Goals of This Course

• Understand ecosystem structure and function

• Understand how ecosystems can be disrupted

• Understand local ecological issues

• Understand the basic methods of experimental design and analysis

Ecology and Ecosystems

• Ecology – Study of the interactions of living organisms with one another and with their non-living environment of matter and energy.

Ecology is basically the study of why we find living organisms where we do!

Levels of Ecological Study

• Population – distinct group of individuals of a species that live, interbreed, and interact in the same geographic area.

• Community – includes all of the populations of organisms that live and interact with one another in a given area at a given time.

• Ecosystem – consists of a self-sustaining, self-regulating community of organisms interacting with the physical (abiotic) environment within a defined geographical environment.

• Biosphere – Earth.

• Bayousphere – Research Lab, 303 Gouaux Hall

Levels of Ecological Study

BiosphereBiosphere

Ecosystems

Communities

Populations

Organisms

Universe

Galaxies

Planets

Earth

Biosphere

Landscapes

Ecosystems

Communities

Species

Populations

Individual Organisms

Organ Systems

Organs

Tissues

Cells

Sub cellular Organelles

Molecules

Atoms

Realm of Ecology

One of the main goals of this course is to grasp a detailed understanding of what ecosystem function is and what mechanisms affect ecosystem structure and function.

Timbalier Island 7/2/2005, photo’s by Gary Lafleur

Types of Ecosystems

• Terrestrial– Coastal Chaparral and

Scrub– Coniferous Forest– Desert– Prairie Grassland– Deciduous Forest

• Fresh Water– Lakes– Rivers– Streams

• Marine– Estuaries– Coastlines– Coral Reefs– Deep Ocean

Ecosystem Boundaries?

• It is easy to picture ecosystems as having distinct boundaries.

• The area of transition from one ecosystem to another is considered to be an ecotone.

• Ecotones have a mixture of species from both ecosystems.– A marsh between a freshwater lake and dry

land.– Zone of grasses, shrubs, and scattered small

trees between forests and grasslands.

Where does one ecosystem end and the other begin?

Two examples of ecotones.

Land zone Transition zone Aquatic zone

Numberof species

Species in land zoneSpecies in aquatic zone

Species in transition zone only

Species Overlap in Ecotones

Major Components of Ecosystems• Abiotic - nonliving

– Energy, nutrients, water and air

• Biotic - living– Plants, animals, and microorganisms (biota)

Energy Flow in Ecosystems

Producers

Consumers

Decomposers

Two Laws of Thermodynamics

• First Law: Energy cannot be created or destroyed, but it can be changed from one form to another.

• Second Law: Energy cannot be changed from one form to another without loss of usable energy.

Solarradiation

Energy in = Energy out

Reflected byatmosphere (34%)

UV radiation

Absorbedby ozone

Absorbedby the earth

Visiblelight

Lower Stratosphere(ozone layer)

Troposphere

Heat

Greenhouseeffect

Radiated byatmosphere

as heat (66%)

Earth

Heat radiatedby the earth

First law Second law

When energy transformations occur, energy is neither created nor destroyed (1st Law) but there is always loss of usable energy, usually as heat (2nd Law).

One Way Flow of Energy

Biosphere

Carboncycle

Phosphoruscycle

Nitrogencycle

Watercycle

Oxygencycle

Heat in the environment

Heat Heat Heat

All nutrients are already here.

They are cycled from one organism to another and may have a long abiotic existence.

Some nutrients are lost from ecosystems due to runoff.

While energy has a unidirectional flow through ecosystems, nutrients are cycled.

How Do Ecosystems Gain Lost Nutrients?

• Carbon – Photosynthetic fixation

• Nitrogen – nitrogen fixing bacteria and atmosphere

• Phosphorous – original deposits on land and shallow ocean sediments (artificial fertilizers)

• Oxygen – Photosynthesis

• Water – Precipitation

Heat

Heat Heat

Heat

Heat

Abiotic chemicalsAbiotic chemicals(carbon dioxide,(carbon dioxide,

oxygen, nitrogen,oxygen, nitrogen,minerals)minerals)

ProducersProducers(plants)(plants)

DecomposersDecomposers(bacteria, fungus)(bacteria, fungus)

ConsumersConsumers(herbivores, (herbivores, carnivores)carnivores)

