ecology lec11

7/31/2019 Ecology Lec11

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ECOLOGY


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Prof. M M Ghangrekar Department Civil Engineering,(Co-ordinator)

Prof. A K GuptaDepartment of Civil Engineering

Prof. Mihir K. DashCentre for Oceans, Rivers, Atmosphere and Land Sciences

Prof. Abhijit MukherjeeDepartment of Geology and Geophysics


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What is Ecology?

The term ecology or oekologie was coined by the German biologist ErnstHaeckel in 1866, when he defined it as " the comprehensive science of the

relationship of the organism to the environment ." Haeckel did not elaborate on theconcept, and the first significant textbook on the subject ( in 1895 ) (together with the firstuniversity course) was written by the Danish botanist, Eugenius Warming . For thisearly work, Warming is often identified as the founder of ecology .

Scope of EcologyEcology is the scientific study of the distribution andabundance of life and the interactions between organismsand their environment.

a. Interactions determine distribution and abundance of organisms.

b. Two main themes in ecology are:- Where do organisms live? & Why?- How many organisms are present? & Why?


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c. Ecology was historically an observational science, often

descriptive natural history.

d. An organism s environment has both abiotic and bioticcomponents.

- Abiotic components are nonliving chemical and physicalfactors such as temperature, light, water, and nutrients.

- Biotic components are living factors such as other

organisms.


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An ecosystem has abiotic and biotic components:

ABIOTIC components :

Solar energy provides practically all the

energy for ecosystems.

Inorganic substances , e.g., sulfur, boron,tend to cycle through ecosystems.

Organic compounds , such as proteins,carbohydrates, lipids, and other complexmolecules, form a link between biotic and

abiotic components of the system.


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BIOTIC components: The biotic components of an ecosystem can

be classified according to their mode of energyacquisition .

In this type of classification, there are:

Autotrophs and

Heterotrophs


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Autotrophs (=self-nourishing) are calledprimary producers .

Photoautotrophs fix energy from the sunand store it in complex organiccompounds

(= green plants, algae, some bacteria)

Photo-autotrophssimpleinorganic

compounds

complexorganic

compounds

light

6CO2(gas) + 6H2O(liquid) --------------------------- -----C6H12O6(solid) + 6O2(gas)(Light & chlorophyll)

(-1250 kJ/mol

glucose)

6x(-393.5 kJ/molCO2)

6x(-285.8 kJ/molH2O liquid) +2826 kJ/mol glucose


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Chemoautotrophs (chemosynthesizers) are bacteria

that oxidize reduced inorganic substances (typically sulfur and ammonia compounds) and produce complex organiccompounds.

complexorganiccompounds

oxygen

Chemoautotrophs

chemoautotrophsreducedinorganiccompounds

Hydrogen sulfide chemosynthesis :CO 2 + O 2 + 4H 2S CH 2O + 4S + 3H 2O

(purple sulfur bacteria)


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The Biotic Components of Ecosystems

Producers(autotrophs)

- PhotosynthesisConsumers(heterotrophs)

- Aerobicrespiration

Decomposers


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Heterotrophs (=other-nourishing) cannotproduce their own food directly from

sunlight+ inorganic compounds. Theyrequire energy previously stored incomplex molecules.

heterotrophscomplexorganiccompounds

heat

simpleinorganiccompounds

Heterotrophs can be grouped as:consumers

decomposers


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2. Ecology and evolutionary biology are closely related sciences

Events that occur in the framework of ecological time (minutes, days,years) translate into effects over evolutionary time (decades, millennia).

Example: Hawks feeding on mice impact mouse population and mayeventually lead to selection for mice with fur as camouflage.

3. Ecological research scale ranges from individuals to the biosphere

a. Organismal ecology is concerned about the way in which an individualinteracts with its environment.

b. Population ecology is the study of a group of individuals of the samespecies.

c. Community ecology deals with all interacting species within aparticular area.


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d. An ecosystem consists of all abiotic factors plus allorganisms that exist in a certain area Ecosystem ecology .

Landscape ecology- interactions among ecosystems.

e. The biosphere is the global ecosystem. Global climateresearch is an example of ecology at the biosphere scale.

Organis

m

biosphere ecosystem

Community ecology Population ecology


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II. Factors affecting the distribution of organisms

- Biogeography is the study of past and present distributionof individual species.

Neotropic or Neotropical zone is one of the eight terrestrial ecozones. This ecozoneincludes South and Central America, the Mexican lowlands, the Caribbean islands, and

southern Florida , because these regions share a large number of plant and animalgroups.

