Topic 6: Ecosystems & Landscapes

Trophic Pyramid

A chart composed of stacked rectangles representing the amount of energy or biomass in each trophic group

Pyramid of Energy

A trophic pyramid that displays the total energy existing at each trophic level

Pyramid of Biomass

A trophic pyramid that represents the standing crop of organisms present in different trophic groups

terrestrial pyramids of energy & biomass

pyramids of energy and biomass have similar shapes because most of the energy and most of the standing biomass are found in the producers

aquatic pyramids of energy & biomass

• most of the energy is still found in the producers, but these producers are primarily tiny algae that do not live very long because they are rapidly consumed by herbivores

• this continual rapid consumption results in a large biomass of consumers in these systems

Primary Production

• The rate at which solar or chemical energy is captured and converted into chemical bonds by photosynthesis or chemosynthesis

• tells us how much energy is available in an ecosystem

Gross Primary Productivity (GPP)

The rate at which energy is captured and assimilated by producers in a given area

Net Primary Productivity (NPP)

The rate at which energy is assimilated by producers and converted into producer biomass in a given area

Remote Sensing

A technique that measures conditions on Earth from a distant location, typically using satellites or airplanes that take photographs of large areas of the globe

3 ways to measure primary producitivity

• the change in the biomass of producers over time

• the movement of carbon dioxide over time

• the movement of oxygen over time

Secondary Production

the generation of new biomass by heterotrophic organisms (consumers) in an ecosystem

Egested Energy

The portion of consumed energy that is excreted or regurgitated

Assimilated Energy

The portion of energy that a consumer digests and absorbs

Respired Energy

The portion of assimilated energy a consumer uses for respiration

Net Secondary Production

The rate of consumer biomass accumulation in a given area

Consumption Efficiency

The percentage of energy or biomass in a trophic level that is consumed by the next higher trophic level

Assimilation Efficiency

The percentage of consumed energy that is assimilated

Net Production Efficiency

The percentage of assimilated energy that is used for growth and reproduction

Ecological Efficiency (food chain efficency)

The percentage of net production from one trophic level compared to the next lower trophic level

Describe/list what happens to the energy incorporated into in a trophic level that is not used for production at the next trophic level

• used for the organism's metabolism, lost as heat, or remains in undigested food

• when energy is transferred from one trophic level to the next in a food chain, only about 10% of the energy is passed on

Describe the relationship between ecological efficiency and the number of trophic levels in aquatic vs terrestrial ecosystems

• aquatic ecosystems typically have more trophic levels than terrestrial

  ecosystems

• terrestrial producers have more defenses

  • there is low consumption efficiency in terrestrial ecosystems, so a large fraction of the producer biomass ultimately becomes detritus

• aquatic ecosystems are composed primarily of unicellular algae that contain fewer defenses and are relatively easy for herbivores to digest

Hubbard Brook Experimental Forest

• researchers removed all the trees from an entire watershed and sprayed it with herbicides for several years to suppress plant growth

  • as a control, adjacent watersheds were not logged

• without plants to take up water and nutrients, the movement of elements in the ecosystem changed dramatically

Landscape Ecology

The field of study that is focused on the spatial arrangement of habitats at different scales and how this influences individuals, populations, communities, and ecosystems

Habitat Fragmentation

the process of breaking up large, continuous habitats into smaller, isolated patches

Edge Effect

changes in the physical and biological environment at the boundary of a habitat fragment

Edge Specialist

species that thrive in areas where two different habitat types meet

Habitat Corridor

A strip of favorable habitat located between two large patches of habitat that facilitates dispersal

Stepping Stones

Small intervening habitat patches that dispersing organisms can use to move between large favorable habitats

the relationship between landscape ecology and habitat fragments

landscape ecology providing the framework for understanding how spatial patterns, including habitat fragments, affect ecological processes