Biogeography-A

Biogeography

Earth’s History

  • Significant Event: 65.5 million years ago marked a major extinction event.

  • Context: This event is classified as the most recent of multiple major extinction events in Earth's history.

Number of Species

  • Species Estimates:

    • May suggests there are 5-10 million species.

    • Other estimates range from 3 to 100 million species.

Biogeographic Regions

  • This section discusses the classification of biogeographic regions, details not provided in the text.

Counting Species

  • Species Accumulation Curves:

    • A method for visualizing the accumulation of species within a given area over time.

Local Species Diversity

  • Question: What factors determine local species diversity?

  • Proposed Drivers (by Witman):

    • Two non-mutually exclusive mechanisms:

    • A:

      • Alpha Diversity: Represents the number of species in a specific site (e.g., a wall).

      • Relies on the size of the Gamma Diversity (the regional species pool).

      • Each time space opens up, it can be colonized by species from this regional pool, determined by rates of speciation and extinction.

    • B:

      • Alpha diversity is also influenced by local species interactions, including:

      • Competition for space and resources.

      • Predator/prey dynamics that determine survival and colonization success of species.

Species Turnover

  • Definition of Alpha Diversity: Needs to be defined (details not provided).

  • Definition of Beta Diversity: Needs to be defined (details not provided).

Modern Extinction Crisis

  • IUCN Red List (Threatened):

    • Mammals: 21% threatened

    • Birds: 12% threatened

    • Reptiles: 6% threatened

    • Amphibians: 29% threatened

    • Fishes: 6% threatened

    • Overall: 33% of all evaluated species are threatened.

  • Example Case:

    • Hawaiian Islands: 56 endemic bird species extinct.

    • Pacific Islands: Approximately 2,000 birds (20%) estimated to have gone extinct due to various causes.

Why Protect Biodiversity?

  • Key Reasons:

    • Serves as a genetic library.

    • Provides crucial ecosystem services.

    • Represents an aesthetic and ethical obligation to protect life.

Species Area Curve

  • Research Question: What is the relationship between species diversity and the area of a habitat?

Equilibrium Theory of Island Biogeography

  • Details provided regarding the theory, but specific content is not available in the text.

Other Uses of Island Biogeography

  • Key Applications:

    • Forest Fragmentation: Impacts of breaking up habitats.

    • Reserve Design: How to effectively design environmental reserves.

Historical Biogeography

  • Timeline: 150 million years ago during the Jurassic period to the present.

  • Major Concepts:

    • Isolation of landmasses, such as Gondwana, led to unique evolutionary paths.

    • Mechanisms of speciation include:

    • Vicariance: geographic separation leading to speciation.

    • Allopatric Speciation: speciation due to physical separation.

Jump Dispersal and Founders Effect

  • Concepts Defined:

    • Jump dispersal refers to the movement of species across significant distances leading to colonization.

    • This is still a form of allopatric speciation.

Marsupials

  • Global Distribution:

    • Found in regions: North America, South America, Africa, Australia, Antarctica, and Asia.

Sympatric Speciation

  • Definition: A form of speciation occurring within a shared habitat.

  • Comparison: Differentiated from allopatric speciation, which occurs due to geographic separation.

Great American Biotic Interchange

  • Timeline: Began approximately 3 million years ago.

  • Key Facts:

    • Northern Costa Rica played a crucial role in connecting North and South America.

    • This event significantly impacted ocean circulation and facilitated the exchange of flora and fauna between continents.

  • Faunal Composition after Event:

    • In South America, approximately 50% of animals have North American roots.

    • In North America, about 10% of animals have South American roots.

Human Accelerated Dispersals

  • Concept: Discussion on the rapid spread of species due to human activities.

Number of Species and Latitudinal Diversity Gradiients

  • Graphs Discussed:

    • Illustrated patterns of species diversity across latitudes, focusing on mammals and trees.

  • High and low species count variation across different latitudinal zones.

Biodiversity Hotspots

  • Key Regions:

    • Polinesia-Micronesia, California Floristic Province, Tropical Andes, etc.

    • Many hotspots are identified for high endemic plant species and threatened animal populations.

Differential Energy and Ecosystems

  • Influence on Ecosystems:

    • Orbital tilt impacts seasonal changes affecting species distribution and ecosystem dynamics.

    • How radiation from the sun is dispersed affects surface temperature and weather patterns across the earth.

Air Circulation Cells

  • Overview of Atmospheric Circulation:

    • Equatorial Region: Intense solar heating causes warm, moist air to rise.

    • 30° North and South: As air rises, it cools and precipitates over tropical regions, creating moist climates.

    • This dry air leads to desert formations at 30° latitude.

    • Polar Cells: Similar to Hadley cells but operate at higher latitudes with less intensity.

References

  • Source: Information compiled from lecture materials by Dr. Greg George, drawn from Jon Herron and Eli Meir's publication "SimUText Ecology" (2010).