Ecosystem Dynamics

original source of energy

Sun

1st Law of Thermodynamics

“Energy cannot be created or destroyed”

Energy input must be continuous

Energy is converted to chemical energy stored in food

2nd Law of Thermodynamics

“Every exchange of energy increases entropy”

Energy conversion is inefficient: some is lost as heat as it transfers through ecosystems

Law of Conservation of Mass

“Matter cannot be created or destroyed”

Nutrient inputs must equal outputs

Chemicals/atoms are continuously recycled through the ecosystem

trophic levels

any step in a nutritive series, or food chain, of an ecosystem, organised on the basis of feeding behavior

primary producers

photosynthesis; autotrophs

ie. plants, bacteria

Trophic efficiency

percent of energy transferred from one level to the next

10% passes on to next level; 90% released as heat

primary consumers

eat primary producers; heterotrophs

e.g. herbivores

secondary consumers

eat primary consumers; heterotrophs

e.g. carnivores, insectivores, piscivores

tertiary consumers

eat secondary consumers; heterotrophs

e.g. carnivores, insectivores, piscivores

apex consumer/predator

highest link in energy cycle; is not eaten/preyed on by any other consumer

decomposers

take leftover energy and matter from dead producers/consumers and return to environment

conservation of matter

no matter is lost; may be changed in form but atoms in = atoms out

biogeochemical cycles

cycles that involve molecules that are essential for life and how they circulate through an ecosystem/biosphere

ex. carbon, nitrogen, phosphorus, water

water cycle

recycling of all water in the biosphere since it is essential to all life

ie. precipitation and evaporation

carbon cycle

recycling of all carbon in the biosphere for organic molecules & energy (storage)

ex. photosynthesis and cellular respiration, sediments & rock

nitrogen cycle

recycling of all nitrogen in the biosphere - essential component of amino acids, proteins, & DNA

Plants can use ammonium (NH4+) & nitrate (NO3-)

Animals can only use organic forms of nitrogen (amino acids)

ex. air (80% atmosphere); fixation in soil

phosphorous cycle

recycling of all phosphorus in the biosphere - main component of nucleic acids, phospholipids, and ATP - local

ex. Marine sedimentary rocks, organisms, ocean, and soi

evaporation

water molecules go from liquid to gaseous state

water vapour

gaseous water

condensation

water vapour returns to liquid droplets/solid cyrstals in the sky to form clouds

precipitation

water falling from cloud onto land or body of waterr

river

stream of flowing water; forms from runoff from precipitation

sublimation

ice/snow to vapourtr

transpiration

evaporation of water from the surface of plants

freshwater

water with minimal ionic solutes; 2.5% of total water on planet, 68.9% of which is in glaciers, 30.8% in groundwater, and 0.3% in lakes and rivers

Average residence time for water molecules

gross primary production (GPP)

total amount of energy acquired by primary producers (via photosynthesis or chemosynthesis) in an ecosystem; total amount of energy converted to organic molecules over time

net primary productivity (NPP)

remaining usable amount of energy transmitted out of a producer after metabolic processes, heat, etc.; amount of stored energy available to consumers

NPP = GPP - Ra

Primary Productivity in Aquatic Systems

light penetration, nutrient availability, micronutreients (minerals)

Primary Productivity in Terrestrial Systems

driven by climate and vascular plants; temperature, moisture, nutrients

Respiration by autotrophs (RA)

amount of energy used by photosynthesizing organisms (~1/2 of GPP)

high productivity/NPP ecosystems

warm temperatures, high humidity and an influx of nutrients

ex. tropical wet rainforests and estuaries

low productivity/NPP ecosystems

dry and either too hot or too cold for high rates of plant growth

ex. deserts and the Arctic

Net Ecosystem Production (NEP)

amount of biomass accumulated by producers & consumers; tells us if the ecosystem is gaining or losing carbon over time

NEP = GPP - Rt

Respiration by producers and consumers (Rt)

amount of energy used by ALL organisms in the ecosystem

Carbon sinks

NEP > 0 ; net storage of carbon

Carbon sources

NEP < 0; losing more carbon than is being stored in plants and animals

Secondary production

amount of energy from food converted into new biomass

Production Efficiency

percentage of energy from food used for growth and reproduction but not respiration; inversely related to energy demands

Biomass pyramids

Shows how much BIOMASS is in each trophic level; can be inverted if there is exceptionally high turnover (consumption)

Upwelling

brings nutrients from deeper water to the surface

eutrophication

excessive influx of nutrients from agricultural runoff can cause exponential growth in algal and phytoplankton populations, depleting the water of oxygen, and negatively affecting the aquatic flora and fauna

Food chain

Linear sequence of consumers, producers, and detritovores (who eats whom); Primary productivity and Loss of energy between trophic levels limits food chain length (<5 links)

Food web

A network of interconnected food chains