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APESUnit 3

Ecosystems

Ecology

From the Greek words oikos = “house”

and logos = “study of”

– The study of how organisms interact with one

another and with their environment.

YOU SHOULD KNOW!

The difference between eukaryotic and

prokaryotic cells.

The definition of species.

The types of asexual and sexual

reproduction.

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THE NATURE OF ECOLOGY

Ecology is a study

of connections in

nature.

– How organisms

interact with one

another and with

their nonliving

environment.

Species

Organism

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Population

A group of interacting individuals of the

same species.

Each individual will be different due to

genetic diversity.

Each population lives in a particular

habitat spread over an area called a

range.

Population

Community

The total of all populations living and

interacting in a given area.

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Ecosystem

A community and its nonliving

environment.

Animation: Levels of Organization

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ANIMATION

YOU SHOULD KNOW!

Lower part of atmosphere = troposphere.

Next layer is the stratosphere.

The lowest layers, the hydrosphere and

lithosphere, make up the biosphere.

– Most life exists in the biosphere.

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THE EARTH’S LIFE SUPPORT SYSTEMS

The biosphere

consists of several

physical layers that

contain:

– Air

– Water

– Soil

– Minerals

– Life

Figure 3-6

How is life sustained on Earth?

Three interconnecting factors:

1. The one-way flow of energy from the sun

through the biosphere back into space.

2. Matter cycling

3. Gravity

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Energy Flow

Earth is a closed system.

– Except for the negligible amount of cosmic

matter entering the Earth’s influence and the

miniscule amount of matter that escapes the

planet into space, the Earth is a closed

system.

We already have all of the matter

we will every have.

Energy Flow

Energy, but not matter, is exchanged

between the system and the environment.

Energy Flow

Open Systems

– Both matter and energy are exchanged.

The human body is an open system – matter

(water, food, air) and energy is taken in; waste and

energy is released into the environment.

– Individual organisms depend on both energy

flow and matter flow.

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Animation: Sun to Earth

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ANIMATION

Absorbed

by ozone Visible

Light

Absorbed

by the

earth

Greenhouse

effect

UV radiation

Solar

radiationEnergy in = Energy out

Reflected by

atmosphere (34% ) Radiated by

atmosphere

as heat (66%)

Heat radiated

by the earth

Heat

Troposphere

Lower Stratosphere

(ozone layer)

Components of Ecosystems

Two major parts of EVERY ecosystem

– Abiotic = the non-living parts

– Biotic = the living parts

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Abiotic Factors

Physical Factors for Land Ecosystems

– Sunlight – intensity, duration

– Temperature – variation, extremes

– Precipitation – Frequency, duration, amount

– Wind – Strength, direction, humidity

Abiotic Factors

Physical Factors for Land Ecosystems

– Latitude

– Altitude

– Fire frequency

– Nature of soil – drainage rate, mineral

content, pH

Abiotic Factors

Physical Factors for Water Ecosystems

– Water currents – flow rate, temperature

– Dissolved nutrients

– Suspended solid material

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Abiotic Factors

Chemical Factors for Ecosystems

– Supply of water and air in soil

– Supply of plant nutrients

– Toxic substances dissolved in soil or water

– Salinity (aquatic ecosystems)

– Level of dissolved oxygen (aquatic

ecosystems)

Animation: Roles of Organisms

in an Ecosystem

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ANIMATION

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Animation: Diet of a Red Fox

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ANIMATION

Abiotic and Biotic Factors

Range of Tolerance

Each population has a range of chemical

and physical conditions that must be

maintained for populations of a particular

species to stay alive and grow, develop,

and function normally.

– Individuals of a population will differ due to

small differences in genetic make-up, age,

and health.

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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 the

species.

– These may change during an individuals

lifetime.

Range and Habitat

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Law of Tolerance

Threshold Affect

The harmful or fatal effect of a small

change in environmental conditions that

exceeds the limit of tolerance of an

organism or population of a species.

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Threshold Affect

– Example: Swimmers

ear is caused by a

fungus. Changing the

pH in the ear canal

even a little bit can

prevent or increase

the infection.

Limiting Factors

Single factor that limits the growth,

abundance, or distribution of the

population of a species in an ecosystem.

