Lecture 22 Summary

 Biological Diversity Defined- Biodiversity refers to variation among organisms and ecological systems at all levels:
1. Genetic Diversity
2. Ecological Diversity
3. Phylogenetic Diversity
4. Ecosystem and Biome Diversity

 Biodiversity refers to the variety and variability of the organisms living on Earth, in a narrow sense it can be thought of as the number of species on the planet.

 There are currently about 1.8 million species known to science but there are an estimated 10-30 million total species on Earth. The majority of large mammals have likely been discovered because man has been on the majority of the land covering the Earth. Whereas Ichthyologists describe about 300 new fish species each year.
o We need to being to focus on phyletic diversity instead of species diversity because this is where the real interesting diversity lies. Need to worry about the branches of the tree of life, not the tips.

 Geography of Life- number of species is greatest near the equator and declines as you move toward the poles; latitude gradients.
o Possible explanations:
 Glaciation- animals have been present in the tropical areas and thus have had more time to evolve and diversify
 Productivity-
• tropics are more productive (light, water, nutrients, more warm and wet) thus they can support more life and are relatively stable.
• Dry areas are water limited for primary production so they don’t have a solid base for the food web

 Predictable relationship between area and number of species
o 10x increase in area results in a double in the number of species

 Diversity:
o Alpha- the number of species in a location/habitat (# tress in the diag)
o Gamma- the total diversity in a region (# of trees in MI)
o Beta- diversity between habitat component, maximal if each habitat has a unique list of species (high species turnover)

 Colonization – extinction equilibrium
o Number of species found on an island is a balance between colonization and extinction processes
o At some point every species that can get to the island will have gotten there (declining colonization rate)

 Terms:
o Endemic species- species that only occurs in a small area

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