Environmental Science Unit # 3 Ecosystem Dynamics

Environmental Science Unit # 3 Ecosystem dynamics

I. What are ecosystems?

Ecosystem – all of the living organisms in a region as well as the nonliving resources in a region

Ecology – the science of studying organisms and their interaction with other organisms and the abiotic world around them.

A. Two major components of ecosystem Biotic + Abiotic

Biotic community – all of the living components of a region

- Biodiversity of the area

Described species =1.4 million

Estimates to 100 million

Domains

Archaea – ancient bacteria

Eubacteria – true bacteria

Eukarya – all other gourps

3.5 BYA first bacteria

Evolved 1.5 million years without other organisms

10 X the biomass of all eukaryotes

Important as saprophytes and pathogens

Kingdom

Animals 1.3 Million sp.

Insects – 751,000 sp.

Mollusks – 112,000 sp.

Fish – 29,000 sp.

Amphibians – 6,000 sp.

Reptiles – 8,000 sp

Mammals – 5,500 sp

Plants – 248,400 sp

Fungi – 69,000 sp

Protists – 57,700 sp

Abiotic component – nonliving resources in the area

- Air

- Water

- Soil

- Rock

- Climate

- wind

Earth

Biosphere – anywhere on Earth which life can be found

Lithosphere – Upper mantle, rock and soil – 29.2%

Hydrosphere – All regions of Earth with water -70.8%

Ice-

Polar ice

Glaciers

Icebergs

Permafrost

Water vapor-

Freshwater – 2.12%

Underground

- percolating

- aquifers

Saltwater – 68.68%

Oceans

Inland brackish waters

Atmosphere – Gasses surrounding Earth to 48 km 30 miles

Troposphere – closest to Earth to 17 km 11 miles

Stratosphere – 17-48 km

B. Interactions within an ecosystem

Biotic to biotic

Predator / Prey

Symbiosis

Mutualism – both benefit

Commensalism – one helped other unaffected

Parasitism –

Interspecies interactions – between species

Pollination

Seed dispersal

Parasite reduction

Biological services

Intraspecific interactions - within a species

Altruism

Fighting

Schooling

Biotic to Abiotic

Nutrient cycling

Weathering

Nest / Den building

Habitat modification - Keystone species – beavers, elephants, bison

Abiotic to biotic

Fire

Weathering

II. How does an ecosystem function?

Ecosystems must have influx of energy and matter.

Energy – Constant influx of solar energy or other high energy source

1st law of thermodynamics

Finite

Maximize efficiency but cannot increase overall energy reserve

2nd law of thermodynamics

Reduction of energy quality during use

ENTROPY

What happens to energy on Earth?

- Some reflected off atmosphere ~ 34%

- Heat Earth and returned to space as heat leaving atmosphere ~ 66 %

- Little enters food chain via primary productivity ~0.23 %

High Quality Solar Energy  Chemical Potential Energy  Heat

Natural greenhouse effect – atmospheric gasses CO2, CH4, H2O, NO2, O3

- blanket Earth trapping radiant heat

- allow Earth to be warm enough for life

What happens to matter on Earth?

Matter – Constant cycling of matter through living organisms and back to

abiotic environment

- Law of conservation of mass

- Gravity – holds materials

- particular interest in CHNOPS

Matter linked using energy – Anabolic + Catabolic processes

Photosynthesis

Aerobic respiration

Anaerobic Respiration

Incorporated into living material

Flesh

Bone

Stem

Trunk

Used as intermediate molecules

Food

Nutrients

Air

Sequestered – moved to rock strata

Fossil fuels

Carbonate rocks – CaCO3

Marine Sediments

Recycled Biogeochemical cycles – decomposition, combustion,

Carbon / Oxygen

Nitrogen

Phosphorous

Water

Sulfur

III Abiotic components of an ecosystem and ecosystem dynamics

The abiotic components of an ecosystem determine the biotic community

A. Climate – temperature and precipitation

- delineates all terrestrial ecosystems

- determines flora and fauna types

- leads to distinct BIOMES

Biome – region of the Earth containing characteristic biotic community

- Deciduous hardwood forest –

- Taiga – northern coniferous forest

- Desert -

-Tundra –

Often due to latitude

Often due to geography

B. Aquatic life zones – regions of the hydrosphere with different characteristic

life forms

- Factors which change biotic community

- Salinity

- Dissolved oxygen

- Current

- Solar influx

- Turbidity

- Nutrients

- Substrate

- pH

C. Law of tolerance – Biotic members of a community are determined and

limited by abiotic factors in an environment.

