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

http://www.fotosearch.com/ATB717/vus118/

Commensalism-Remoras

http://www.oceanfootage.com/stockfootage/Sea_Turtle/owner%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) LichensMossesGrassesTree 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? http://bcs.whfreeman.com/thelifewire/content/chp55/55020.html

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 17th 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!)