Ecosystem Ecology: Production and Energy Flow

Definition of the first law of thermodynamics

Energy can be changed from one form to another, but it cannot be created or destroyed

What are the two main forms of autotrophy?

Photosynthesis and chemosynthesis

Definition of photosynthesis

Process by which plants, algae, and cyanobacteria convert carbon dioxide into organic compounds, using energy from sunlight

Definition of chemosynthesis

The process by which eubacteria and archaea convert carbon dioxide (or other inorganic carbon molecules such as methane) into organic compounds, using energy from the oxidation of other molecules

Definition of primary production

Amoun of energy captured by autotrophs through photosynthesis and chemosynthesis; initial fixation of inorganic materials into organic materials

What is the currency of primary production?

Carbon

Definition of primary productivity

Rate of primary production

Definition of gross primary production (GPP)

Total amount of carbon fixed by the autotrophs in an ecosystem

What contributes to a terrestrial ecosystem’s GPP?

Photosynthesis and leaf area index (LAI)

Definition of leaf area index (LAI)

Leaf area of plants relative to surface area of the ground

Definition of net primary production (NPP)

GPP-respiration of the amount of biomass gained by plants through photosynthesis

Definition of CO2 uptake

What amounts of CO2 are being used to make carbs

Why is NPP an approximate value?

Tells photosynthetic growth area and not root growth area

How can NPP be estimated in a terrestrial ecosystem?

Remote sensing of chlorophyll signature, net ecosystem exchange (NEE) of carbon dioxide

Why is it difficult to measure NPP in aquatic ecosystems?

Phytoplankton have a high turn-over rate

How can NPP be measured in aquatic ecosystems?

Remote sense of chlorophyll, comparing CO2 concentrations in water samples incubated in the light vs dark

What increases NPP in a terrestrial ecosystem?

Temperature and water availability

What results in a difference of NPP between ecosystems?

Function of species composition; species that have evolved in resource-poor environments tend to be slow-growing

What controls NPP in an aquatic ecosystem?

Nutrient availability such as availability of phosphorus, nitrogen, and/or iron, water clarity

What does the addition of phosphorus promote in bodies of water?

More algae growth

How do plants allocate growth depending on NPP?

Depending on the nutrients available, plants can grow different areas when that needed growth nutrients is abundant

Definition of secondary production

Energy obtained by heterotrophs through the consumption of organic compounds produced by other organisms

How are heterotrophs classified?

By their diets

What are the different types of heterotrophs?

Herbivores, carnivores, detritivores, omnivores

How do researchers detect how organisms make a living?

Examining their isotopic compositions

Equation for net secondary production

(ingestion-respiration)-egestions

Definition of egestion

What is leaving an organism’s body, does not benefit in generation of energy

How does net secondary production differ between aquatic and terrestrial ecosystems?

Net secondary production is a larger fraction of NPP in aquatic ecosystems than terrestrial ones

What types of species account for the majority of net secondary production?

Detritivores

What does more primary production result in?

The more primary production an environment does, the more herbivores that same environment should be able to support

Equation of net ecosystem exchange (NEE)

GPP-total ecosystem respiration

Definition of net ecosystem exchange (NEE)

Total amount of growth in an ecosystem

Definition of total ecosystem respiration

Takes plant and heterotroph respiration into account

What is the relationship between NEE and NPP?

NPP=NEE-heterotrophic respiration

How does energy move through an ecosystem?

Trophic interactions of who eat who in an environment

How do functional groups relate to nutrient intake?

Functional groups take in nutrients in a similar way (cougars and scorpions are both predators and gain their energy through similar methods)

How are functional groups categorized?

Trophic level and guilds

Definition of trophic level

Number of feeding steps away an organism is from the autotroph

Definition of guild

Group of species that exploit the same class of environmental resources in a similar way

Definition of autochthonous inputs

Most energy comes from autotrophs within the system

Definition of allochthonous inputs

Some energy arrives as external inputs (leaf litter in a stream)

What input systems do aquatic and terrestrial systems follow?

Terrestrial systems are autochthonous; aquatic systems are allochthonous

What ecosystem often has more detritus?

Terrestrial ecosystems

Which ecosystem has a larger biomass for primary producers?

Terrestrial ecosystems

Why are trophic pyramids of energy pyramid-shaped?

There is a loss of energy at each step of the pyramid as they go up due to entropy

Why are trophic pyramids of biomass often inverted for aquatic systems?

Their primary producer biomass is much smaller (algae) than terrestrial primary producers (trees)

Definition of the 10% rule

90% of energy is given off as heat, while 10% of energy goes up to the next trophic level

What type of system is energy?

One-way, open system

Why are herbivores less successful at consuming autotrophs on land than at sea?

Predation keeps herbivore populations low, plants in energy-rich environments are strongly defended against herbivores, phytoplankton are better food than plants

Definition of trophic efficiency

Ration of energy in one trophic level to energy in preceding trophic levels

What are factors that determine energy flow between trophic levels?

Consumption efficiency, assimilation efficiency, production efficiency

Definition of consumption efficiency

Proportion of available energy consumed

Definition of assimilation efficiency

Proportion of food energy assimilated

Definition of production efficiency

Proportion of assimilated energy converted to biomass

Definition of bottom-up control

Nutrients control the system through primary production

Definition of top-down control

Secondary carnivores/tertiary consumers control the system

How is the type of control determined in a system

Depends on the organisms in the system for how it’s controlled

Definition of trophic cascade

Changes in abundance or species composition at a higher trophic level have strong effects throughout lower levels

What are factors often left out of food webs?

Detritus and detritivores are often ignored, symbiotic relations are often ignored, omnivores eat at multiple trophic levels, organisms may change trophic levels as they age

How are food webs a useful tool even though they are simplified?

Useful for identifying ecological interactions that may be most important for structuring ecosystems

Definition of interaction strength

The effect of one species’ population on the size of another species’ population; typically measured by single species removal

Definition of keystone species

A species with an effect on its community or ecosystem disproportionate to its own abundance

Definition of bioaccumulation

The increasing concentration in the body over an organism’s life span of pollutants that can’t be metabolized or excreted (mercury)

Definition of biomagnification

The increasing concentration in the bodies of organisms at higher trophic levels of pollutants that can’t be metabolized or excreted

What’s a simple way to remember the difference between bioaccumulation and biomagnification?

Bioaccumulation is at the individual level; biomagnification looks at an entire food chain/web

Definition of teratogen

Term used to describe something that causes developmental effects

Definition of ecological footprint

The amount of productive land a person is using to live in terms of energy, food, etc.; how a person affects biodiversity