1. CHAPTER 6
ECOSYSTEM
BALANCE

2. Relationships in the Ecosystem
All organisms need food to survive
Consumers that must actively hunt for other organisms as a source of food are predators
The organisms hunted for food are called prey
Ex: the lynx and the snowshoe hare

3. Symbiosis
Symbiosis - two species live closely together in an ecosystem. From ancient Greek – syn (with) biosis (living)
Can take place between plant, animal, fungi, or any combination
Ex: crocodile and croc-bird, sucker fish and the shark, us and the Earth

4. Ecosystem Relationships
Parasitisim – one organism feeds on the tissues or body fluids of another, called the host. Parasites may or may not cause harm to their hosts
Ex: West Nile Disease is a virus that is passed from infected bird to other birds, mammals and even humans by the bite of a mosquito.
The mosquito is also known as a vector because it needs blood meals to survive and reproduce

5. Parasitism
One organism (parasite) feeds directly from another organism (host).
The parasite benefits and the host is harmed (sometimes lethally).
Ex: tapeworm, hookworm, tick, bed bug

6. Commensalism
A relationship that benefits one organism and neither helps nor hurts the other (neutral).
Comes from the Latin com mensa “to share a table”
Ex: cattle egret feeds on insects stirred up as cattle or horses graze the grass for food.

7. Mutualism
A relationship where both organisms help each other. Both organisms benefit in a “win-win relationship”.
Ex: legumes and nitrogen-fixing bacteria; pollinating plants by bees and butterflies, clownfish and the sea anenome

8. Ecological Succession
The Earth is made of rock
Lichens (fungus and algae) can live on bare rock
Lichens secrete acid which breaks down the rock into soil
Lichens are known as a pioneer community

9. Ecological Succession
Lichens are replaced by
grasses
Grasses further enrich the
soil allowing shrubs to grow
Pine trees replace shrubs
Deciduous trees
(oaks, maples, elms)
replace pines
Climax community – a community that does not experience additional
succession

11. Secondary Succession
Secondary succession — occurs when a community has been cleared by a major disturbance (fires, storms, human activity) that doesn’t destroy the soil
                                                         

12. Other Forms of Succession
Aquatic Succession
Aquatic habitats also experience succession
Water gradually gain nutrients and supports reeds and other water plants
Organic matter (sediment) collects on the lake floor
More and more water plants cover the surface of the lake
When the lake fills in with sediment is becomes a marsh
Land plants gradually replace the marsh plants to change the community into a fertile meadow
Island Succession
Island succession occurs much like it does on land
Islands appear quickly after volcanic eruptions
Any organisms found on an island usually arrive by water, wind or other organisms
Most islands have large bird populations
Organisms can adapt to fill many niches because there is no competition for resources (Galapagos finches)

13. Balance in the Ecosystem
All elements in an ecosystem are connected to each other (abiotic and biotic factors)
All processes in the ecosystem link together in a complex arrangement (food web)
All natural ecosystems are STABLE – maintain a state of balance or equlibrium
Systems that do not maintain equilibrium do not survive

14. Ecosystem Balance
Major disruptions cause major changes in an ecosystem
A new ecosystem will develop to replace the old one that was destroyed.
Evolution of organisms is part of this development
Organisms MUST adapt to majors changes or die out (face extinction)

15. Ecosystem Balance
Chaos Theory – mathematical explanation of the effect small and large changes have on a particular ecosystem.
Analyzing a complex system with both abiotic and biotic factors and multiple organisms can very very difficult.
Hard to predict what the effect even one small change will have in the furture of an ecosystem.

16. BIOMES
Biome – A major type of ecosystem with distinctive temperature range, rainfall and organisms
Two kinds of biomes: terrestrial (land) and aquatic (water)
Terrestrial biomes are classified by average temperatures and precipitation
Aquatic biomes are classified by water depth, nutrient levels and location relative to land

17. Terrestrial Biomes Divided into 8 major biomes
Desert and Tundra – very little water, small amount of biomass

18. Terrestrial Biomes Forest – 75% of the Earth’s biomass
3 forest biomes:
Coniferous (pine)
Deciduous (trees that lose leaves)
Rain (most water, 6% of all biomass)

19. Terrestrial Biomes Grasslands – 22% of Earth’s land surface
8% of Earth’s biomass
Steppe – northern
Prairie - central
Savanna - southern

20. TERRESTRIAL BIOMES Tundra Coniferous Forrest Deciduous Forrest
Very little water
Short shallow root plants
Permafrost
Coniferous Forrest
Pine forest
Moderate precipitation
Higher elevations
Deciduous Forrest
Hardwood trees that lose their leaves
Sufficient precipitation
Rain Forrest
Most precipitation
Most plant and animal species on Earth
Steppe
Northern grasslands
Cooler temperatures
Prairie
Central portions of many continents
Large areas of grasses
Savanna
Warmer, southern grasslands
Located near or below the equator
Desert
Poor soil or sand
Harsh temperatures
Classified by elevation

21. Terrestrial Biomes Fact Sheet
Tundra
Coniferous Forrest
Deciduous Forrest
Rain Forrest
Steppe
Prairie
Savanna
Desert