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4/20/2020Teacher Background STEMscopesDynamic Nature of EcosystemsTeacher BackgroundDynamic Nature of EcosystemsAn ecosystem is the combination of abiotic and biotic components present in a particular location. Ecosystems are dynamic in nature; their characteristics canvary over time. Changes in either the physical or biological components can alter the populations of many different organisms. These changes are calleddisturbances and can be either natural (volcanic eruption, drought) or man-made (increase in nutrient input by adding fertilizers, extinction of a species by habitatremoval).SpeciesPercent of Population(Pre-Fire)SpeciesPercent of Population(Post-Fire)Human30%Human62%Gray Fox8%Gray Fox1%Domesticated Dog6%Domesticated on9%The re had a notable impact on the populations of various species.For example, California experienced a historic drought in 2014. While drought obviously affects aquatic ecosystems, it also impacts forests. Trees that arestressed by drought become less resistant to diseases such as insect infestations. The lack of water can result in decreasing reproductive success of small preyanimals, which in turn affects predators such as coyotes and bears. Trees killed by insects provide fuel for wild res, removing shelter and killing animals.Depending on the length of the drought and the lifespan of the organisms, effects can be short term or long term. This one disruption to a physical component ofthe ecosystem, the water, led to shifts in all of the ecosystem’s populations.Coyotes are large natural predators present in many habitats. In urban habitats, humans commonly remove coyotes as they can present a danger to domesticanimals. In places where coyotes are absent, the number of smaller predators increases. These smaller predators hunt smaller prey animals, including birds. Whencoyotes are absent, bird species diversity and abundance decrease. Removal of large predators in other ecosystems due to hunting or habitat loss has similarcomplex effects. This scenario demonstrates how the disruption to a biological component, the apex predator, can also lead to population 5603/elements/6920811/2

4/20/2020Teacher Background STEMscopesThe reduction of the tertiary consumer population causes an increase in the secondaryconsumer population. 2020 Accelerate Learning, Inc. All rights /15603/elements/6920812/2

Dynamic Nature of EcosystemsLook at the image of the rain forest to the right. What makes up itsecosystem? Is it just the living things, or do the nonliving thingscount as well?An ecosystem consists of all the living and nonliving things in aparticular area. Let’s look back at the rain forest picture. You cansee a lot of biotic, or living, things, but you can also see abiotic,or nonliving, things. Some biotic examples are the trees, ferns, and moss, while some abioticexamples are the soil and stones. What other organisms would you expect to find in thisecosystem that you cannot see in this picture?It is important to note that an ecosystem’s abiotic factors, such as temperature, wind, and annualprecipitation type and amount, may not be visible.Do ecosystems always stay the same?Because ecosystems consist of living things that can change, it makes sense that the ecosystemitself can change over time. For example, if a certain population experiences a significanttransformation, it will affect the entire ecosystem.Look at the deciduous forest ecosystemdepicted in an energy pyramid on the left. Whatdo you think would happen to the ecosystem ifthe foxes were removed? Would the populationof mice increase or decrease? What about thebald eagles? Would their population increase ordecrease? Without foxes to hunt mice, thepopulation of mice would increase. On the otherhand, without foxes to prey on, the eaglepopulation would begin to decline. Now lookfurther down the energy pyramid. Do you thinkthe absence of the fox would have any impacton the insect population? What about on theplant population? Any change in a biologicalcomponent of an ecosystem can lead to shifts inall its populations.1

Dynamic Nature of EcosystemsEcosystems are not built in a day. Thedynamic, interdependent assemblages ofspecies and environments that make up anecosystem develop over many yearsthrough a process called ecologicalsuccession. Ecosystems have living (biotic)and nonliving (abiotic) components. Thebiotic and abiotic components of anecosystem are interdependent, as eachcomponent changes the nature of the otherinteracting components.What would happen if a city park or a garden were leftunattended, with no mowing, weeding, watering, or any otherhuman interference? At first, weeds would grow and replace thecultivated plants that might have been present. What would thisarea look like after a month? What about after a year or adecade?Ecological SuccessionThe species that make up an ecosystem change over time. In the park pictured above that is nolonger tended, weeds have replaced cultivated plants. Other plants may eventually replace theseweeds. This process is called succession.When the process of succession begins in an area that is bare of living things, it is called primarysuccession. Primary succession is a slow process, because the area in which it is occurring isbarren. The first organisms that are able to grow in such a location, called pioneer species, mustbe able to grow on bare rock.2

Dynamic Nature of EcosystemsEcosystem disruptions may be natural catastrophic events,such as heavy rainfall, floods, droughts, forest fires,tornadoes, and hurricanes. Geologic events such asvolcanic eruptions, tsunamis, and earthquakes also disruptecosystems. Changes to the physical or biologicalcomponents in an ecosystem can directly affect thepopulations of living things. The series of changes theecosystem goes through after the area is disrupted ordamaged is called secondary succession.Disruptions to any physical component of an ecosystem can lead to population shifts as well. Whatdo you think happened to the ecosystems in the pictures below? How do you think these changesaffected the populations in each ecosystem?Once an ecosystem is disturbed, do you think it can ever recover and return to its original balance?Absolutely—ecosystems are amazingly resilient! Consider the pictures above. Both the tornadoand the volcanic explosion have killed many organisms. Over time, the plants and animals willbegin to return. The chaparral plants of Southern California are even adapted to sprout quicklyafter wildfires to help begin the ecosystem’s rebirth.Unfortunately, sometimes people cause disasters as well. In April 2010, the oil rig DeepwaterHorizon exploded, sending millions of gallons of oil into the Gulf of Mexico. This oil spill is the worsthuman-made ecological disaster that has ever occurred. The Gulf Coast ecosystems are stillrecovering from this disaster. How do you think the Gulf Coast ecosystem has changed, and howdo you think it has exemplified resilience?3

Dynamic Nature of EcosystemsTake some time to brainstorm how removing the beetle from the food chain below would affectthe marine ecosystem.Circle what would most likely happen.A.The plant population would increase; the fish population would increase.B.The plant population would decrease; the fish population would increase.C.The plant population would stay the same; the fish population would decrease.D.The plant population would increase; the fish population would decrease.Explain why you selected your answer.4

Dynamic Nature of EcosystemsBelow you will find a food web for a grassland ecosystem. Draw an X through one of theorganisms. Then, in the space below, describe all the changes that would occur to the ecosystem ifthat certain population were to become extinct.5

Dynamic Nature of EcosystemsPre-Reading ActivityForest on FirePredict what will happen to this ecosystem.1

4/21/2020DynamicDynamic Nature of EcosystemsPicture VocabularyCharacterized by constant change, activity, orprogressEcosystemEcosystem DynamicsA system comprising all the biotic and abiotic factorsin an area and all the interactions among themInterrelated changes among the biotic and abioticfactors in an ecosystem over timePopulationResilienceA group of interacting individuals of the samespecies located in the same areaThe ability of an organism, population,community, or ecosystem to persist in the face ofstressful or changing conditions1

4/21/2020CompetitionWhen more than one individual or population in anecosystem relies upon the same limited resources2

ecosystem? Is it just the living things, or do the nonliving things count as well? An ecosystem consists of all the living and nonliving things in a particular area. Let’s look back at the rain forest picture. You can see a lot of biotic, or living, things, but you can also see abiotic