- Organisms have a range of tolerance

- Some organisms are well adapted to broad ranges of tolerance

- Some very narrow

- There is generally a optimum level for a particular organism

- As you move away from this optimum level

Physiological stress increases

- This stress limits population growth

D. Limiting Factors – an abiotic factor which limits population size

- Again a range

- Too little

- Too high

- Density dependant – limiting factor which is changed by number of

Organisms – nutrients, nesting sites, water

- Density independent – numbers do not effect - fire, drought

E. Biodiversity – The number of different life forms in a given area

- ultimately controlled by abiotic factors

- High sunlight, temperature, precipitation = High primary productivity

- High primary productivity = large amount of available energy (food)

- High levels of energy = high biodiversity

TropicalRain Forest – 200-400 cm / Yr precipitation – warm climate

- A typical four square mile patch of rainforest contains as many as 1,500 flowering

plants, 750 species of trees, 400 species of birds and 150 species of butterflies.

NATURE CONSERVANCY

- Up to 300 tree species per hectare 10,000 M2 2.5 acres

- ½ Earth’s terrestrial species

Tundra –15-25 cm /Yr precipitation – very cold

- 1,700 species of flora and only 48 land mammals can be found

IV. Ecosystems – the players

- Autotrophs

- photoautotrophs

- chemoautotrophs

- Heterotrophs / consumers

- Decomposers / Detritivores / Saprophytes

Detritivores – animals which eat detritus

Saprophytes – bacteria and fungi

- Herbivores

- Omnivores

- Carnivores

IIV Ecosystems and energy flow energy pyramids

How do we get our energy

All energy moving through an ecosystem originates from the abiotic world

Energy is trapped by autotrophs

- Biomass – mass of living material

- Base of all food chains

Heterotrophs depend upon autotrophs to supply them with food

3. Almost all energy for any ecosystem originates from the sun

Gross Primary productivity- the total amount of light energy harnessed by autotrophs in an environment

- Some of this energy must be used by the autotroph itself

Growth, reproduction, metabolism

- leads to NPP – Net Primary Productivity

Net Primary Productivity = amount of energy available for use by

heterotrophs in the environment

this is very low percentage of total energy entering ecosystem (0.023%)0.023% of suns energy hitting earth converted to chemical potential E.
Measured in kcal/ m2/yr or g/m2/yr

- Rainforest - ~ 9000 kcals

- Tundra ~ 600 kcals

- Deciduous HW forest ~ 5800

the amount of primary productivity greatly effects the number of organisms in the ecosystem

high primary productivity = high biodiversity, more energy
low primary productivity = low biodiversity, low energy

C. The energy pathway

1. energy pyramids- a visual simulation of how energy moves through an

ecosystem

a. trophic level- level of energy transfer in an ecosystem or level of

energy

pyramid

b.1st trophic level- autotrophs or producers

-always autotrophs

-build base of pyramid

-support all life

c. 2nd trophic level – first order consumer

-first order consumer- organism which feeds directly on autotroph

-herbivore- organism which eats only plants

-omnivore- organism which eats plants and animals

d. 3rd trophic level- second order consumer

- second order consumer- organism which feeds on 1st order

consumer

ex. grass= producer --> mouse= first order consumer --> snake= second order consumer

- carnivore- meat eater

- omnivore- plant and animal eater eat both producers and

consumers

- saprophytes- organisms which feed on dead material (decomposers)

2. Food chain

-a linear movement of materials through the environment

-Ex. grass - autotroph/producer

mouse- 1st order consumer- herbivore

snake- 2nd order consumer- carnivore or omnivore

hawk- 3rd order consumer – carnivore

3. Food web

-all possible relationships between organisms

-group of food chains

-includes decomposers ( bacteria and fungi ) breaking down materials and returning to environment

4. Energy amounts in relationship to trophic level

Ecological efficiency – amount of energy transferred from one

trophic level to next

- Range 2-40 %

- Typical 10%

- Rule of 10% - 10% of energy passes on to next level

- ENTROPY

energy can neither be created or destroyed law of conservation of energy
However it can be lost

1) lost as heat

2)lost as work (organism moving ect.)