The Nearctic ecozone covers most of North America, including Greenlandand the highlands of Mexico

Physically, the Palearctic is the largestecozone. It includes the terrestrialecoregions of Europe, Asia north of theHimalaya foothills, northern Africa, and thenorthern and central parts of the ArabianPeninsula

The Orient means "theEast." It is a traditionaldesignation for anything that belongsto the Eastern world or the Far East, inrelation to Europe
http://en.wikipedia.org/wiki/Floridahttp://en.wikipedia.org/wiki/Florida


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A. Species dispersal contributes to the distribution oforganisms

Dispersal refers to the process of distribution ofindividuals within geographic population boundaries.

Question: Is the distribution of a species limited by

dispersal, i.e. by movement of the organisms?

Answer can be obtained by transplant experiments .

If the transplant is successful, then the organisms justhaven t reached the target area.

If the transplant is not successful, then other factorslimit the distribution of the organisms, such ascompetitors, lack of a food source, etc.


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B. Behavior and habitat selection contribute to thedistribution of organisms

1. Organisms may not occupy all potentially suitablehabitat. Why? a. Evolution doesn t lead to perfect organisms. b. Evolution is an ongoing process. Environments

change, but it takes a while for organisms to respond.

C. Biotic factors affect distribution

1. Organisms required for potential community members tocolonize may be lacking.

- Pollinators, prey, predators that limit competition


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D. Abiotic factors affect distribution

1. Abiotic factors of interest include:

- Temperature (range from 0 to 45 C)

- Water

- Sunlight

- Wind (increases heat & water loss)

- Rocks and soil


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Fig. 50.13 Copyright 2002 Pearson Education, Inc., publishing as Benjamin Cummings


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Local and seasonal effects on climate. Bodies of water and topographic features such

as mountain ranges can affect local climates. Ocean currents can influence climate in

coastal areas. Mountains affect rainfall greatly.

Copyright 2002 Pearson Education, Inc., publishing as Benjamin Cummings


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Lake stratification and mixing alters oxygen and nutrientlevels. Dependent on temperature changes and effect onwater density.


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THE RULES OF ECOLOGY

F. A. BAZZAZ:

1. Everything is connected to everything else.

2. Everything must go somewhere.

3. There is no such thing as a free lunch.

To understand any system you must understand the nextlarger system.


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What sustains life on earth?

The one-way flow of high-quality energy

The cycling of matter or nutrients

Gravity Allows the planet to hold onto its atmosphere Causes the downward movement of nutrients


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H d h i lif h?


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How does the sun sustain life on earth?


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The Laws of ThermodynamicsEnergy flow is a one-directional process.

sun ---> heat (longer wavelengths)

FIRST LAW of THERMODYNAMICS:

Energy can be converted from one form to another, butcannot be created or destroyed.


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Laws Governing Energy Changes

Second Law of Thermodynamics

In every transformation, some energy isconverted to heat (lower quality)

You cannot break even in terms of energy quality


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Energy flow

Simplistically:

This pattern of energy flow among different organisms is

the TROPHIC STRUCTURE of an ecosystem.

heat

Producers Consumers

Decomposers

heat


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Connections: Matter and Energy Laws andEnvironmental Problems

High-throughput (waste) economy

Matter-recycling economy

Low-throughputeconomy

E F i


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Ecosystem Function

#1. Energy flow in an ecosystem is represented bya food web.

The amount of energy available to the organisms at eachtrophic level decreases as one moves up the food chainsince

energy is lost as heat and organisms use energy to sustain themselves Remember the laws of energy?


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Because the amount of energy decreases at eachsuccessive trophic level, the number of organisms alsodecreases

Only approximately 10% of the energy is transferred to thenext trophic level.

So, are there more producers or consumers on Earth?


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Energy and biomass pyramids


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Pyramid of energy A pyramid of energy depicts the energy flow,or productivity, of each trophic level. Due to the Laws of Thermodynamics, each

higher level must be smaller than lower levels,due to loss of some energy as heat (viarespiration) within each level.

producersherbivorescarnivores

Energy flow in :


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Pyramid of numbers A pyramid of numbers indicates the

number of individuals in each trophic level.

Since the size of individuals may varywidely and may not indicate theproductivity of that individual, pyramids of numbers say little or nothing about theamount of energy moving through theecosystem.

# of producers# of herbivores# of carnivores


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Pyramid of standing crop

A pyramid of standing crop indicates how much biomassis present in each trophic level at any one time.

As for pyramids of numbers, a pyramid of standing cropmay not well reflect the flow of energy through thesystem, due to different sizes and growth rates of organisms.

biomass of producersbiomass of herbivoresbiomass of carnivores

(at one point in time)


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Inverted pyramids A pyramid of standing crop (or of numbers) may be

inverted , i.e., a higher trophic level may have alarger standing crop than a lower trophic level.

