Biogeography

Biogeography

• Biogeography is the study of the geographical distribution of organisms. It seeks to understand why species are found where they are.

Theory of Plate Tectonics:

• Evidence:

• The Earth's lithosphere is divided into plates that move over the asthenosphere.

• This movement, driven by convection currents in the mantle, causes continental drift.

• Mid-Atlantic Ridge:

• Fossil Distribution:

Mid-Atlantic Ridge

: A divergent plate boundary where new oceanic crust is formed, pushing continents apart.

Fossil Distribution:

Similar fossils found on widely separated continents provide evidence of past land connections. These distributions help to show past continental connections.(shit moves)

Biogeographic Regions

• Examples and Boundaries:

• Large-scale areas of the Earth's surface characterized by distinct assemblages of plants and animals, reflecting evolutionary history, geology, and climate. (funal boundary separates them)

• Wallace's Line:

• Convergent Evolution and Similar Habitats:

Wallace's Line:

• A significant faunal boundary separating the Indomalayan (asia) and Australasian (australia) realms, highlighting distinct evolutionary histories.

• Convergent Evolution and Similar Habitats:

• Chaparral (California)

• Matorral (Chile)

• Lowland Fynbos (South Africa)

• Kwongan (Southern Australia)

• Maquis (Mediterranean basin)

• These regions, despite their geographic separation, share similar climates, leading to convergent evolution of plant communities.

• Native:

• egs

• Naturally occurring in a given place.

• Example: Aphelocoma californica (Western Scrub-Jay) in Los Angeles.

• Introduced:

• egs

• Occurring in a given place as a result of human influence.

• humans brought it

• Example: Amazona viridigenalis (Red-crowned Parrot) in Los Angeles.

• Example: Callipepla californica (California Quail) in Hawaii.

• Endemic:

• egs

• Geographically restricted to a given place.

• found only there

• Example: Aphelocoma californica (Western Scrub-Jay) in western North America.

• Example: Amazona viridigenalis (Red-crowned Parrot) in Northeastern Mexico.

• Example: Callipepla californica (California Quail) in western North America.

• Note: All terms are relative to a specific place of reference.

• Continental Drift and Fossil Distribution:

• Patterns of fossil distribution reflect past continental connections and movements.

• This helps to reconstruct the evolutionary history of organisms and their dispersal.

• finding parts of puzzle piece = once part of same puzzle

• Habitat Convergence:

• The prescence of similar habitat types in geographically distant regions, such as the various shrubland examples, that show how similar environmental pressures create similar patterns of life.

• less water = adaptations → convergent evolution= simialr traits and anatomy but nto same lineages

• Wallace's Line:

• A very clear line that shows a pattern of drastically different animal populations, due to past geological isolation.

• this reflects geological isolation = diff evolutionary paths -> fence between Asia and australia

• bc tectonic plates

• deep water

• continental shelf

Genetic Drift

key characteristics

• Definition: Random fluctuations in allele frequencies within a population over time, primarily due to sampling effects in finite populations.

• random lottery for genes thr chnage in how diff versions of genes (alleles) show up bc chance

• Key Characteristics:

  • Driven by chance.

  • More pronounced in small populations. bc its easier to change gene pool with random effects bc less pop

• Founder Effect:

• few individuals → from larger populations move and start new → group = diff genes bc chance (or less genetic variation)

• Change in allele frequencies resulting from sampling effects when a small number of individuals colonize a new area.

• Leads to a new population with potentially different allele frequencies than the original population.

Bottleneck Effect:

• Change in allele frequencies due to a significant reduction in population size (e.g., natural disasters).

• Reduces genetic variation in the population, including subsequent generations.

• Example: Mirounga angustirostris (Northern Elephant Seal)

• Example: Acinonyx jubatus (Cheetah)

• → surving a disaster with limited genes bc only whos left

• if something happens = pop smaller → survivors migght not have op pop to full genertic diveristy = bottle neck which reduced genetic veraton