3)lost because all organisms are not eaten by next trophic level

-because energy is lost there always must be higher numbers of organisms in a lower tropic level than in higher trophic levels

-example

trophic level one has 10,000 calories

calorie = the amount of heat energy needed to raise 1 gram of water from 14.5 to 15.5 degrees C. at one atmosphere pressure

trophic level two has 1000 calories as 90% of energy was lost

Trophic level three has 100 calories and so on

IIIV. Soils and Ecosystems

A- What is soil?

Soil – mixture of abiotic and biotic components covering most of the

Pedosphere – between atmosphere and lithosphere – Pedology

Earth’s land.

Abiotic – Bedrock

Regolith – broken down bedrock component

Eroded materials

Clay – chemical weathering

Silt - Physical weathering

Sand

Gravel

Minerals

Leached out

Modified in situ

Biotic – living and once living component

Leaf litter

Humus – partially decomposed organic material

Flora and fauna

Bacteria

Fungi

Worms

Nematodes – unsegmented round worm

Annelids

Insects

Small higher organisms

Mammals

Birds

Reptiles

B - Why is soil important?

1) Soil acts as substrate for terrestrial plants

2) Soil acts to provide nutrients to plants

Nitrogen

Phosphorous

Potassium

Other nutrients

Calcium

Sulfur

Magnesium

Trace minerals an elements

3) Habitat for many organisms

4) Sight of plant germination

5) Natural services

Cleansing water – removes toxins from water

Water storage – stop flooding

Sight for decomposition

Carbon sequestration

C - Soil formation

- Slow

- 1 cm 15 -100 yrs

- From decaying material

- From weathering of rock

Localized

Sedimentation

- From interaction with the biotic environment

Bacteria, Fungi, Plants, and animals

- Adding materials

- Modifying through decomposition materials

- Through physically disturbing soil

D - What factors affect soil formation?