This can occur if the lower trophic level has a highrate of turnover of small individuals (and high rate of productivity), such that the First and Second Lawsof Thermodynamics are not violated.

biomass of producersbiomass of herbivoresbiomass of carnivores

(at one point in time)


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Pyramid of yearly biomass production

If the biomass produced by a trophic level issummed over a year (or the appropriatecomplete cycle period), then the pyramid of totalbiomass produced must resemble the pyramid of energy flow , since biomass can be equated toenergy.

producersherbivorescarnivores

Yearly biomass production(or energy flow) of:


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Note that pyramids of energy and yearly biomassproduction can never be inverted, since this wouldviolate the laws of thermodynamics.

Pyramids of standing crop and numbers can be inverted ,since the amount of organisms at any one time does notindicate the amount of energy flowing through thesystem.

E.g., consider the amount of food you eat in a year compared to the amount on hand in your pantry .


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The amount of energy available in an ecosystem depends on thetype of vegetation the area can support.

This is measured as an areas net primary productivity (NPP). The higher the NPP, the greater the diversity of animals in thatecosystem.


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Ecosystem Function (cont) #2. Nutrients are recycled

within an ecosystem. Water * Nitrogen Carbon * Phosphorus Oxygen * Sulfur


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Water Cycle

evaporation returns water vapor to the atmosphere condensation of water vapor in the air leads to

precipitation infiltration of rainwater replenishes groundwater supplies

surface runoff of rainwater replenishes surface water supplies


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The Carbon Cycle

Driven by biological forces:photosynthesis and respiration


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Carbon Cycle

Sinks:- Lithosphere limestone (largestreservoir)- hydrosphere ocean (2 nd largest)- Atmosphere in form of CO 2

- biosphere wood, plants, dead animals


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Oxygen Cycle

Essential for animals during respiration,released by plants

Cycles much like the carbon cycle What is threatening this cycle? Forest

deforestation, ocean pollution, etc


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Root noduleson legumes

Cyanobacteria

Driven by biological forces: bacteria

Rhizobium Azotobacter

l


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Nitrogen Cycle 78% of the volume of trophosphere Most complex cycle N2 gas can t be used as is it must be fixed so that

organisms can use it Steps to the cycle: b/c of complexity, no certain order

N Fixation occurs in plant, by bacteria Ammonification Nitrification Assimilation Denitrification

N2 gas is modified by nitrogen -fixing bacteria inlegumes into ammonia (NH 3) NITROGEN FIXATION aids in production of sugars/starches

Bacteria turn wastes and detritus into ammonia AMMONIFICATION released into atm

NH3 is converted into nitrite (NO 2-) which is then usedto produce nitrate (NO 3-) - NITRIFICATION


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Phosphorus Cycle phosphorus is released as rocks erode and

plants assimilate this Very slow process phosphorus passes from one organism to

another in the food chain decomposers release phosphorus during

decomposition Mined for production of fertilizer. Mined in

Tampa, FL


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The Phosphorus Cycle

Driven by physical forces

Sulfur Cycle


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Sulfur Cycle sulfur is released as rocks erode and plants

assimilate this Mostly found under ground like phosphorus H2S is released by decomposers and during

volcanic eruptions; some H 2S in soil isconverted into sulfur by aerobic bacteriaand plants assimilate this

99% of all sulfur in the atm is due to man

SO 2 gas is released by industries; SO 2 thenreacts with water to form H 2SO 4 which fallsto the earth as acid rain


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Water Cycle

condensation of water vapor in the air leads to precipitation evaporation returns water vapor to the

atmosphere infiltration of rainwater replenishes

groundwater supplies surface runoff of rainwater replenishes

surface water supplies


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Ecosystem Concepts and Components

Biomes

Role of climate

Aquaticlife zones


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A. Aquatic biomes cover about 75% of the earth s surface

- Wetlands

- Lakes - Rivers, streams

- Intertidal zones

- Oceanic pelagic biome - Coral reefs

- Benthos


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B. Terrestrial biomes - Tropical forest - Savanna - Desert - Chaparral - Temperate grassland

- Temperate deciduous forest - Coniferous forest - Tundra


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Tropical Forest: Vertical stratification with trees incanopy blocking light to bottom strata. Many treescovered by epiphytes (plants that grow on other plants).


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Temperate Deciduous Forest: Mid-latitudes with moderateamounts of moisture, distinct vertical strata: trees,

understory shrubs, herbaceous sub-stratum. Loss ofleaves in cold, many animals hibernate or migrate then.Original forests lost from North America by logging andclearing.


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Coniferous forest: Largest terrestial biome on earth, oldgrowth forests rapidly disappearing, usually receives lots

of moisture as rain or snow.


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