Biodiversity

Biodiversity = "Biological diversity means the variability among living organisms from all sources including, inter alia, terrestrial, marine and other aquatic ecosystems and the ecological complexes of which they are part; this includes diversity within species, between species and of ecosystems."

○ A species richness

- Measuring biodiversity:

○ Number of species per area (ha)

§ Species evenness:

□ The same amount of species in a area, but the proportions are different

- est. 8.7 million species in the world (terrestrial and aquatic)

○ Based on avaiable data

§ Probably an underestimate...

- Small range species not taken into account:

○ Maybe only live in 1 m2

Discovering new species:

- Newly colonised lands

- Newly ordered taxonomy of species

○ Based on new research (genetic analysis)

- Allopatric specieation:

○ Diversity in species because of a barrier (human activity (hunting), mountainange, river...)

§ Isolates a population and evolve apart from each other

Curating biodiversity (preserving):

- Protected areas, museums, botanic gardens...

○ Not always organised

Biodiversity is greater in the tropics and decreseas near the poles...

- Latitude

Biodiversity decreases with altidude

- Also in tropical zones

• But in a desert:

- Biodiversity sometimes increases with altitude

Historical theroies of biodiversity:

- Pleistocene disruption:

○ Limited specieation

○ Extinction

○ Repeated disruption

§ T.d. Glaciation

Stability time hypothesis:

- The break in the cycle of glacitation should increase species' diversity and evolution

○ Aridity:

§ Cooler but still warm (pleistocene)

○ Fragmentation:

§ The forest that survived

○ Allopatric speciation

○ Ecotones (landamæri vistkerfa)

Equilibrium theories of biodiversity:

- Geographical difference in species is in regard to the present not past

○ Scale:

§ Geographical extent of topographic diversity

○ Niche:

§ Increased specialisation

○ Abundance:

§ Increased specialisation

§ Limited interspecific competition

Variables that influence biodiversity:

- Habitats and topography:

§ Different species in the hummock and hollow (mýri)

- Area:

§ Vegetation stucture

- Stability:

§ Limited variability (days, months, seasons, years)

§ Niche development

§ High variability (generalist)

- Disturbance:

§ Intermediate distubance hypothesis:

□ Optimum biodiversity:

® Competitive exlusion

® Limited distrubance

- Competition:

§ Reduced competition

□ Everyone is exploring their specialist niche

- Predation:

§ With reduced competiton:

□ More availability for predators to act

- Productivity:

§ High biomass (NPP)

□ Area can support more species with more resources (more diversity)

Theories of biodiversity:

- Historical theories cannot be exluded (not the sole responsible though):

- Climate change impact was global

- Disruption, displacement and extinction in mid-high latitudes

- Fragmentation promoted allopatric specieation in low latitudes

- Climate gradient

- Evapotranspiration

- >NPP

- Low seasonal variability

- Competition

Predaiton