CHAPTER 6 ECOSYSTEM BALANCE

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

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

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

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

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.

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

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

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

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                                                          

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)

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

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)

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.

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

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

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)

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

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

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