Chapter 4 Ecosystems: How They Change. Population Dynamics: Population Growth curves (p83): ...
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Transcript of Chapter 4 Ecosystems: How They Change. Population Dynamics: Population Growth curves (p83): ...
Chapter 4Chapter 4Ecosystems: Ecosystems:
How They ChangeHow They Change
Population Dynamics:Population Dynamics:Population Growth curves (p83):Population Growth curves (p83):
J-curves, also known as J-curves, also known as exponential growth, exponential growth, could result in repeated could result in repeated J-curves, S-curve J-curves, S-curve equilibrium or total equilibrium or total devastation.devastation.
S-curves, also known as S-curves, also known as logistical growth, logistical growth, represent populations in represent populations in equilibrium.equilibrium.
Population Growth terms (pp84-86):Population Growth terms (pp84-86): Biotic potentialBiotic potential: The maximum reproductive capacity of an : The maximum reproductive capacity of an
organism under optimum environmental conditions.organism under optimum environmental conditions. RecruitmentRecruitment: The success rate of young reaching a breeding : The success rate of young reaching a breeding
ageage Population explosionPopulation explosion: exponential increase of a population: exponential increase of a population Environmental resistanceEnvironmental resistance: factors that inhibit population : factors that inhibit population
growthgrowth Replacement levelReplacement level: The fertility rate that sustains a stable : The fertility rate that sustains a stable
populationpopulation Carrying capacityCarrying capacity: maximum population that an ecosystem : maximum population that an ecosystem
can support without degradationcan support without degradation Dynamic balanceDynamic balance: the addition of births and subtraction of : the addition of births and subtraction of
deaths continue where a population fluctuates around a deaths continue where a population fluctuates around a medianmedian
Population densityPopulation density: # of individuals per unit area: # of individuals per unit area Critical numberCritical number: minimum # below which the survival and : minimum # below which the survival and
recovery of a species is in dangerrecovery of a species is in danger
FactorsFactors that affect population growth that affect population growth
Density DependentDensity Dependent
Food supplyFood supply
CompetitionCompetition
PredationPredation
DiseaseDisease
Resource availabilityResource availability
Density IndependentDensity Independent
FiresFires
TornadoesTornadoes
DraughtDraught
Habitat disturbanceHabitat disturbance
Extreme Extreme temperaturestemperatures
FloodsFloods
Mechanisms of Mechanisms of Population EquilibriumPopulation Equilibrium
1.1. Predation –prey relationshipsPredation –prey relationships Predation on animalsPredation on animals ParasitesParasites Herbivores eating plantsHerbivores eating plants
2.2. CompetitionCompetition Between plant species can be interspecific if niches Between plant species can be interspecific if niches
overlap creating adaptations (Examples: riparian overlap creating adaptations (Examples: riparian forests, different grasses, mutualistic epiphytes, forests, different grasses, mutualistic epiphytes, balanced herbivory of the rainforests)balanced herbivory of the rainforests)
Territoriality is a result of intraspecific competition Territoriality is a result of intraspecific competition (Ex: wolves staking out territory)(Ex: wolves staking out territory)
Mechanisms of Mechanisms of Population equilibrium (cont)Population equilibrium (cont)
3. Introduced Species (p 94 and 95) alter 3. Introduced Species (p 94 and 95) alter habitats, endanger species, deplete habitats, endanger species, deplete resources, spread disease, and alter resources, spread disease, and alter food websfood webs
Evolution as a Force of ChangeEvolution as a Force of Change
Adaptation through natural selectionAdaptation through natural selection Adaptation to the environmentAdaptation to the environment Limits of change: migration, extinction, Limits of change: migration, extinction,
survival adaptationssurvival adaptations Evolution of a species: Darwin’s finchesEvolution of a species: Darwin’s finches
Drifting continentsDrifting continents
Disturbance and SuccessionDisturbance and Succession
Equilibrium Theory is challenged by:Equilibrium Theory is challenged by: Ecological succession occurs until a climax Ecological succession occurs until a climax
ecosystem is reached (if at all)ecosystem is reached (if at all) Primary succession (p 96)Primary succession (p 96) Secondary succession (p 96)Secondary succession (p 96) Aquatic succession (p97)Aquatic succession (p97) Climate changeClimate change
Disturbance and resilienceDisturbance and resilience Some species are eliminated, changing an ecosystemSome species are eliminated, changing an ecosystem Fires, drought, wind, and storms are often necessary to Fires, drought, wind, and storms are often necessary to
achieve a climax ecosystemachieve a climax ecosystem
Primary and Secondary Primary and Secondary SuccessionSuccession
More SuccessionMore Succession
BiodiversityBiodiversity
The most stable of ecosystems maintain The most stable of ecosystems maintain population equilibrium through diversity.population equilibrium through diversity.
Implications for humansImplications for humans
Adaptive management has been adopted Adaptive management has been adopted by federal agencies to assure by federal agencies to assure sustainability of ecosystemssustainability of ecosystems Plan for the long term and unexpected eventsPlan for the long term and unexpected events Avoid land uses that deplete resourcesAvoid land uses that deplete resources Minimize introduction of foreign speciesMinimize introduction of foreign species
5 Principles of 5 Principles of Ecosystem SustainabilityEcosystem Sustainability
1.1. For sustainability, ecosystems use sunlight For sustainability, ecosystems use sunlight as their source of energy.as their source of energy.
2.2. Ecosystems dispose of wastes and replenish Ecosystems dispose of wastes and replenish nutrients by recycling all elements.nutrients by recycling all elements.
3.3. The size of consumer populations is The size of consumer populations is maintained such that overgrazing and other maintained such that overgrazing and other forms of overuse do not occur.forms of overuse do not occur.
4.4. Ecosystems show resilience when subject to Ecosystems show resilience when subject to disturbance.disturbance.
5.5. Ecosystems depend on biodiversity.Ecosystems depend on biodiversity.