Community Ecology Pt 2

All ecosystem have two key properties:

Energy flows though them in one direction, whereas matter cycles within them.

Energy enters most ecosystems as

Sunlight

Light energy

Is converted to chemical energy by autotrophs, passed to heterotrophs in the organic compounds of food, and and dissipated as heat.

An ecosystem

Requires a continuous influx of energy from an external source.

In chemical cycling,

Elements are passed between living and non-living components of the ecosystem

Photosynthetic and chemosynthetic organisms

Take nonliving components of the ecosystem in inorganic form and incorporate them into organic compounds.

Elements are

Returned in inorganic form tot he environment by organic waste breakdown by metabolism and dead organisms by decomposers

1st law of Themodynamics

Energy cannot be created or destroyed - just transferred or transformed

Every exchange of energy

Increases the entropy of the universe

Conservation of Mass

Matter Cannot be created or destroyed

Detritus

Nonliving organic material

Decomposers

Convert organic matter from all tropic levels to inorganic compounds usable by primary producers

In most ecosystems

The amount of light energy converted to chemical energy - in the form of organic compounds usable- by photoautotrophs during a given time period is the ecosystem’s primary production

In ecosystems, whether the producers are chemoautotrophs,

The initial energy energy impact is chemical, and the initial products are the organic compounds synthesized by the the chemoautotrophic microorganisms.

Only a small fraction of the sunlight reaching Earth’s surface __________, and only 1% of visible light striking photosynthetic organisms is ___________

Is used in photosynthesis; converted to chemical energy

Gross Primary Production (GPP)

Amount of energy from light/chemical converted to the chemical energy of organic molecules per unit item

Net Primary Production (NPP)

GPP - Ra (energy used for cellular respiration); J/m² * yr or g/m² * yr

Net Ecosystem Production (NEP)

A measure of the biomass accumulation by proceeds and consumers during that time; determines whether an ecosystem in gaining or losing carbon over time; GPP - RT (total respiration of all organisms in the system)

The most common way to estimate NEP

Is to measure the net flux (flow) of CO2 or O2 entering/ leaving the ecosystem

A limiting nutrient

Is the element that must be added for production to increease

Areas of upwelling, where deep, nutrient-rich waters

Rise to the ocean surface, have high primary production

The amount of chemical energy i consumer’s food converted to new biomass during a given period

Is called the secondary production of the ecosystem

Production efficiency

Percentage of energy stored in assimilated food used for growth and reproduction: (Net secondary production * 100%)/(Assimilation of primary production)

Trophic efficiency

Is the percentage of producing transferred from one tropic levels to the next; range is from 5-20% averaging 10%

The progressive loss of energy alone a food chain

Limits the abundance of top-level carnivores an ecosystem can support

Biomass pyramids

Represent total dry mass off all organisms per trophic level

Inorganic compounds

are taken up by autotrophs and transformed into biomass

Organic Compounds

Are transformed to heterotrophs as food

Inorganic compounds

Are release through metabolism and decomposition

Ecosystems

Are open system, exchanging energy and matter with its surroundings

Entropy

Is an indicator of the amount of energy in a system that is no longer available for additional work; it measures the amount of dispersion of heat in a thermodynamic system

Energy enters

As solar radiation and transformed into chemical energy by photosynthetic organisms

Primary production

Light energy converted to chemical energy by photoautotrophs during a period of time

Secondary Production

The amount of chemical energy in food converted to new biomass during a period of time

On average,

NPP is ~ ½ of GPP

NPP

Is not total biomass of photosynthetic autotrophs present - it is the amount of new biomass added in a given period of time

In terms in NPP

Tropical rain forests , estuaries, and coral reef are among the most productive

Open oceans

Are relatively unproductive but contribute much to global NPP due to size

When an organism dies,

The atoms in its body are returned to the atmosphere, water, or soil by decomposers

By liberating nutrients from organic matter,

Decomposition replenishes the pools of inorganic nutrients that plants and other autotrophs use to build new organic matter.

When an organisms dies,

The atoms in its body are returned to the atmosphere, water, or soil by decomposers.

By liberating nutrients from organic matter,

Decomposition replenishes the pods of inorganic nutrients that plants and other autotrophs use to build new organic nutrients

Decomposers

Are heterotrophs; they get their energy from detritus, and their growth is controlled by the same factors that limit primary production in ecosystems, including temperature, moisture, and nutrient availability

Decomposers typiclly

Grow faster and decompose material more quickly in warmer ecosystems.

Decomposition on land

Is also slower when conditions are either too dry to decompose to thrive or too wet to supply them with enough oxygen

In aquatic ecosystems,

Deep water below the photonic zone usually contain nigh levels of nutrients, since organisms that sink there ae decomposed yet there are no photosynthetic organisms to use up nutrients.

Process that bring deep water to the surface, such as seasonal mixing or wind-driven upwelling of deep water,

Boost primary production in surface waters

Larger rivers

Carry a large amount of nutrients from terrestrial ecosystems to the coastal

Biochemical cycles

Any of the various chemical cycles involving both biotic (local Global) and abiotic components of ecosystems

Gaseous forms

Of Carbon, Oxygen, Sulfur, and Nitrogen, occurs in atmosphere, and cycles of these elements are essentially global

Other elements, like phosphorous, potassium, and calcium

are too heavy to occur as gases at Earth’s surface. They cycle locally in terrestrial ecosystems and more locally in aquatic ecosystems