ecology 2 hndout_1

7/31/2019 Ecology 2 Hndout_1

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Ecology 2

Ecology energetics

Energy flow through ecosystems

Nutrient cycling

The carbon cycleThe nitrogen cycle

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Learning outcomes

Construct a diagram of a generalisedcarbon cycle

Construct a diagram of a generalisednitrogen cycle

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Trophic level

A theoretical term which relates to the transfer ofmatter or energy through a community from one levelto the next

This can take place by means of: Grazing a herbivore will consume plant material, the

primary producers, and in so doing will transfer the energyfrom the plant to the animal

Predation an organism may prey on the herbivore suchas a carnivore. Again energy is transferred from oneanimal to another

The chain of transferring energy by one animal eatinganother can occur several times but it will eventuallyend. It ends with a dead animal that is decomposed bybacteria and fungi

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Trophic level

To determine the trophic level of anorganism, note the number of steps since

their fixation in photosynthesis.

Organisms on the same trophic levelwould go through the same number of

steps since their fixation in photosynthesis

A consumer will be one trophic level aboveits resource4


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Trophic level

All the organisms within an ecosystem at thesame number of steps away from the energyinput into the system can be described asbeing at the same trophic level. Trophic levels

can be labelled in the following way:Primary producersPrimary (first tropic level), secondary (second

tropic level), tertiary (third tropic level), quaternary

(fourth tropic level) consumersDecomposers

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Trophic level

Identify the trophiclevel for the followingorganisms:

fish blue whale krill birds

Which organismswould you place onthe same trophiclevel?


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Energy flow through an

ecosystem

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Characteristics of an ecosystem

Energy flows throughfood webs

Cycling of theproduction anddegradation organic

matter

Transformation andcycling of nutrientelement

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Energy flow through an

ecosystem Energy flows in one

direction only Transferred between

trophic levels

It is an inefficient process Minerals are recycled

Autotrophs accumulateminerals

Nutrients pass throughfood chains

Nutrients are recycled backinto the abiotic part of theecosystem by thedecomposers

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Food pyramids

Following the 10% energyrule (only 10 % of theavailable energy istransferred to the next levelthe bulk of the rest is lost asheat) it would take 10,000 kgof phytoplankton to make1kg of Orca in this marinefood chain

Baleen whales feed directlyon zooplankton how much

phytoplankton would it taketo make 1kg of baleenwhale?


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Pyramids of biomass and

number

Pyramid of biomass Pyramid of number

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Nutrient cycling aquatic

1.The cycle begins whenorganisms die and sink to thebottom. Here they aredecomposed by a variety oforganisms on the sea bed

2.The nutrients are releasedinto the water as a result ofturbulence currents andtides, and made available tothe phytoplankton, which arethe producers

3.The other organisms feed offthe phytoplankton and whenthey die their nutrients arerecycled.

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Nitrogen cycle

Nitrogen fixing

bacteria in the soiland root nodules of

leguminous plantse.g. clover peas

beans

Plant and

animal proteins


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Nitrogen cycle

Life on earth requiresnitrogen for protein andnucleic acids. Air, whichis 79% nitrogen gas(N2), is the major

reservoir of nitrogen. But most organisms

cannot use nitrogen inthis form.

Plants must securetheir nitrogen in "fixed"form

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Nitrogen cycle

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The human impact

Climate changeFactors contributing toward climate change,

carbon emissions (the two greenhouse gassesCO2 and methane), deforestation

Algal blooms in lakes and rivers Imbalance in the nitrogen cycle

Impacting on ecosystemsFarming (intensity, GM), pollutants, species

endangerment, introduction of species to differenthabitats (biological control)

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What is the carbon footprint of

the food we eat?

Which one of these foods has the highestcarbon foot print?

a) Homegrown cherry tomatoes out of seasonb) Bananas produced in the Caribbeanc) Asparagus grown in Chile

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Carbon cycle

Carbon is found in one of three forms:organic carbon i.e. as part of a biomoleculeinorganic carbon as carbonates e.g. in

limestonecarbon dioxide gas the product of

respiration or combustion.

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Cycling of CO2

PLANTS

CO2 gas

respiration

combustion

photosynthesis

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DECOMPOSERS

ANIMALS

feeding

PLANTS

CO2 gas

respirationphotosynthesis

feeding

Cycling of CO2

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FOSSILS

DECOMPOSERS

PLANTSANIMALS

CO2 gas

respirationphotosynthesiscombustion

Cycling of CO2

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carbonates

HYDROGENCARBONATES in

solution

CO2 gas

Out

gassing

dissolving

FOSSILS

ANIMALS

respirationphotosynthesis

feedingcombustion

feedingDECOMPOSERS

PLANTS

2007 Paul Billiet ODWS

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The carbon cycle

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Questions

1. Which of the following is not considered apopulation?

a) the ginkgo trees in New York Cityb) the birds in your localityc) the human inhabitants of Bristold) the grizzly bears of Alaska

2. Throughout most of North America, large carnivoreshave either been driven to local extinction or theirpopulations are at extremely low levels. Explain howthe loss of carnivore populations may have changedthe vegetation of North America.

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Question

Nitrogen is a limiting nutrient to plantgrowth in most ecosystems. To increase

plant production, fertilizers that contain

nitrogen (and phosphorous) are used.What effects might this influx of nitrogen

have on ecosystems?

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Question

What constitutes the greatest threat to thefuture of the planet, the rapidly growing

population in developing parts of the world

or high resource consumption in thedeveloped world?

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ecology 2 hndout_1

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