What Shapes an Ecosystem? 4.2

Biotic vs. Abiotic Factors  Biotic Examples  Trees  Grasses  Weeds  Birds  Snakes  Fish  Bacteria  Abiotic Examples  Temperature  Precipitation  Nutrient  Dirt  Rock  Humidity  Sunlight

Habitat vs. Niche  Habitat  Organism address only!  Contains abiotic and biotic factors directly affecting the organism  Niche  Includes habitat AND place in the food web  How the organism lives and uses the physical and biological conditions  What it eats, how it gets food, interactions, reproduction, etc.

Can any 2 species occupy the same niche?  NO! See the warbler example-  For many years it was thought that 5 species of warblers occupied the same niche. Robert MacArthur set out to learn more. As the rule of competitive exclusion goes:  two species with essentially the same niche cannot coexist because one will always out- compete and displace the other.

How did he do this?  “ By measuring distances down from the top and outward from the trunk of individual spruce, fir, and pine trees, MacArthur divided the trees into zones and recorded feeding positions of the different warblers within each. A record in zone "T3" indicated a bird feeding among the abundant new needles and buds of the tip of a branch, between 20 and 30 feet from the top of the tree. A record of "M3" signified feeding mostly among dead needles at the same height but in the middle zone of a branch. A record of "B2" represented a warbler feeding on the bare, lichen- covered base of a branch. In all, 16 different positions were distinguished”

MacArthur’s Results  MacArthur found that each warbler species divided its time differently among various parts of the tree and can eat a variety of different foods(shown below).

Types of Symbiotic Interactions  Symbiosis: Any relationship in which 2 species live closely together  Ex: Imperial Shrimp and Sea Cucumber (hitches a ride!), Cuckoo Bird (lays eggs in other birds nests!)

Predation  One organism captures and feeds another organism  Ex:Lynx and the Hare “Run bunny, run!”

Mutualism  both species benefit  Ex: Honeyguide and Honeybadger, Acacia Tree and Stinging Ants, Oxpecker and Rhino, Cleaner Fish

Honey Guide and Honey Badger

Acacia and Ants

Oxpecker/ Rhino

Commensalism  one species benefits, the other is neither helped nor harmed  Ex: Sm. Pilot Fish and Shark, Barnacle and Whale, Remora and Turtle, Grouse and Antelope 

Commensalism-Remoras %3Dhowardhall

Barnacles and Humpbacks

Parasitism  one species lives on or in another organism and harms it  Ex: Parasitic Fungi feeding on jungle insects, Tapeworm, Ringworm

Tapeworm (yuk!)

Parasitic Jungle Fungi

Ecological Succession  Series of predictable changes in a community over time  Usually old die out and new replaces  Causes include gradual climate change (global warming?) or sudden disturbance (volcanic eruption, forest fire, humans clearing forests)

Land Succession  Primary Succession: occurs only where no soil exists (possibly from volcanic eruption) Lichens  Mosses  Grasses  Tree Seedlings and Shrubs take root Which species is the “pioneer species”? What makes it successful in rocky terrain? What animals can primary succession attract? Do the animals change with the plant life?

Secondary Succession  Occurs after a disturbance like forest fire where soil already existed  Returns ecosystem to natural state  “Climax Community” term given by ecologists to the stable ecosystem/end product  Do all ecosystems recover after natural disasters or human interactions?

Mt. St. Helens, May 17 th 1980

4 Months After Eruption

4 Years After Eruption

Marine Succession Occurs within an already stable environment! 1.Whale carcass sinks to bottom of ocean and attracts scavengers and decomposers (sharks, hagfish, and tiny amphipods) 2.With most tissue gone, scavengers leave and are replaced with small fish, crabs, and snails 3.With only bone left, it seems barren. BUT, heterotrophic bacteria break down oils in whale bones (which creates energy for chemosynthetic bacteria to begin a whole new food chain!)