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Principles of EcologyCh. 13

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13.1 Ecologists study relationships

Ecology: the study of the interactions among living things, and between living things and their surroundings.

Eco = environmentology = study of

This is studied at different levels

OrganismOrganism

1. organism - an individual living thing, such as an alligator.

LEVELS OF ORGANIZATION

OrganismOrganism

Population

Population

2. population is a group of the same species that lives in one area.

- Several alligators living together.

LEVELS OF ORGANIZATION

OrganismOrganism

Population

Population

Community

Community

3. A community is a group of different species that live together in one area.

- Alligators, birds, fish, plants

all living together in a swamp.

LEVELS OF ORGANIZATION

OrganismOrganism

Population

Population

Community

CommunityEcosystem

Ecosystem

4. An ecosystem includes all of the organisms as well as the non-living things such as; climate, soil, water, rocks and other in a given area.

LEVELS OF ORGANIZATION

Organism

Organism

PopulationPopulation

Community

CommunityEcosystem

Ecosystem

Biome

5. A biome is a major regional or global community of organisms characterized by the climate conditions and plant communities that thrive there.

LEVELS OF ORGANIZATION

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Ecological research methods include observation, experimentation, and modeling.

Observation

•Direct surveys used for easy to spot and follow species employ binoculars or scopes.

•Indirect surveys are used for species that are difficult to track and include looking for other signs of their presence.

•Feces or a recent kill.

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1._____________________________________

2. _____________________________________

3._____________________________________

Quadrat Sampling

TAGGING / RADIO TELEMETRY

Mark and Recapture –

•Capture a number organisms- mark/tag them

•Recapture a portion

•The number of marked organisms if proportional to the size of the whole population.

What is the population of turtles in the rectangle: _______

MEASURE THE SIZE OF THE SQUARE: _______________

TIME YOURSELF AND COUNT THE NUMBER OF TURTLES: ____

DETERMINE HOW MANY SQUARES CAN FIT INTO THE LARGER RECTANGLE ON THE PREVIOUS PAGE: _________

CALCULATE THE POPULATION OF TURTLES IN THE RECTANGLE: ___________________________________

Where your two numbers relatively close? _____________________

What is the advantage of quadrat sampling? _____________________

What is the disadvantage of quadrat sampling? _____________________

What type of organism do you think would be best suited for quadrat sampling? ____________________________________________________

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Experiments: Performed in the lab or in the field.

• Lab experiments:

• Positive = More control

• Negative = Doesn’t always reflect what happens in nature

•Field experiments:

• Positive = More accurate picture of what happens in nature

• Negative = May not help determine cause and effect

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Modeling:

•Computer and Mathematical models

• “What would happen if…”

• Predict outcomes

• Allows scientists to learn about organisms or ecosystems in ways that would not be possible in a natural or lab setting.

1.What are the five different levels of organization studied by ecologists?

2. Describe the three general methods used by ecologists to study organisms.

3. What ecological research methods would you use to study bird migration? Explain your choices.

4.How might an ecologist use modeling to study fire in a forest ecosystem? What might be some key variable used to create the model?

ALL LIVING THINGS

BACTERIA-PROTIST-FUNGUS-PLANTS-ANIMALS

ALL NON-LIVING THINGS

WATER-SUN-SNOW-CLOUDS-ROCKS-MOUNTAINS

13.2 Biotic and Abiotic Factors

Changing one factor can affect many other factorsBiodiversity

•Biodiversity is the assortment, or variety, of living things in an ecosystem.

•Rainforests have more biodiversity than other locations in the world, but are threatened by human activities.

Keystone species is a species that has an unusually large effect on its ecosystem.Example = Beaver

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keystone

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creation ofwetlandecosystem

increased waterfowlPopulation

increased fishpopulation

nesting sites for birds

keystone species

1.Select an ecosystem that is familiar to you and describe the biotic and abiotic factors that exist there.

2. How would the removal of a keystone species affect an ecosystem’s biodiversity?

3. Name an abiotic factor. Explain how a change in an abiotic factor would affect biodiversity.

4.Humans are sometimes described as being a keystone species. Does this label fit? Why or why not?

13.3 Energy in Ecosystems`Producers provide energy for other organisms in

an ecosystem.

•Producers- make their own food – also called autotrophs

•Consumers – get energy by eating – also called heterotrophs

Almost all producers obtain energy from sunlight.

•Photosynthesis in most producers uses sunlight as an energy source.

Chemosynthesis in prokaryote (bacteria) producers uses chemicals as an energy source.

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1.How does the stability of an ecosystem depend on its producers?

2. What are the two processes used by producers to obtain energy?

3. Few producers live deep below a lake’s surface. Suggest an explanation for this pattern.

4.Could producers survive without consumers? Explain why or why not?

5. Could consumers survive without producers? Why or why not?

13.4 Food Chains and Food WebFood chains and food webs model the flow of

energy in an ecosystem.

• Show feeding relationships for one chain of producers and consumers in an ecosystem

• Arrow always points in the direction the energy is going.

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DESERT COTTONTAILGRAMA GRASS HARRIS’S HAWK

Consumers are not all alike.

