lecture 240 ecology - fall 2004people.cst.cmich.edu/gehri1tm/bio 240/bio 240 - week 2.pdf2 major...
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Ecology What is it? Ecology
• Hierarchy of Organization- Individual- Population - # of individuals in given area- Community – all biota in an area- Ecosystem – all biota & abiotic factors- Landscape – multiple ecosystems over
large area- Biosphere – all life on Earth
Ecology
Autecology: study interrelations of individuals with environment
Synecology: study of communities
Basic Scientific Principles
• Law of Conservation of Matter
• 1st Law of Thermodynamics (Energy)
Matter cannot be created nor destroyed, rather it can only be transformed
Energy cannot be created nor destroyed, rather it can only be converted in form
Basic Scientific Principles
• 2nd Law of ThermodynamicsWhen converting energy, always lose some energy as heat
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Major Ecosystem Processes
1) Energy Flow = energy moves through system
2) Nutrient Cycling = chemical elements recycled in system
Energy Flow
• Solar energy – primary energy source (fig 3.5, p. 42)
Of incoming solar radiation:66% absorbed 34% reflected (albedo)
Solar Energy
• Of solar radiation absorbed:- ~22% water cycle- nearly all transform to heat &
radiatesemissivity: relative ability of Earth to
release energy (e.g., radiate heat into space; link to global warming)
Solar Energy • Tiny amount of solar energy into
photosynthesis (< 0.1%)photosynthesis (PNS): use solar energy to convert CO2 & H2O into sugar; by-product = O2primary production: all organic matter resulting from PNS; raw material for other organisms (gross production vs. net production)
Energy Flow in Communities
food chain: sequence of organisms linked by energy & nutrient flow
trophic level: feeding level/position of organism in food chain
Trophic Levels Producer: (autotrophs) anchor of chain;
produce all organic matter for other organisms
Primary consumer: directly consume producers = herbivores
Heterotrophs (consumers)
Secondary consumer: consume herbivores Tertiary & Quaternary consumers: consume
secondary & tertiary consumers, respectively
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Trophic Levels Decomposers: (detritus feeder) consume
and convert dead material for use by producers
Food Webs food web: interconnected food chains; all
trophic interactions in community
Human Impacts Ecosystem simplification: elimination of
species from food webs via human alterations to land
Example: vertebrate communities in ag. landscapes
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Energy Flow Between Trophic Levels
Does 100% of energy transfer from 1 trophic level to another?
No. Remember 2nd Law of Thermodyn.
Range 5-20% transference (usually ~10%)Graphical representation of energy
transference in food web = energypyramid
Energy Flow Between Trophic Levels
Why such low efficiency?
Three Reasons:
1) Escape behavior/protective coloration/unavailable material
2) Indigestible material3) Cellular respiration
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Bioaccumulation = Biomagnification
Nutrient Cycles
What does the Law of Conservation of Matter state?
• circular flow of chemicals = recycling• Inputs & relationship to energy flow?• Water, Carbon (C), Nitrogen (N),
Phosphorus (P), Sulfur (S)
Carbon Cycle • Carbon = building block of life• Reservoirs = atmosphere, ocean,
organisms• High rate of exchange in/out reserves
• Any relation to global warming?
Nitrogen Fixation Types
1) atmospheric fixation via lightening or sunlight; NO3 as precipitation (ppt)2) biological fixation* via soil & water bacteria (blue-green algae); NH3; legumes & root nodules Water Quality & NitratesSoil Condition & Fertilizers
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Phosphorus Cycle
• Water Quality & Phosphorus
• Eutrophication: increase in nutrient content of lakes
Some Ecological Principles Individual• Law of Tolerance: organisms can
tolerate a range of conditions beyond which they die
• e.g., temperature, nutrients • age-dependent, DNA
Where does habitat fit? Habitat: home; area having necessary
resources (food, water, cover) and environmental conditions (temp., ppt) that allows organism to live & reproduce
Your habitat = ?????What if habitat is drastically changed or
destroyed?• Move, Adapt, or Die
Properties of Communities
1) Species Richness = # species in a comm.2) Species Evenness = relative abundance of
different species3) Species Diversity = richness & evenness
e.g., Four species (A,B,C,D) in 2 different communities
Comm 1 – 25A 25B 25C 25DComm 2 – 97A 1B 1C 1D
What Happens in a Community?
1) Competition: individuals contest over a resource (food, space, water, mates…) –major factor determining structure
Types of CompetitionA) Interspecific: competition between
different species, e.g., blue jay & chickadee compete for sunflower seed at feeder
B) Intraspecific: competition within the same species, e.g., 2 male bobcats compete for space
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Principle of Competitive Exclusion (Gause’s experiments)• Two species which compete for same
resource cannot coexist in same place at same time
• Implications = different locations or different times
• Relates directly to niche concept
Niche Concept
Niche: functional role (“occupation”) & position (spatial & temporal) of a species in its community
• Principle of Competitive Exclusion = 2 species cannot occupy the same niche
What Happens in a Community? (cont.)
2) Predation: one species consumes another species
Some Ecological Principles Community• Biological Succession: temporal
sequence of one community replacing another; predictable
• Primary vs. Secondary
Biomes Terrestrial community of common climate
& unique species assemblages1) Tundra – permafrost2) Boreal Forest 3) Deciduous Forest4) Tropical Rain Forest5) Tropical Savannah6) Grassland7) Desert
rNdtdN =
−=
KNrN
dtdN 1
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Density-dependent Effects
Who Cares?
Why bother discussing these models?Metapopulations & Source-sink Populatons
highlight the importance of:• habitat & landscape fragmentation• connectivity between isolated
populations• genetic diversity
Habitat Fragmentation • Process of breaking contiguous unit into
smaller pieces; area & distance components
• Leads to:< remnant patch size> edge:interior ratios> patch isolation< connectivity
• Community & Ecosystem processes altered
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Habitat Fragmentation • First-Order Effects: fragmentation leads
to change in a species’ abundance and/or distribution
• Higher-Order Effects: fragmentation indirectly leads to change in a species abundance and/or distribution via altered species interactions
Habitat Fragmentation • area-sensitive species: species that
require minimum patch size for daily life requirements
• Edge effects: influence of factors from outside of a patch
Edge Effects • Habitat surrounding a patch can:
- change abiotic conditions; e.g., temp.- change biotic interactions, e.g.,
predation Example of nest predation = edge effect of
approximately 50 m into forest patch
Conservation Implications • All habitats are “islands”• The “internal external threat”• Develop & manage reserve as
landscapes/ecosystems linked by movement of species (metapop. concepts)
• Develop strategies for countering edge effects……predator control?????
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