– Example 1: The salinity of the soil in an

estuary may limit plant growth as you get

closer to the ocean.

Limiting Factors

Example 2: A deserts

limiting factor is the

amount of

precipitation.

Organisms must

adapt to preserve

water or perish.

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Limiting Factors

Example 3: Floods

limit food, shelter, and

may bring toxic

materials into an

environment.

Limiting Factors

Example 4: Lack of

shelter can limit the

number of

organisms/size of the

population.

Limiting Factor Principle

Too much or too little of any abiotic factor

can limit or prevent growth of a population

of a species in an ecosystem, even if all

other factors are at or near the optimum

range of tolerance for the species.

– Examples

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Limiting Factor Principle

Important limiting factors are:

– DO (dissolved oxygen)

– Temperature

– Sunlight

– Nutrient availability

– Salinity

YOU SHOULD KNOW!

Autotrophic organisms

Heterotrophic organisms

The role and process of photosynthesis

Definition of herbivore, carnivore, and

omnivore

The difference between aerobic and

anaerobic respiration

Biotic Factors

Three primary types of biotic factors:

1. Producers

2. Consumers

3. Decomposers

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Producers

Autotrophs (Plants)

Most convert sunlight energy to chemical

energy in the form of glucose.

– Photosynthesis

Some do this by chemosynthesisConverting simple compounds from the

environment into more complex nutrients.

– Very special bacteria

Sun

Chloroplast

in leaf cell

Light-dependent

Reaction

Light-independent

reaction

Chlorophyll

Energy storageand release(ATP/ADP)

Glucose

H2O

Sunlight

O2

CO2

6CO2 + 6 H2O C6H12O6 + 6

O2

Animation: Linked Processes

PLAY

ANIMATION

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Producers

Consumers

Organism that cannot synthesize the organic

nutrients it needs and gets its organic nutrients

by feeding on the tissues of producers or of

other consumers; generally divided into primary

consumers (herbivores), secondary consumers

(carnivores), tertiary (higher-level) consumers,

omnivores, and detritivores (decomposers and

detritus feeders).

Primary Consumers

Organism that feeds on all or part of plants

(herbivore) or on other producers.

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Secondary Consumer

Organism that feeds only on primary

consumers.

Tertiary Consumers

Also called higher-level consumers.

Animals that feed on carnivores. They

feed at high trophic levels in food chains

and webs.

– Examples are hawks, lions, bass, and sharks.

Do you agree?

Detritivores

Consumer organism that feeds on detritus,

parts of dead organisms, and cast-off

fragments and wastes of living organisms.

The two principal types are detritus

feeders and decomposers.

– Detritus feeders do not break down their

nutrients to a simple organic compound.

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Decomposers

Organism that digests parts of dead organisms and cast-off fragments and wastes of living organisms by breaking down the complex organic molecules in those materials into simpler inorganic compounds and then absorbing the soluble nutrients. Producers return most of these chemicals to the soil and water for reuse. Decomposers consist of various bacteria and fungi.

Decomposers

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Animation: Matter Recycling

and Energy Flow

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ANIMATION

Animation: Energy Flow

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ANIMATION

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Animation: Prairie Trophic

Levels

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ANIMATION

Fo

od

We

b

Animation: Categories of Food

Webs

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ANIMATION

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Animation: Rainforest Food

Web

PLAY

ANIMATION

Animation: Prairie Food Web

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ANIMATION

Energy Flow in an Ecosystem: Losing

Energy in Food Chains and Webs

Ecological

efficiency:

percentage of

useable energy

transferred as

biomass from

one trophic level

to the next.

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Animation: Energy Flow in Silver

Springs

PLAY

ANIMATION

Productivity of Producers:

The Rate Is CrucialGross primary

production

(GPP)

– Rate at which an

ecosystem’s

producers

convert solar

energy into

chemical energy

as biomass.

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Gross primary productivity

(grams of carbon per square meter)

What are nature’s three most

productive and three least

productive systems?

