Ecological Community Flashcards

Ecological Community

• A collection of species that coexist and interact within a defined spatial area.
• Each species has distinct interactions with other members of the community.
• Communities are studied based on energy dynamics and biomass.
• Size and scope can greatly vary; definitions can be precise or arbitrary.
• The number of species present is determined by the availability of energy resources.

Primary Producers

• Organisms that transform sunlight or inorganic molecules into chemical energy.
• Also known as autotrophs; they produce energy-rich organic molecules.
• Serve as a food source for heterotrophs (consumers).

Trophic Levels

• Comprise the structural layers in food chains or webs.
• Gross Primary Production (GPP) refers to the total stored chemical energy generated through photosynthesis.
• Not all GPP is accessible to consumers; some is utilized by producers for metabolic functions, with Net Primary Production (NPP) being available for consumption.

Higher Trophic Levels and Fewer Individuals

• In accordance with the second law of thermodynamics, roughly 10% of energy from one trophic level is transferred to the next level.
• This concept underscores ecological efficiency and energy loss.

Second Law of Thermodynamics

• States that the total amount of energy remains constant; however, energy transformations result in losses.
• Energy losses occur during conversions to different formats, impacting accessibility.

Energy Transfer Losses

• Energy transfer inefficiencies result from heat losses, availability issues, and digestibility challenges.
• Not all consumed energy is digestible or equitably accessed due to varying body compositions across species.

Pyramid Diagrams

• Most ecological communities typically feature 3 to 5 trophic levels, constrained by energy losses at each stage.
• Populations at higher trophic levels tend to have lower reproductive rates and smaller numbers, but larger body sizes.
• Forest biomass mostly remains indigestible, supporting fewer consumers compared to more digestible marine algae, which can sustain larger populations.

Productivity and Species Richness

• The energy availability, particularly sunlight, is a limiting factor in productivity.
• Increased water availability typically results in higher productivity.
• While high productivity encourages greater species diversity, excessively high levels may lead to a decline in diversity due to competitive exclusion among species.

Interactions Among Species and Community Services

• Species interactions can lead to trophic cascades, where one consumer’s actions indirectly affect multiple other species.
• For example, in Yellowstone National Park, overgrazing led to erosion and decreased populations of riparian tree species such as willows and poplars.