Chapter 8

Biogeography

Niche Explains how so many species can coexist –

as the competitive-exclusion principle states that : Two species that have exactly the same

requirements CANNOT coexists in exactly the same habitat

Species that require the same resources can coexist by utilizing those resources under different environmental conditions.

Habitat complexity allows for this ie: a habitat they has, for example, varying

temps. or precip.

Habitat vs. Niche WHERE a species lives, is its habitat,

WHAT type of conditions a species lives under is its ecological niche (the sum of all of the rages of tolerance under which it can survive – temp., climate, food sources)

If we want to conserve species, then we need to ensure all of the requirements of its niche are present

Species Diversity Species are not uniformly distributed

over Earth’s surface. Biogeography - the large scale pattern

in the distribution of species Terrestrial species and ecosystems

change depending on soil, topography, elevation, etc.

Ecological Gradiant – Change in the relative abundance of a species over an area or a distance Pg. 134 in text

Factors the INCREASE Biodiversity

Physically diverse habitat Moderate amounts of disturbance, ie: fire Small variation in environmental

conditions – temp. precip A high diversity at one trophic level

increases the diversity at another An environment highly modified by life,

ie: rich organic soil Middle stages of succession evolution

Factors the DECREASE biodiversity Environmental stress Extreme environments Severe limitation in a supply of an

essential resource Extreme amounts of disturbance Recent introduction of an exotic species

(species from other area) Geographic isolation (a real or

ecological island)

Early ideas regarding biogeography:1749Linneaus – 1st scientific botanist, father of taxonomyQuestioned: Why was there more variety in plant species in N. America and China and not Europe? They had similar climates ??

Explained by the Theories of Biogeography

Alfred Wallace 1876 British Biologist Co-discoverer (w/ Darwin) – “Theory of

Evolution” Big idea -- World is divided into 6

geographical regions (realms), based on fundamental features of the animals found in those areas

Wallace’s Realms: Biotic ProvincesRealm:

Major biogeographic regions of Earth that are based upon fundamental features of the plants and animals found in those regions

Taxa: Categories that identify groups of living organisms

based upon evolutionary relationships or similarity of characteristics (ex: species, families, orders)

Biotic Provinces: A geographical region (realm) inhabited by a

characteristic set of taxa, bounded by barriers that prevent the spread of those distinctive kinds of life to other regions.

6 Biogeographic Regions Nearctic Neotropical Palaearctic Ethiopian Oriental Australian

Known as “Wallace’s Realms” Patterns in animals was the first step

The main biogeographic realms for animals are based on genetic factors .

The major vegetation realms are also based on genetic factors

Relationship among living thingsAll living things are classified into

groups calledTaxa:

Categories that identify groups of living organisms based upon evolutionary relationships or similarity of characteristics (ex: species, families, orders)

KPCOFGS

Realms Certain families are dominant Animals of these families fill particular

ecological niches Animals of different genetic stock fill the

same niche in other realms

EXAMPLE:Large Mammalian Herbivores Bison N. America Capybara S. America Kangaroo Australia Giraffe S. Africa

All in the same family All fill the same niche, in differing areas

Biotic Provinces Realms are now referred to as Biotic

Provinces A region inhabited by organisms with

the same taxa (sp. , fam. Order) Organisms share common genetic

heritage Provinces are bounded by barriers that

prevent spread to different regions and immigration from foreign species. HOW IS THIS EXPLAINED??

Continental Drift All due to continental drift Wallace did not know this at the time

The unification of the continents (Pangea) allowed for genetic mixing. Enabled organisms to enter new habitats.

Separation, imposed genetic isolation and the evolution of new species.

Convergent EvolutionGiven sufficient time

and similar climates in different areas, species similar in shape and form will tend to occur.

Example: Joshua TreeSaguaro CactusEuphorbiaAll tall with green

succulent stems that replace leaves. Not closely related – different families.

Evolution under similar desert climates – convergent evolution

Divergent Evolution Organisms with the same ancestral genetic

heritage migrate to different habitats and evolve into species with different external forms and structures, but continue to use the same type of habitats

Ex) Ostrich (Africa), emu (Australia) and rhea (s. America) - all evolved separately, but retain some common characteristics.

Population divided, usually by geographic barrier. In open grasslands, a lg. bird that can run

quickly, feed on small seeds and insects had advantages over other organisms seeking the same food.

Biomes Biogeographic pattern Kind of ecosystem Similar environments provide similar

opportunities for life and similar constraints

Lead to evolution of organisms similar in form and function.

Island BiogeographyTheory of Island Biogeography

Islands have fewer species than continents The smaller the island, the fewer the species New species on an island are a result of migration

and/or evolution The farther the island is from the mainland, the fewer

the species

Why?? Fewer habitats Some habitats are too small to support a

population large enough to survive Small populations are easily extinguished –

flood, fire Smaller the population, the greater the risk of

extinction Farther an island is from mainland, the harder

it will be for an organism to travel the distance A small island is a small “target” – less likely

to be found Islands tend to maintain a constant # of

species

Adaptive Radiation:

The process that occurs when a species enters a new habitat that has unoccupied niches and evolves into a group of new species, each adapted to one of these niches.

Finches on the Hawaiian Islands – 16 species, each with specialized beaks for its food.

Ecological Island: An area that is biologically isolated so that a

species occurring within the area rarely mixes with any other population of the same species

Ex. – ponds, city park, small stand of trees in a field

Earth’s BiomesThe Earth has 17 major biomes , each

with its own characteristic dominant shapes and forms of life.

Most biomes have been heavily altered by human action.

People have introduced exotic species to new habitats – sometimes creating benefits, often creating problems

Primary Rule: Unless there is a clear and good reason to introduce an exotic species into a new habitat, don’t do it.

17 Major Biomes1. Tundras

- treeless plains that occur in the harsh climates of low rainfall and low average temperature- two types: artic tundra and alpine tundra- parts have permafrost: permanently frozen ground

2. Taiga or Boreal Forests- includes the forests of the cold climates of high latitudes and high altitudes- dominant life forms including moose and other large mammals, small flowering plants and trees

3. Temperate Dedicious Forests- occur in warmer climates that the boreal forest

4. Temperate Rainforest- moderate temperatures, over 250 cm/year of rain

5. Temperate Woodlands- Slightly drier climate that the deciduous forests- fire is common and species adapt to it

6. Temperate Shrublands- also called chaparral: miniature woodlands

7. Temperate Grasslands- include many North American parries

8. Tropical Rain Forests- high average temperature and rainfall

9. Tropical Seasonal Forest and Savannas- high average temperature, low latitudes, abundant but seasonal rainfall

10. Deserts- The driest region that vegetation can survive.

11. Wetlands- Include freshwater swaps, ,marshes and bogs – all have standing water

12. Freshwaters- Have phytoplankton and estuaries

13. Intertidal Areas- Areas exposed to alternately to air during low tide and high tide

14. Open Ocean- Also called the pelagic region

15. Bethos- Bottom portion of the ocean

16. Upwellings- Upward flows of ocean water

17. Hydrothermal Vents- Occur in the deep ocean were plate tectonic processes create vents