Ecosystems, Populations, and biodiversity

SCI 7724

Case Study: Costa Rica Cloud forest

What is evolution, really?

Natural selection

Natural selection works on POPULATIONS

Evolution can generate biodiversity

What is speciation and how does it happen?

Population separation

Allopatric speciation

• Sympatric speciation

Phylogenetic trees

Mass extinction events

• Most extinction occurs gradually– background extinction rate

• Mass extinctions can wipe out 50-95% of biodiversity

• 65 mya- K-T event• 250 mya- 75-95% of species extinct- volcano?

The sixth mass extinction

• http://www.well.com/~davidu/extinction.html

Levels of ecological organization

• Biosphere• Ecosystem• Community• Population• Individual

Niches

What’s so important about niches?

Population size

• How is it calculated/estimated?• Why is it important?

Population density

• How is it calculated/estimated?• Why is it important?

Population distribution

• How is it calculated/estimated?• Why is it important?

Sex ratios and age structure

• Why does it matter?

How populations change over time

Limiting factors and carrying capacity

R- and K-selected species

Conservation of Biodiversity

• Cloud forest

Interpreting graphs