2Ecosystem Balance 6.1 Relationships in the Ecosystem 6.2 Ecological Succession6.3 Stability in the Ecosystem6.4 Land Biomes
36.1 Relationships in the Ecosystem ObjectivesExplain the relationship between the population sizes of predator and prey.Define symbiosis and describe several symbiotic relationships.
4Relationships in the Ecosystem A complex web of relationships exist among all the species in an ecosystem.Scientists study these relationships by:Studying how two populations interact with one another.Expanding the knowledge they have gained to other parts of the ecosystem.
5Predator and PreyOne of the relationships ecologists study is that of predator and prey.Define Predator.Define PreyExamples
10SymbiosisSymbiosis-a relationship in which two species live closely togetherThree types:Parasitism-one is helped and the other is harmed (typically)Commensalism- one organism benefits and the other is neither helped or harmedExamplesMutualism-both organism benefit
15Objectives Contrast primary and secondary succession. Describe the sequence of ecological succession in a lake and on an island.
16Ecological Succession Organisms affect their environmentExample: Plants SoilChanges are not always beneficialOld niches are replaced by new niches.Other forces can cause change in the environment.Example: Forest Fire
17Ecological Succession As environment change the communities living in that environment change as well.In many cases different communities follow one another in a definite pattern, this is called succession.
18Volcano EruptionA volcano erupts leaving the land covered in bare black rock…it is lifeless.Does it stay this way?
19Volcano Eruption (cont) Almost immediately organisms begin to inhabit the area.
20Primary Succession Define Primary Succesion Examples: Cooled lava fields and exposed rock from retreating glaciers.
21Primary Succession Primary succession is an orderly process. Follows the same general pattern in most ecosystems.
22Step 1Colonization by new organisms and formation of soil from exposed rock.On land this is done by lichens.Define lichens.Lichens can live on bare rock.
23Step 1 (cont)Lichens secret acids that break down the rock and form organic material by photosynthesis.Weathering also breaks down rocks.Soil is formed by the actions of the lichens and weathering.
24Pioneer Community Lichen Community First community to colonize the area.
25Step 2Once soil is formed, grasses and other small plants begin to grow.Root growth and accumulation of dead leaves Soil formationPlants grow dense lichen disappear
26Grass CommunitySurvives for many generations and makes the soil deeper and more fertile.Soil is deep enough Growth of nonwoody plants with deep roots (Heath Mat).These plants are taller and shade out the grasses.Since the grass/shrub community is not diverse a small disturbance may cause drastic change.
27Pines and other tressPines or other trees with shallow roots are next.Trees shade out the heath mat.
28Broadleaf and Hardwood Trees As the soil deepens even further broadleaf and hardwood trees take over.Hardwood forest in the final stage of succession in many areas.
29Climax Community A community that does not undergo further succession. Climax communities are usually highly diverse and can often survive even severe local disturbances.
31Primary SuccessionOnly occurs on freshly exposed rock or in places where a severe disturbance has occurred.However most disturbances are not this drastic.
32Secondary SuccessionA fire may kill many plants but leave the soil in place.Living things can quickly colonize these types of areas.Define Secondary Succession.Examples: Storms, Fires and human activity
37Aquatic Succession Newly formed mountain lake. Low nutrient levelsSupports few organisms.Reeds and other aquatic plants.Organic matter builds up and lake fills with sediment.Nutrient rich waterIncrease in wildlifeWater plants cover the surface.Lake fills with sediment MarshLand plants begin to colonizeFinally Fertile Meadow (possibly a forest)
39Island Succession Similar to succession on the continents. Any organisms found on an island must have ancestors that were:Carried by waterCarried by windCarried by other organismsMany islands have large bird populations.
40Island Succession There are many unfilled niches on islands. Organisms can evolve to fit many niches.When a population of organisms adapted to their new niches new species are formed.Example: Figure 6.9 p. 95
41ReviewHow does primary and secondary succession differ from each other?What is a climax community?What is a pioneer community?Describe the sequence of ecological succession in a lake and on an island.
43Objectives Explain the concept of ecosystem stability. Characterize the effects of disturbances on the ecosystem
44Stability is a measure… …of how easily an ecosystem is affected by a disturbance.…how quickly it returns to its original condition after a disturbance.Conditions include: biotic and abiotic factors, patterns of energy flow and nutrient cycling.
45More stable ecosystem Will return steady pattern of energy flow Experience fewer food web changes.Fewer evolutionary changesFewer changes in the abiotic environment.
46Stability in the Ecosystem Determined by the complexity of food webManages the system’s energy flow and nutrient cycles.More connections=stabilityImpact of disturbance is less.
47Equilibrium State of balance Changes counteract other changes. Weather cooling is counteracted by the evolutionary adaptation to cold weather.Disturbed ecosystem returns to a state of equilibrium (balance).
48Ecosystem FunctionScientist do not understand every detail of how even simple ecosystems function.They do understand that a change in one part of triggers a change in another.Scientists are trying to apply the chaos theory.
49Chaos Theory A type of mathematics Suggests that ecosystem may be sensitive to even small changesThe beginning state of an ecosystem is crucial to its later development.
50Species Extinction Species are becoming extinct at an alarming rate. Fastest since the extinction of dinosaurs.Possible causes:Human GrowthHabitat destructionIntroduction of foreign speciesPollution of fresh water
51ThoughtIt is difficult for scientists to predict the long-term effects of humans on the biosphere.And for them to predict the ability of the biosphere to support human population.
52Review What makes an ecosystem stable? What happens to a stable ecosystem when a disturbance occurs?What happens to a ecosystem that is unstable when a disturbance occurs?
54ObjectivesExplain the concept of the biome, and name the eight major land biomes.Name an area in which each type is located.
55Biomes Earth is very large and diverse Environments range from the ice of Antarctica to the heat and rain of the Amazon.Difference in temperature and rainfall create a vast array of conditions.Life has adapted to almost all of these conditions.
56BiomesDefinition-major type of ecosystem with distinctive temperature, rainfall and organisms.Either terrestrial or aquatic.
57BiomesBiome is the largest general category used to classify ecosystemsConditions may vary from place to placeSmaller ecosystems within a biome may have different habitats with different conditions and organisms.Every habitat on Earth is different.Term Biome is useful when discussion related habitats.
58Aquatic BiomesDetermined by:Water depthNutrientsNearness to land
59Terrestrial Biomes Determined by: Average temperature Amount of precipitation8 major types of land biomesDesertTundraConiferous forestDeciduous forestRain forestSteppePrairieSavanna
60Desert Low humidity High summer temperatures Low annual rainfall Supports only a small amount of biomassDeserts cover 25% of Earth’s land surfaceDeserts contain only 1% of Earth’s biomassPlant life is scarce in a desert due to lack of water
64Forest Biomes Contains 75% of Earth’s Biomass Three types: Coniferous forest- containing conifers.Deciduous forest – containing deciduous trees.Rain forest –dense canopy of evergreen, broadleaf trees that receives at least 200 cm of rain each year.
68Rain forest Covers only 6% of Earth’s land surface. Contains more than 50% of all Earth’s biomass.Most diverse biome.Destruction of the rain forest is a HUGE environmental problem
69Grasslands Cover 22% of Earth’s land surface Contain 8% of Earth’s biomass.Grasslands receive less precipitation than do forests and may have long dry seasons.May experience frequent firesHome to large herds of migrating herbivoresThree types:SteppePrairieSavanna
70Steppe Grassland Biome Receives less than 50cm of rain per year Characterized by short bunchgrasses.