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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?????