Solarenergy

Biotic Components of Ecosystems:

Producers (autotrophs)

-photosynthesis

Consumers (heterotrophs)

-respiration

Decomposers

Trophic Levels

• Producers (autotroph)

• Primary Consumer (herbivore)

• Secondary Consumer (carnivore)

• Tertiary Consumer

• Omnivore

• Detritivores and Scavengers

• Decomposers

Food Webs (chain) and Energy Flow

Heat Heat Heat Heat

Heat

Heat

Heat

First TrophicLevel

Second TrophicLevel

Third TrophicLevel

Fourth TrophicLevel

Solarenergy

Producers(plants)

Primaryconsumers(herbivores)

Tertiaryconsumers

(top carnivores)

Secondaryconsumers(carnivores)

Detritvores(decomposers and detritus feeders)

Heat

Heat

Heat

Heat

Heat

1010

100100

1,0001,000

10,00010,000Usable energyUsable energy

Available atAvailable atEach tropic levelEach tropic level(in kilocalories)(in kilocalories)

ProducersProducers(phytoplankton)(phytoplankton)

Primaryconsumers

(zooplankton)

Secondaryconsumers

(perch)

Tertiaryconsumers

(human)

Decomposers

Ecological Pyramid

Generally, only about 10% of usable energy is passed on to the next trophic level.

Biomass follows a similar pattern.

Estuaries

Swamps and marshes

Tropical rain forest

Temperate forest

Northern coniferous forest (taiga)

Savanna

Agricultural land

Woodland and shrubland

Temperate grassland

Lakes and streams

Continental shelf

Open ocean

Tundra (arctic and alpine)

Desert scrub

Extreme desert

800 1,600 2,400 3,200 4,000 4,800 5,600 6,400 7,200 8,000 8,800 9,600

Average net primary productivity (kcal/m2/yr)

Net Primary Production (measure of produced energy)

What Factors Limit a Species Abundance and/or Distribution?

Limiting Factor Principle - Too much or too little of any abiotic factor can limit or prevent growth of a population, even if all other factors are at or near the optimum range of tolerance.

Law of Tolerance – The existence, abundance, and distribution of a species in an ecosystem are determined by whether the levels of one or more physical or chemical factors fall within the range tolerated by that species

Tolerance limits – the range of conditions at which a species is able to survive.

A particular species may have a wide tolerance for some variables, but a very narrow tolerance for other variables.

Highly tolerant species can live in a variety of habitats with widely different conditions.

Abiotic Limiting Factors• Temperature

– Law of Tolerance

Po

pu

lati

on

siz

e

Low High Temperature

Zone ofintolerance

Zone ofphysiological stress

Optimum range Zone ofphysiological stress

Zone ofintolerance

Noorganisms

Feworganisms

Lower limitof tolerance

Abundance of organismsFew

organismsNo

organisms

Upper limitof tolerance

If temperature is optimum, but dissolved oxygen is too low, there will be no fish!

Select Key Factors Affecting Ecosystems

• Terrestrial– Sunlight– Temperature– Precipitation– Wind– Latitude (distance from

equator)– Altitude (distance

above sea level)– Fire Frequency– Soil

• Aquatic– Light Penetration– Water Currents– Dissolved Oxygen– Salinity– Dissolved Nutrient

Concentrations (especially N and P)

– Suspended Solids

What is Ecosystem Structure

?

What is Ecosystem Function

?

Local Issues You Should UnderstandAssignment 1

1. Subsidence

2. Global Warming

3. Sea Level Rise

4. Wetland Loss

5. Invasive Species

6. Eutrophication

7. Human Population Growth

Pick one of these subjects and write a two page (12 pt font double spaced) synopsis that explains how that issue may affect Louisiana.

Scientific Method

• Observation

• Hypothesis

• Experiment

• Conclusion

• Theory

What is the question?Designed to answer the question?Correct interpretation?

Experimental Design

• Will this design answer my question?– Treatment / Control – what is the question?

– Randomization – assignment of treatments to experimental units so as to reduce bias

• Bias – a unidirectional shift in error

– Replication – assigning of more than one experimental unit to a treatment combination

• What is the experimental unit?

Experimental Unit

• The basic unit of study used for replication

• Examples…..