high disturbance = low diversity as few species survive)
What is the dynamic equilibrium model?
Highest diversity under conditions where neither disturbance nor competitive exclusion dominate
What are the 2 types of succession?
- Primary (from sterile beginnings, non-living e.g. volcanoes, glaciers)
- Secondary (on previously colonised land after major disturbance e.g. landslides, fire)
What are the 2 types of succession process?
- Autogenic (species change due to interactions between organisms themselves e.g. competition)
- Allogenic (species change due to external, non-biological factors e.g. climate change)
Describe the traits of early successional species (colonisers, “r-selected”)
Small, fast-growing, produce many seeds, often no dormancy required (germinate if conditions are favourable), often N fixers e.g. lichens, cyanobacteria, allocate more energy to reproduction than biomass
Describe the traits of late successional species (competitors, “K-selected”)
Large, slow-growing, dormancy, large seeds, competitive (canopy species), allocate more energy to biomass than reproduction
Define seres
Successional stages with characteristic vegetation types + associated biota