Climate – Temperature and precipitation

- Temperature

Increase helps promote decomposition

Decrease slows decomposition

Freeze thaw cycles

Weathering

Movement of soil components – frost heaving

- Precipitation

Low – slows decomposition

High – increases decomposition

Increases leaching

Increases chemical alterations

Increases weathering

Increase or decrease sedimentation

Biotic – living components

- Add to humus

- Increase mixing of materials

- Increase weathering

- Decrease erosion

Parent material – rock soil is forming from / on

- Chemistry of soil often controlled by bedrock

- Limestone – raise pH calcium carbonate

Topography – slope

- changes water patterns

- changes sedimentation patterns

E - Soil Horizons

- Soil forms in layers O A B C

O Horizon – Leaf litter

- Very top layer of soil

- Undecomposed and partially decomposed organic material

- plant material

- wastes

- Nutrient rich

- Habitat for many organisms

A Horizon – topsoil

- Partially decomposed organic material

- Humus

- Little inorganic material

- Zone of leaching

B Horizon – Subsoil – illuvial horizon

- Mostly mineral soil

- Little humus

- Site which receives leachate

- Often site of in situ synthesis of materials

- Site of clay buildup

C Horizon – regolith

- Partially decomposed parent rock

- Some chemical weathering and modification of parent materials

F- Soils and biomes

- soils form in specific manners depending upon biome

Desert Biome – High heat – Low precipitation – Low Biomass

0-25 cm Yr

Grassland Biome – Temp varies – Low precipitation – Low biomass

Drought US Prairies – 50-75 cm

TropicalRain forest – High Temp – High Precipitation – High Biomass

Deciduous hardwood forest – Varied temps – High Precipitation – High Biomass

- Heavy forest litter each year

- Sufficient water for decomposition and leaching of materials

- Cold enough to slow decomposition

- Rich A horizon with Humus

- Biotic mixing is high

- B horizon

Northern coniferous forest – Cold temps - Low precipitation – High Biomass

G – Man and soils

Erosion –

Farming

Deforestation

Construction

Practices

Increased runoff

Grazing

Problems Associated

Flooding

Turbidity

Loss of soil

Salinization – buildup of salt in soils

Irrigation

Problems associated

Loss of arable land

Compaction - Creates impermeable layers (hardpan ) in soil

Construction

Heavy traffic

Problems

Increases runoff

Erosion

Aquifer not recharged

Desertification – loss of soil water

Mining

Overgrazing

Deforestation

Irrigation

Problems

Loss of cover plants

Increase erosion

Loss of arable land

Increased runoff

III. Biogeochemical cycles

water cycle

1. water is needed by all life

medium or place to live
for chemical reactions (photosynthesis)
reproduction (liquid for sperm)
as limiting factor for plants Often delineates BIOMES
component of life about 60% of all living things

Water cycle

evaporation- liquid water turning to water vapor

1) increased with temp.

2) increased with air movement

3) 84% of atmospheric water from ocean

4) Natural service – purifies water

transpiration- the evaporation of water through the leaves of plants

1)wicking of water from ground ( Evaporation cohesion theory )

2)leaves have stomata and waxy coating to stop

c. Sublimation – ice to vapor

d. condensation- water vapor to liquid

1) due to cooling

2) in clouds

e. precipitation- falling of water as rain snow sleet hail

f. run off – liquid water flowing to body of water lake pond ocean

1)evaporation occurs here

2)or absorption into ground

g. Infiltration / perculation into ground or plants

1) round- to aquifer or water table- will run out as spring or

drawn out by plants humans

.2) plants- used for life processes or transpired

Man and the water cycle

removing water from FW and aquifers

1)reduces amount of available fw

2)can cause saltwater intrusion

3)can cause land subsidence- land sinking

land clearing and development

1)Increases impervious surfaces

2)increases runoff

3)decreases absorption

4)aquifers tend to lower

5)increases erosion

Pollution

1)addition of toxins

2)addition of nutrients –eutrophication

B. Carbon oxygen cycle

carbon is the backbone of sugars – Carbo, protein, lipids , nucleic acids
oxygen is used to burn this sugar by most organisms
sugars are the energy source of choice for all living things
Carbon where is it found

a)CO2 0.038% of atmosphere

b)large reserves in the ocean 60X the atmosphere

c)also carbonate rocks- limestone

Carbon dioxide and the climate

carbon dioxide causes greenhouse effect

6. Primary productivity – photosynthesis

Carbon dioxide + water + sunlight---> glucose + oxygen

7. Cellular respiration takes in oxygen and sugar and releases energy +

carbon dioxide

Notice photosynthesis and cellular respiration are almost total reverse process

8. Decomposition – Breakdown of organic molecules releasing CO2

9. Sequester - Sedimentation

a. carbon materials locked in sedimentary rocks

b. Fossil fuels

c. calcium carbonate shells of aquatic organisms CaCO3

10. Combustion - burning fossil fuels

1)fossil fuels are dead organic matter (plant material) stored in the earth, coal, oil, and, natural gas

2)burning these releases carbon in the form of carbon dioxide

11. Man and the Carbon oxygen cycle

burning fossil fuel has greatly increased CO2 levels
deforestation
slash and burn agriculture burning rain forest increase CO2 and stops photosynthesis
Global warming
Sequestration discussions

