1. Biodiversity How did biological diversity come about?
What are the principles of natural selection?
What affects biodiversity?

2. What is biological diversity?
1. genetic diversity
2. species diversity
3. higher taxonomic diversity (taxonomy)
4. habitat diversity
1. genetic diversity
the gene pool of a population or a species
2. species diversity
numbers and types of different species (species richness, species evenness, species dominance)
3. higher taxonomic diversity
numbers and types of broader classification categories
taxonomy
practice of naming, describing and classifying organisms
built on a system of relatedness to reflect evolutionary histories
4. community or habitat diversity
Number of different communities or distinct habitats within a defined area or ecosystem.

3. How many species exist in the world?
No one knows!
Taxonomists have named and described million species
56% insects
14% plants
3% vertebrates
15% are in oceans
Highly biased sample
Vertebrates much more widely studied
What about microbes?
4000 different bacteria species per gram of Norwegian soil!
Also, mostly done in Europe and N. America while most of the biodiversity is in tropical countries and in oceans
250,000
500,000
750,000
1,000,000
insects
other animals
higher plants
fungi
protists
viruses
bacteria

4. So how many species are there?
14 mil
15,000,000
however, this number could be as high as 100,000,000
number of species
10,000,000
5,000,000
1.7 mil
Total number identified = 1.4 – 1.75 million
Working number = 14 million
Estimates range from million!
total identified
total estimated to exist
Global biodiversity seems to be at its peak

5. Where are these species?
Oceans
1 to 10 million in oceans
diverse in phyla
32 in oceans but only 12 phyla on land
Tropics
7% of land mass
50% of species

6. How do species evolve?
Evolution is the change in the genetic characteristics of a population over time.
This change may happen by:
genetic mutations
natural selection
geographic isolation and migration
genetic drift (most likely in small, isolated populations)
Genetic mutation: changes in the structure of DNA that happens in one individual (can be passed down):
Causes: radiation, chemicals, viruses.

7. Views of Species Change: Evolution
Organisms today descended by gradual changes from ancient ancestors.
Age of the Earth: 238Uranium half-life of 4.5 billion years, current amount present suggests earth is ~ 4.6 billion years old (…so what?)
Views of Species Change: Evolution
Lamarck (1809)
Use and disuse
Inheritance of acquired characteristics
Charles Darwin (1859)
Alfred Wallace

8. Principles of Natural Selection
Genetic variation exists among organisms in a population, these variations are inheritable.
Populations produce more offspring than environment can support and therefore only a fraction survive (struggle for existence)
Individuals best adapted to environment (more “fit”) will survive and leave more offspring
…..“Survival of the fittest”

9. Examples of natural selection
Moths: “industrial melanism”
DDT and mosquitos
What is “fit” changes with a changing environment

10. Galapagos finches Variety of finches filling many ecological niches
Ground feeders, flower and fruit feeders, insectivores, woodpecker finch, warbler finch
Evolutionary divergence in < 3 million years

11. Island speciation in Galapagos finches
Some islands have only one species
No competition for seeds
beak sizes have a larger range of variation
“Generalists”
Other islands have > 1 species
Competition for seeds
Leads to character displacement to reduce competition
“Specialists”

12. Character displacement and biodiversity
Helps explain how so many species are able to coexist
Competitive exclusion principle: Two species that have exactly the same requirements (niches) cannot coexist in the same habitat.
However, species that require the same resources can coexist by utilizing those resources under different environmental conditions (or niches)
Also called “resource partitioning” or “niche partitioning”
American gray squirrel outcompeting the native British red squirrel – same exact habitat requirements
How invasive species relates to this.

13. Speciation Speciation = origin of new species
Central phenomenon of evolution
Evolution ≠ speciation
When is a subpopulation defined as a new species?
How do genes usually flow through a population?
Reproductive isolation prevents gene flow and allows 2 populations to become distinct.

14. Geographic isolation and migrationb u C c i L . l f o T x G y
If two populations are geographically isolated from each other for a long time, they may change so much that they cannot reproduce

15. Genetic drift
Changes in the frequency of a gene in a population due to chance (not mutation, natural selection, or migration).
Mostly an issue in small populations (endangered species)
Genetic variability is low in small populations, so their ability to adapt to future changes in the environment is low.

16. Where can expect to find high biodiversity or low biodiversity?

17. Higher diversity in complex environments
Larger number of niches in heterogeneous environments
Also, high diversity at a supporting trophic level leads to high diversity.

18. “Paradox of the Plankton”
seemingly simple environment, many species, no competitive exclusion
environmental complexity can still account for significant portion of diversity
need just two limiting resources

20. Environments can be complex when spatial component added

21. Highest diversity at intermediate disturbance levels
Intermediate Disturbance Hypothesis
low disturbance, competitors dominate
high disturbance, only a few stress-tolerators

22. Highest Diversity in Low Nutrient Environments

23. What leads to low diversity?
Environmental stress, extreme environments, extreme disturbance, or limitation of an essential resource
Geographic isolation (real or ecological islands)
Recent introductions of exotic species