8.2 Energy Flow Through Ecosystems

Ecological levels

species→population→community→ecosystem→biome→biosphere

Ecosystem

the sum of all the organisms living in a given area and the abiotic factors they interact with

Biotic

living or once living components of an environment

Abiotic

nonliving (physical and chemical properties of the environment)

Gain/Loss of Energy

a net gain in energy results in energy storage or growth of an organism

a net loss in energy results in loss of mass and eventual death of an organism

Metabolic Rate

the total amount of energy an animal uses in a unit of time

can be measured in calories, heat loss, or by the amount of oxygen consumed (or CO2 produced because it is a byproduct of cellular respiration)

An animal’s metabolic rate is related to its body mass

smaller= higher metabolic rate

larger= lower metabolic rate

Endotherms

use thermal energy from metabolism to maintain body temperatures

ex. mammals

Ectotherms

use external sources (ex. sun/shade, other organisms) to regulate their body temperature

ex. reptiles

Trophic Levels

species can be grouped into trophic levels based upon their main source of nutrition and energy

unlike mass, energy CANNOT be recycled, the sun constantly supplies energy to ecosystems

Primary Producers (autotrophs)

use light energy to synthesize organic compounds

ex. plants, algae, photosynthetic plankton

some organisms use chemosynthetic (vs photosynthetic) meaning they produce food using the energy created by chemical reactions ex. bacteria and archaea

Heterotrophs

rely on autotrophs because they can’t make their own food

includes all types of consumers

some organisms are omnivores (like humans) that feed at several trophic levels simultaneously

Primary Consumers

herbivores

Secondary Consumers

carnivores that eat herbivores

Tertiary Consumers

carnivores that eat other carnivores

Quaternary Consumers

carnivores that eat tertiary consumers

if they have no natural predators, they are known as apex predators

Scavengers

animals that consume dead/decaying organisms (plants or animals)

Decomposers

small organisms (like bacteria and fungi) that get energy from detritus produced at other tropic levels

important for recycling chemical elements

decomposers reduce organic material to small inorganic molecules that producers can take in

Detritus

nonliving organic material

ex. leaves, wood, dead organisms

Food Chain

the transfer of food energy up the trophic levels

Food Webs

linked food chains

Energy in Trophic Levels

any changes to the availability of energy can disrupt ecosystems

ex. a change at the producer level can affect the number and size of the remaining trophic levels

Primary Production

the amount of light energy that is converted into chemical energy

primary producers set a “spending limit” for the entire ecosystems energy budget

gross primary production (GPP): total primary production in an ecosystem

net primary production (NPP): GPP - energy used by primary producers for respiration

Secondary Production

the amount of chemical energy in a consumer’s food that is converted to new biomass

the transfer of energy between trophic levels is around 10% efficiency

Matter Cycling

unlike energy, matter cycles through ecosystems

matter is found in limited amounts, unlike solar energy

includes biogeochemical cycles

Biogeochemical Cycles

nutrient cycles that contain both biotic and abiotic factors

water, carbon, nitrogen, and phosphorous cycles

Water Cycle

water is essential for all life and influences the rate of ecosystem processes

Carbon Cycle

carbon is essential for life and required in the formation of organic compounds

Nitrogen Cycle

nitrogen is important for the formation of amino acids, proteins, and nucleic acids

Phosphorous Cycle

phosphorous is important for the formation of nucleic acids, phospholipids, and ATP