Ecosystems and Energy

Ecology

The study of interactions among organisms and their abiotic environment.

Biotic vs. Abiotic

Biotic is the living environment; abiotic is the nonliving physical environment.

Species

A group of similar organisms that freely interbreed to produce fertile offspring.

Population

Organisms of the same species living in the same area at the same time.

Community

All populations of different species that live and interact in an area.

Ecosystem

A biological community and its physical, abiotic environment.

First Law of Thermodynamics

Energy cannot be created or destroyed, only changed in form.

Second Law of Thermodynamics

Energy conversion results in some energy being degraded to heat.

Photosynthesis

Biological process of transforming solar radiant energy into chemical energy of carbohydrates (sugar) molecules.

Cellular Respiration

Process where chemical energy captured in photosynthesis is released within cells of plants and animals.

Autotrophs

Producers that manufacture their own food from inorganic materials.

Heterotrophs

Consumers that use the bodies of other organisms as food.

Decomposers

Organisms like fungi and bacteria that break down dead organic material. Release inorganic molecules (CO2 and nutrients) that producers can use. Present at all tropic levels

Gross Primary Productivity (GPP)

Total amount of energy plants capture and assimilate over time.

Net Primary Productivity (NPP)

Plant growth and available food after cellular respiration is subtracted.

An estuary

semi-enclosed body of water

Tidal

gradual changed from fresh to salt water

Landscape

Several interacting ecosystems (ex: bear hunting for salmon in a river, living in adjacent forest)

Biosphere

contains earth's communities,ecosystems and landscapes

Atmosphere

gaseous envelope surrounding earth

Hydrosphere

earth's supply of water

Lithosphere

soil and rock of the earths crust

Energy

ability or capacity to do work

Different types: Chemical, Thermal, Mechanical, Nuclear, Electrical, and Radiant/Solar

Potential energy (stored energy)

Kinetic energy (energy of motion)

Solar Radiation

The primary source of energy on planet Earth. Plants turn solar radiation into food

Thermodynamics

Study of energy and its transformations

System

The object being studied

Closed System

Does not exchange energy with surroundings (rare in nature)

Open System

Exchanges energy with surroundings

Chemosynthesis

Bacteria perform, similar to photosynthesis, but use chemical (H2S) not sunlight.

Energy Flow Through Ecosystems

Energy enters ecosystems from the sun

Flows linearly in one way direction through ecosystems

Energy exits as heat loss

First tropic level

Producers= autotrophs

Second tropic level

Primary consumers

Third tropic level

Secondary consumers

Fourth trophic level

Tertiary consumers

Omnivores

eat both plants and animals

Detritivores (Consumers of detritus)

Eat dead material such as leaves, carcasses, feces. Examples: shrimps, crabs, worms, millipedes, snails.

Food Web

Visualizes feeding relationships within a community. More complex than food chain Still simplified compared to nature.

Soil

Is alive, a complex web of biotic and abiotic interactions ensuring the survival of plants and animals, rather than just a mass of minerals.

Ecological Pyramids

Graphically represent the relative energy value of each trophic level. Large amount of energy is lost as heat between trophic levels

Pyramid of Numbers

Illustrates the number of organisms at each trophic level, where fewer organisms occupy each successive level. Does not indicate biomass of organisms at each level or the amount of energy transferred between levels

Pyramid of Biomass

Illustrates the total biomass at each successive trophic level measures the total amount of living material

~90% reduction in biomass through trophic levels

100 to 10

Pyramid of Energy

Illustrates how much energy is present at each trophic level and how much is transferred to the next level

Most energy dissipates between trophic levels

Lost as heat and energy to maintain each level explains why there are so few trophic levels

Ecosystem Productivity

Net Primary Productivity (plant growth per area per time) = Gross Primary Productivity (total photosynthesis per area per time) - Plant Cellular Respiration (per area per time)

Variation in NPP by Ecosystem

Humans consume a large amount of global NPP

~30% but we make up ~0.5% of biomass

This represents a threat to planet's ability to support both human and non-human inhabitants