•Herbivores eat only plants.

•Carnivores eat only animals.

•Omnivores eat both plants and animals.

•Detritivores eat dead organic matter.

•Decomposers are detritivores that break down organic matter into simpler compounds.

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•Specialists are consumers that primarily eat one specific organism or a very small number of organisms.

•Ex: Florida Snail Kite – eats only snails

• Generalists are consumers that have a varied diet.

Ex: Grey wolf24

Trophic Levels- Feeding levels in a food chain

•Primary consumers are herbivores that eat producers.

•Secondary consumers are carnivores that eat herbivores.

•Tertiary consumers are carnivores that eat secondary consumers.

•Omnivores, such as humans that eat both plants and animals, may be listed at different trophic levels in different food chains.

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Food Web•Shows many

interconnected food chains in an ecosystem

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Identify three food chains from this food web.

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1.Name the producers in the salt marsh community. ___________________________

2.Name four primary consumers in the salt marsh community. __________________ ___________________ ___________________ _____________________

3.Name four secondary consumers in the salt marsh community. _________________ ___________________ ___________________ _____________________

4.Name an animal in the salt marsh community that eats both plants and animals. _________________________________________________________________

5.Name the two animals at the top of the salt marsh food web. _________________________________________________________________

6.Why are the decomposers shown as the are in this picture? __________________________________________________________________

7.Who is the “highest’ consumer? ________________________________

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1.Why are food chains especially useful for describing the relationships of specialists?

2. What happens to energy as it flows through a food web?

3.Only a small percentage of all consumers are specialists. What danger does a specialist face that a generalist does not?

4.How might the stability of an ecosystem be affected if all the decomposers were suddenly removed?

Water cycles through the environment. •The hydrologic, or water cycle is the circular

pathway of water on Earth.

•Organisms all have bodies made mostly of water.

precipitation condensation

transpiration

evaporation

water storagein ocean

surfacerunoff

lake

groundwater

seepage

Elements essential for life also cycle through ecosystems.

•A biogeochemical cycle is the movement of a chemical through the biological and geological parts of an ecosystem.

•The Oxygen cycle involves photosynthesis and respiration.

•Oxygen cycles indirectly through an ecosystem by the cycling of other nutrients.

fossil fuels

photosynthesis

carbon dioxidedissolved in water

decompositionof organisms

respiration

carbondioxidein air

photosynthesis

combustionrespiration

Carbon is the building block of life.

• The carbon cycle moves carbon from the atmosphere, through the food web, and returns to the atmosphere.

• Carbon is emitted by the burning of fossil fuels.

• Some carbon is stored for long periods of time in areas called carbon sinks.

nitrogen inatmosphere

animals

denitrifyingbacteria

nitrifyingbacteria

nitrifyingbacteria

ammonium

ammonification

decomposers

plant

nitrogen-fixingbacteria in soil

nitrogen-fixingbacteria in

roots

nitrates

nitrites

The nitrogen cycle mostly takes place underground.

• Some bacteria convert gaseous nitrogen into ammonia through a process called nitrogen fixation.

• nitrogen-fixing bacteria live in roots of plants; others live freely in the soil.

• bacteria change the ammonium into nitrate.

• moves through the food web and returnsto the soil duringdecomposition.

geologic upliftingrain

weathering ofphosphate from rocks

runoff

sedimentationforms new rocks

leaching

phosphate in solutionanimals

plants

decomposers

phosphatein soil

The phosphorus cycle takes place at and below ground level.

• released by the weathering of rocks.

• moves through the food web and returns to the soil during decomposition.

• leaches into groundwater from the soil and is locked in sediments.

• added to environment by both mining and agriculture

•How does the hydrologic cycle move water through the environment?

•What are the four elements that cycle through ecosystems and why are they important?

•Why might farmers plants legumes such as peas to improve the nitrogen levels in their soil?

•Explain the importance of decomposers to the overall biogeochemical cycle

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energy transferredenergy

lost

An energy pyramid shows the distribution of energy among trophic levels. • Energy pyramids compare energy used by producers and other organisms on trophic levels.

• Up to 90 percent of the energy = lost as heat between each level

• Only 10 percent of the energy at each tier is transferred from one trophic level to the next.

Pyramids for Biomass and numbers

•Biomass is a measure of the total dry mass of organisms in a given area.

tertiaryconsumers

secondaryconsumers

primaryconsumers

producers

75 g/m2

150g/m2

675g/m2

2000g/m2producers 2000g/m2

A pyramid of numbers shows the numbers of individual organisms at each trophic level in an ecosystem.

tertiaryconsumers

secondaryconsumers

primaryconsumers

producers

5

5000

500,000

5,000,0005,000,000producers

• A vast number of producers are required to support even a few top level consumers.

1.How does an energy pyramid help to describe energy flow in a food web?

2. What is the difference between a biomass pyramid and a pyramid of numbers?

3. How would you draw a pyramid of numbers for a dog with fleas? What shape would the pyramid take?

4.If each level in a food chain typically loses 90% of the energy it takes in, and the producer level uses 1000 kilocalories of energy, how much of that energy is left after the third trophic level?