C. The Nitrogen cycle

nitrogen is one of the four most important elements of life CHON
nitrogen forms an important part of all proteins

amino acids building blocks of proteins have NH2 Amino group
proteins are what help make up cell membranes, enzymes and many other molecules of biological importance

nitrogen is also building block of nucleic acids (DNA and RNA all living organisms genetic material)
Forms of nitrogen

nitrogen gas N2– 78% of atmosphere
ammonia NH3 + ammonium NH4+

1)toxic to most organisms

2)can be used by some plants

3)produced via excretion

nitrites/nitrates NO2-/ NO3-

1)used by plants

2)fertilizer

nitrogenous wastes- nitrogen compounds formed from the breakdown of protein

1)urea- urine

2)sweat and urine

3)changed to ammonia

The cycle three major inputs of nitrogen

-Nitrogen is found in air as N2 ( 78% of atmosphere)

-this is useless to all living things except bacteria

nitrogen fixationbacteria fix atmospheric into ammonia NH3

1)in soil- cyanobacteria

2)in root nodules- symbiotic relationship

a)legumes- 18,000 sp. beans, alfalfa, clover

b)planted as crop rotation

c)Rhizobium bacteria

lightning fixes nitrogen (10%) forms ammonia and enters nitrification pathway
industrial fertilizer production (produces nitrates as fertilizer)

nitrification ammonia changes by bacteria into nitrate ions NO3-

7. Food Chains

plants uptake nitrates and ammonia adding them to living material

8. Death, excretion, and decomposition

a. Ammonification – taking organic nitrogen compounds and

converting them to ammonia and ammonium

NH3 NH4+

b. Denitrification - nitrates are used by microorganisms and returned to

atmosphere as nitrogen gas ( called)

9. Major reactions

nitrogen fixation- atmospheric nitrogen to ammonia by bacteria
nitrification- ammonia to nitrites / nitrate for use by plants
ammonification- ammonia from decomposition and waste
denitrification- nitrates/nitrites back to nitrogen gas by bacteria nitrates used as energy source

10. Man and the nitrogen cycle

a. nitric oxide NO2 Nitric Acid HNO3 – fossil fuels acid rain

b. N2O – Nitrous oxide – Green house gas

c. NO3- - Nitrate – leaching into groundwater

d. Nitrogen compound eutrophication NPK – fertilizers

e. Haber-Bosch process  N2 gas + Methane  anhydrous

ammonium

- 100 million tons of nitrogen fixed

- 0.75 % of World’s energy use put into this proecess

.D. phosphorous cycle

importance of phosphorous

a)essential nutrient of plants

b)DNA RNA component

c)ATP ADP

d)phospholipids

e)component of teeth, bones, shells

f)80% of your teeth and bones – calcium phosphate

Sources of phosphorous

-Phosphate salts-

-PO43- Orthophosphate

-PO4 - Phosphate

a)terrestrial rocks sedimentary

b)shallow marine sediments

Phosphorous does not have atmosphere as source- Very little as phosphoric acid
cycle is slow because sedimentary rock must be created, uplifted and weathered to complete cycle
The cycle

a)phosphorous rich sedimentary rock reaches the surface and is weathered

b)this phosphorous is taken up by plants

c)passed along food chain

d)some phosphorous starting again in plants

e)some running off to become sediments again

Guano- Bird excrement- marine birds- build up large amounts of phosphorous from eating fish – Excellent fertilizer

Man and the phosphorous cycle

a)mining for fertilizer

b)ground bone meal for fertilizer

c)clear cutting rainforest for logging

1)Burning material to release phosphate

2)removing organic material removes source of phosphate

3)becomes limiting

d)addition of phosphates to water – Eutrophication

1)detergents

2)fertilizer

3)animal wastes

4)Sewage

5)algae bloom / fish kills

e) increased phosphate cycle 3.7 times

E. The Sulfur cycle

1) Sulfurs importance

- protein building block

2) Sources

a. Sulfur containing minerals

- Gypsum – CaSO4

- Pyrite – FeS2

b. Sulfate salts – SO4- - Ocean sediments + Salt spray

c. Hydrogen Sulfide – H2S - Swamps

d. Sulfur Dioxide – SO2– volcanoes

e. Dimethyl Sulfides – Marine algae produce add to atmosphere

3) Uptake

- Plants utilize sulfate salts

- moves through food chains

4) Cycling

- Many materials end up in atmosphere where they will form acid