ecological principles lecture 16. ecology = the study of the interaction of organisms with their...
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Ecological PrinciplesEcological Principles
Lecture 16
Ecology = the study of the interaction of organisms with their environments.
It involves understanding biotic and abiotic factors influencing the distribution and abundance of living things.
Biotic Factors• Competitors
• Disease
• Predators
• Food availability
• Habitat availability
• Symbiotic relationships
Abiotic Factors• pH
• Temperature
• Weather conditions
• Water availability
• Chemical composition of environment
• nitrates, phosphates, ammonia, O2, pollution
The word "ecology" coined from Greek word "oikos", which means "house" or "place to live”.
population growth competition between species symbiotic relationships trophic (=feeding) relationships origin of biological diversity interaction with the physical environment
• The entire proportion of the earth that is inhabited by life.
• Includes communities and ecosystems.
The BiosphereThe Biosphere
Forest
TundraSavanna
Desert
A major type of ecological community, determined largely by climate and dominate vegetation.
Population- an interbreeding group of individuals of a single species that occupy the same general areaCommunity-the assemblage of interacting populations that inhabit the same area. Ecosystem- comprised of 1 or more communities and the abiotic environment within an area.
Environmental GradientEnvironmental Gradient
Range of ToleranceRange of Tolerance
Zones of IntoleranceZones of Intolerance
Optimum RangeOptimum Range
Zones of Physiological StressZones of Physiological Stress
Parameters that effect size or density of a population:
Population (N)
Emigration
Immigration
DeathsBirths
Figure 1. The size of a population is determined by a balance between births, immigration, deaths and emigration
Birth EmigrationDeath Immigration
Generation123456789
10
Population Size1248
163264
128256512
Pop
ulat
ion
Siz
e
0
100
200
300
400
500
600
0 1 2 3 4 5 6 7 8 9 10 11 12Number of Generations
Exponential Population Growth
Unlimited resources
k
k
k = carrying capacity
k is affected by:• food production• resource supply• the env.’s ability to
assimilate pollution
exponential
sigmoidal
limiting resources (e.g., food & shelter) production of toxic wastes infectious diseases predation stress emigration
Increasing population density reduces resources and limits pop growth
severe storms and flooding sudden unpredictable severe cold spells earthquakes and volcanoes catastrophic meteorite impacts
Ecological niche = the "role" a species "plays" in the ecosystem.
An organisms use of biotic and abiotic resources in its environment
Contrast the ecological niche with the "habitat" which is the physical environment in which the organism lives.
The ecological niche of a species, therefore includes:
species’ habitat
abiotic & biotic interactions
No two similar species occupy the same niche at the same time.
Extinction of one species
G. F. Gause (1934) tested competitive exclusion principle
Constant food supply
extinction
Resource partitioning: splitting the niche
Sympatric species consume slightly different resources or use resources in slightly different ways
Insect-eating warblers
Character displacement:
two similar species evolve in such a way as to become different from each other by accentuating their initial minor differences
Allopatric vs Sympatric populations
Allopatric populations:
Similar beak morphologies and eat similar sized seeds
Avoids competition
Offset oscillations in the population sizes of the predator and prey
Coevolution of predator and prey
CC66HH1212OO66 + 6O + 6O2 2 6CO 6CO22 + 6H + 6H22O + energyO + energy
Animal cell
6CO6CO22 + 6H + 6H22O + energy O + energy C C66HH1212OO66 + 6O + 6O22
Carbon CycleCARBON CYCLE
Humans affect the carbon Humans affect the carbon cyclecycle Burning fossil fuels moves carbon from the ground to the air.
Cutting forests and burning fields moves carbon from organisms to the air.
Today’s atmospheric carbon dioxide reservoir is the largest in the past 800,000 years.
• The driving force behind climate change
The phosphorus cycleThe phosphorus cycle
Humans affect the Humans affect the phosphorus cyclephosphorus cycle
Mining rocks for fertilizer moves phosphorus from the soil to water systems.
Wastewater discharge also releases phosphorus, which boosts algal growth and causes eutrophication.
May be present in detergents• Consumers should purchase phosphate-free
detergents.
Nitrogen Cycle
Humans affect the nitrogen cycleHumans affect the nitrogen cycle Excess nitrogen leads to hypoxia in coastal areas. Synthetic fertilizers doubled the rate of Earth’s nitrogen
fixation. Burning forests and fossil fuels leads to acid precipitation. Wetland destruction and increased planting of legumes has
increased nitrogen-rich compounds on land and in water. Increased emissions of nitrogen-containing greenhouse
gases Calcium and potassium in soil are washed out by fertilizers. Reduced biodiversity of plants adapted to low-nitrogen
soils. Changed estuaries and coastal ecosystems and fisheries
Human inputs of nitrogen Human inputs of nitrogen into the environmentinto the environment
Fully half of nitrogen entering the environment is of human origin.