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Average net primary productivity (kcal/m2 /yr)

Open ocean

Continental shelf

Lakes and streams

Estuaries

Aquatic Ecosystems

Extreme desert

Desert scrub

Tundra (arctic and alpine)Temperate grassland

Woodland and shrubland

Agricultural land

Savanna

North. coniferous forest

Temperate forest

Terrestrial Ecosystems

Tropical rain forest

Swamps and marshes

SOIL: A RENEWABLE

RESOURCESoil is a slowly renewed resource that

provides most of the nutrients needed for

plant growth and also helps purify water.

– Soil formation begins when bedrock is broken

down by physical, chemical and biological

processes called weathering.

Mature soils, or soils that have developed

over a long time are arranged in a series of

horizontal layers called soil horizons.

SOIL: A RENEWABLE RESOURCE

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Layers in Mature Soils

Infiltration: the downward movement of

water through soil.

Leaching: dissolving of minerals and

organic matter in upper layers carrying

them to lower layers.

The soil type determines the degree of

infiltration and leaching.

Soil Profiles of the

Principal

Terrestrial Soil

Types

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Animation: Soil Profile

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ANIMATION

MATTER CYCLING IN

ECOSYSTEMS

Nutrient Cycles: Global Recycling

– Global Cycles recycle nutrients through the

earth’s air, land, water, and living organisms.

– Nutrients are the elements and compounds that

organisms need to live, grow, and reproduce.

– Biogeochemical cycles move these substances

through air, water, soil, rock and living

organisms.

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The Water Cycle

Animation: Hydrologic Cycle

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ANIMATION

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Water’ Unique PropertiesThere are strong forces of attraction between

molecules of water.

Water exists as a liquid over a wide

temperature range.

Liquid water changes temperature slowly.

It takes a large amount of energy for water to

evaporate.

Liquid water can dissolve a variety of

compounds.

Water expands when it freezes.

Effects of Human Activities

on Water Cycle

We alter the water cycle by:

– Withdrawing large amounts of freshwater.

– Clearing vegetation and eroding soils.

– Polluting surface and underground water.

– Contributing to climate change.

The Carbon Cycle:

Part of Nature’s Thermostat

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Animation: Carbon Cycle

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ANIMATION

Effects of Human Activities

on Carbon Cycle

We alter the carbon cycle by adding excess CO2

to the atmosphere through:

– Burning fossil fuels.

– Clearing vegetation faster than it is replaced.

The Nitrogen Cycle:

Bacteria in Action

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Animation: Nitrogen Cycle

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ANIMATION

Effects of Human Activities

on the Nitrogen Cycle

We alter the nitrogen cycle by:

– Adding gases that contribute to acid rain.

– Adding nitrous oxide to the atmosphere through

farming practices which can warm the

atmosphere and deplete ozone.

– Contaminating ground water from nitrate ions in

inorganic fertilizers.

– Releasing nitrogen into the troposphere through

deforestation.

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Effects of Human Activities

on the Nitrogen Cycle

Human activities

such as

production of

fertilizers now fix

more nitrogen

than all natural

sources

combined.

Figure 3-30

The Phosphorous Cycle

Animation: Phosphorous Cycle

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ANIMATION

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Effects of Human Activities

on the Phosphorous Cycle

We remove large amounts of phosphate from

the earth to make fertilizer.

We reduce phosphorous in tropical soils by

clearing forests.

We add excess phosphates to aquatic

systems from runoff of animal wastes and

fertilizers.

The Sulfur Cycle

Animation: Sulfur Cycle

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ANIMATION

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Effects of Human Activities

on the Sulfur Cycle

We add sulfur dioxide to the atmosphere by:

– Burning coal and oil

– Refining sulfur containing petroleum.

– Convert sulfur-containing metallic ores into free

metals such as copper, lead, and zinc releasing

sulfur dioxide into the environment.

The Gaia Hypothesis:

Is the Earth Alive?

Some have proposed that the earth’s various

forms of life control or at least influence its

chemical cycles and other earth-sustaining

processes.

– The strong Gaia hypothesis: life controls the

earth’s life-sustaining processes.

– The weak Gaia hypothesis: life influences the

earth’s life-sustaining processes.

Biodiversity Loss and Species

Extinction: Remember HIPPOH for habitat destruction and

degradation

I for invasive species

P for pollution

P for human population growth

O for overexploitation