1. Unit 3
Biodiversity Section

2. Evolution is the mechanism underlying biodiversity
Evolution- a change in the genetic composition of a population over time.
Microevolution- evolution below the species level.
Macroevolution- Evolution which gives rise to new species or new genera, family, class or phyla.

3. Biodiversity
Case Study-Siberian Tigers—Loss of habitat and potential biodiversity. Biodiversity looks at the diversity of the species; their genes, their populations, their communities.

4. Earth is home to a tremendous diversity of species
Ecosystem diversity- the variety of ecosystems within a given region.
Species diversity- the variety of species in a given ecosystem. Speciation, the generation of a new species; increases biodiversity.
Genetic diversity- the variety of genes within a given species.

7. Which community has a greatest diversity?
Biodiversity: the number of different species in a given area – a measure of the health of the environment.
Species richness- the number of species in a given area.
Species evenness- the measure of whether a particular ecosystem is numerically dominated by one species or are all represented by similar numbers of individuals.
Which community has a greatest diversity?

8. Biodiveristy is unevenly distributed
Living things are distributed unevenly across Earth
Latitudinal gradient = species richness increases towards the equator

9. Biodiversity losses and species extinction
Extinction = occurs when the last member of a species dies and the species ceases to exist
Extirpation = the disappearance of a particular population from a given area, but not the entire species globally
Can lead to extinction

10. The Five Global Mass Extinctions
Mass extinction- when large numbers of species went extinct over a relatively short period of time.

11. The Sixth Mass Extinction
Scientists feel that we are in our sixth mass extinction, occurring in the last two decades.
Estimates of extinction rates vary widely, from 2 % to 25% by 2020.
In contrast to previous mass extinctions, scientists agree that this one is caused by humans.

12. Biodiversity Causes
Reasons for biodiversity losses are multifaceted, complex, and hard to determine
Factors may interact synergistically
Four primary causes of population decline are:
Habitat alteration-many man-made
Invasive species-non native species introduction-Fig 11-13
Pollution-Air, Water…
Overharvesting—over hunting…
Global climate change now is the fifth cause

13. Biodiversity provides free ecosystem services
Provides food, shelter, fuel
Purifies air and water, and detoxifies wastes
Stabilizes climate, moderates floods, droughts, wind, temperature
Generates and renews soil fertility and cycles nutrients
Pollinates plants and controls pests and disease
Maintains genetic resources
Provides cultural and aesthetic benefits
Allows us to adapt to change

14. Biodiversity generates economic benfits
People like to experience protected natural areas, creating economic opportunities for residents, particularly in developing countries
Costa Rica: rainforests
Australia: Great Barrier Reef
Belize: reefs, caves, and rainforests
A powerful incentive to preserve natural areas and reduce impacts on the landscape and on native species
But, too many visitors to natural areas can degrade the outdoor experience and disturb wildlife

15. Island Biogeography
Equilibrium theory of island biogeography = explains how species come to be distributed among oceanic islands
Also applies to “habitat islands” – patches of one habitat type isolated within a “sea” of others
Explains how the number of species on an island results from an equilibrium between immigration and extirpation
Predicts an island’s species richness based on the island’s size and distance from the mainland

16. Island Biogeography
Fewer species colonize an island far from the mainland
Large islands have higher immigration rates
Large islands have lower extinction rates

18. Major Legislation
Endangered Species Act (1973) (ESA) = forbids the government and private citizens from taking actions that destroy endangered species or their habitats
To prevent extinction
Stabilize declining populations
Enable populations to recover
As of 2007, the U.S. had 1,312 species listed as endangered or threatened

19. Protecting Biodiversity
Captive breeding – individuals are bred and raised with the intent of reintroducing them into the wild
Zoos and botanical gardens
Some reintroductions are controversial
Ranchers opposed the reintroduction of wolves to Yellowstone National Park
Some habitat is so fragmented, a species cannot survive
Cloning

20. International Conservation Efforts
UN Convention on International Trade in Endangered Species of Wild Fauna and Flora (1973) (CITES) – protects endangered species by banning international transport of their body parts

21. Biodiversity Hotspots
Biodiversity hotspots – prioritizes regions most important globally for biodiversity
Support a great number of endemic species = species found nowhere else in the world
The area must have at least endemic plant species (0.5% of the world total)
It must have lost 70% of its habits impact

22. Biodiversity Hot Spots