Eutrophication
Mississippi River
Eutrophication
runoff
Eutrophication
Gulf of Mexico Dead Zone
2006 Seamap Hypoxia Map
Eutrophication
Fish kills
Biogeochemical Biogeochemical CyclesCycles
Ecological Ecological SuccessionSuccession
The progressive change in the species composition of an ecosystem.
Ecological Ecological SuccessionSuccession
Climax StageClimax Stage
New Bare SubstrateNew Bare Substrate
Colonizing StageColonizing Stage
Successionist StageSuccessionist Stage
PRIMARY SECONDARY
Growth occurs on newly exposed surfaces where no soil exists
Ex. Surfaces of volcanic eruptions
Growth occurring after a disturbance changes a community without removing the soil
2 types of succession
For example, new land created by a volcanic eruption is colonized by various living organisms
Disturbances responsible can include cleared and plowed land, burned woodlands
Mount St. Helens
prior 1980
Mount St. Helens
May 18, 1980
Sep. 24, 1980
Mount St. Helens
Fireweed 1980 after eruption
2004
2012
Hanauma Bay Tuff Ring(shield volcano)
Succession after Volcanic Eruption
What organisms would appear first?
How do organisms arrive, i.e., methods for dispersal?
Volcanic eruption creates sterile environment
Mechanisms of Succession
Facilitation
Inhibition
Tolerance
Early species improve habitat.
Ex. Early marine colonists provide a substrate conducive for settling of later arriving species.
As resources become scarce due to depletion and competition, species capable of tolerating the lowest resource levels will survive.
Competition for space, nutrients and light; allopathic chemicals.
First arrivals take precedence.
r & K Selected Species
Pioneer species- 1st species to colonize a newly disturbed area
r selected
Late successional species
K selected
low competitive abilityshort life spanhigh growth rate
higher maternal investment per offspringlow reproductive output
high reproductive output
slow growth ratelong life spanhigh competitive ability
r & K refer to parameters in logistic growth
equation
Keystone SpeciesKeystone Species
A species whose presence in the community exerts a significant influence on the structure of that community.
Keystone predator hypothesis - predation by certain keystone predators is important in maintaining community diversity.
Paine’s study on Pisaster and blue mussels
Keystone Keystone SpeciesSpeciesKeystone Keystone SpeciesSpeciesAlgal turf farming by the
Pacific Gregory (Stegastes fasciolatus)
Antarctic Ecosystem
krill
Ecological Succession on a Ecological Succession on a Coral ReefCoral Reef
Successional Models and Successional Models and their Impactstheir Impacts
Case 1: No Disturbance (Competitive Exclusion Model)
Case 2: Occasional Strong Disturbance (Intermediate Disturbance Model)
Case 3: Constant Strong Disturbance (Colonial Model)
Case 1: No Disturbance(Competitive Exclusion Model)
• As the reef becomes complex, organisms compete for space.• Dominant organism outcompetes other species.• Occurs in stable environments. • Results in low species diversity.• Highly protected patch reefs within lagoons or protected bays• Deeper water
Case 2: Occasional Strong Disturbance(Intermediate Disturbance Model)
• Storms and hurricanes allow for other species to move in
• Dominant species would not be allowed to reach competitive exclusion
• After each disturbance have a recovery period
• Area of high diversity
Case 3: Constant Strong Disturbance(Colonial Model)
• Constant exposure to disturbance• Shallow environment• High turnover of species• r-selected species
Reef
Case 3
Case 2
Case 1Deep reef slope
Reef slope beneath reef crest
Near reef crest
Ecological Succession on a Coral Ecological Succession on a Coral ReefReef
The Big IslandThe Big Island
Ecological Succession on a Coral Ecological Succession on a Coral ReefReef
Ecological Succession on a Coral Ecological Succession on a Coral ReefReef
Ecological Succession on a Coral Ecological Succession on a Coral ReefReef
Ecological Succession on a Coral Ecological Succession on a Coral ReefReef
Ecological Succession on a Coral Ecological Succession on a Coral ReefReef
Ecological Succession on a Coral Ecological Succession on a Coral ReefReef
Ecological Succession on a Coral Ecological Succession on a Coral ReefReef
Successional Models and their Successional Models and their ImpactsImpacts
Successional Models and their Successional Models and their ImpactsImpacts
The definition of ecology means that:
Ecosystems are often hard to study because:
The "abiotic" part of the environment:
The "Principle of Competitive Exclusion" predicts that:
Questions
A species habitat may be thought of as its "_____" and its niche as its "_____.“
The removal of a keystone species may cause:
A density independent factor that may affect a population is __________.