Ecosystems

A study of balance and cycles

Key TermsEcosystem

Consists of a biotic community and the abiotic factors that affect itEx – a rain forest, including the animals, plants, soil, rain, sunlight, and temperature

Biotic factorsLiving or once-living organisms in the environmentEx – gorilla, red-eyed tree frog, moss, bacteria

Abiotic factorsAll the non-living, physical features of the environmentEx. sunlight, soil, water, and temperature

Levels of organizationOrganism

A single individual in a populationEx – the oak tree growing in my yard

PopulationAll of the individuals of one species that live in the same area at the same timeEx. – All oak trees in my neighborhood

CommunityPopulations of different species that interact in some wayEx. – Oak trees, squirrels, rabbits, mice, grass, robins, humans

Levels of Organization, cont.

EcosystemCommunities and abiotic factors that affect themEx. Community + soil, light, temperature, etc.

BiosphereAll the ecosystems on Earth

PopulationsPopulation density

The number of organisms in a given areaFormula - # of organisms / areaThe more organisms in a given space, the denser the population

Limiting factorAny biotic or abiotic factor that restricts (limits) the number of individuals in a populationEx. Food supply, # of predators, disease, available shelter

Limiting Factors1. Choose an organism.2. Write five limiting factors for that organism. Be as specific as possible.Ex. Cow

1. Disease - Mad cow disease2. Humans – Humans slaughter cows for food3. Living space – Farms have limited space to house the cows.

RelationshipsSymbiosis

Any close relationship between two or more speciesParasitism, mutualism, and commensalism are all types of symbiosis

ParasitismRelationship that benefits one (the parasite) and does definite harm to the other (host)Ex – Tapeworms benefit by getting nutrients from a dog, but the dog is harmed by the tapeworms

Relationships, cont.Mutualism

A relationship in which both organisms benefitEx Yucca moth and desert yucca plant – moth gets a food source and place for eggs; plant gets its flowers pollinated

CommensalismA relationship in which one organism benefits, but the other is neither harmed nor helped.Ex. Sea anemone and anemone fish – The fish are protected by the sea anemone, but the sea anemone are not affected by the fish

CyclesMany abiotic factors change form as they travel through a cycleMatter is not destroyed, but it changes formExamples

WaterCarbonNitrogen

Water CycleEvaporation – Liquid water found in lakes, oceans, ponds, rivers, etc. evaporates when heat is added. The water takes the gaseous form of water vaporCondensation – Gaseous water vapor condenses when it is cooled and has a solid on which it can condense. The water becomes liquid form.Freezing – Some clouds are high enough in the atmosphere that the water freezes, forming snow or hailPrecipitation –Liquid or solid water collects in clouds, and as more water collects, it becomes heavy enough to fall as rain, snow, or hail

Water Cycle, cont.Run-off – Precipitation hits the ground, is not absorbed, but flows from high elevation to low elevation.Ground water – Precipitation hits the ground and is absorbed into the groundHydration of living organisms – Organisms take in water by drinking, eating, taking water in through roots, and osmosisExcretion – Animals release water in their liquid wastesTranspiration – Plants release water from stomata

Carbon CyclePhotosynthesis – Plants remove carbon dioxide from atmosphere to make carbohydratesRespiration – Other organisms eat the plants. In respiration, they use the energy from the carbohydrates. Carbon dioxide is released as a waste productDecay – Organisms die. The carbon in their decaying remains is returned to the groundCombustion – Carbon is released into the atmosphere when fossil fuels (ex coal and oil) are burned

Nitrogen CycleNitrogen is a gas in our atmosphere. It is also found in organisms in proteins and nucleic acids.Nitrogen gas – In the atmosphere, nitrogen will combine with oxygen in the presence of high temperatures and pressures (lightning) to form nitrogen dioxideNitrogen dioxide combines with rain to form an acid, which falls to the ground with the rain.In the ground, bacteria “fix” nitrogen so that it can be used by plants

Nitrogen Cycle, cont.Plants use nitrogen as a fertilizer. The nitrogen is used to build proteins, which are necessary for growthAnimals eat plants, taking in the proteins containing nitrogen.Animals release wastes, which contain nitrogen. These wastes may be used as fertilizer.Some bacteria convert nitrogen in the soil back into nitrogen gas, which is released into the atmosphere

Energy in EcosystemsEnergy travels through an ecosystem, changing formCommon forms of energy include light, chemical, mechanical, and heat energyOrganisms gain energy by:

Using light or chemical energy to produce their own food (producers)Eating other organisms (consumers)

Producers vs. ConsumersProducers

Plants and some bacteriaPhotosynthesis – use light energy to create carbohydratesChemosynthesis – use chemical energy to create carbohydrates

Found in organisms deep in ocean ridgesConsumers

Eat other organisms for energyOrdered by primary (eat consumers), secondary (eat primary consumers), and tertiary (eat secondary consumers)

Food Chains and Food Webs

Food chains show relationships among a select group of producers and consumers.The chain shows the flow of energy as one organism eats another.Chains are RARELY more than five organisms long

Consumers get only a fraction of the energy contained in the organism they eat.Some energy is used by the original organismMuch energy is lost as heat energy

Example of a Food Chain

Food Chains and Food Webs, Cont.

Food websShow the complexity of consumer/producer relationships in an ecosystemUsed to show that more than one organism may eat a producer or prey AND that an organism may have more than one food sourceTypically, producers are near the bottom of the web and secondary/tertiary consumers are near the topArrows indicate the direction of energy flow

Example of a Food Web

Energy PyramidDiagram used to show producer and consumer relationshipsEmphasizes the relationship of number of prey per organism and the amount of energy that gets transferred from one level (ex. producer) to another level (ex. primary consumer)

Only about 10% of the energy from one level is passed on to the next levelNot all parts of an organism are eatenNot all organisms at one level are eatenSome energy is “lost” as heat energy

Therefore, in an ecosystem, we have MANY producers and primary consumers. As we move up the energy pyramid, the ecosystem can sustain fewer and fewer organisms because there is less and less energy available