Questions and Answers
What is the definition of an ecological community?
What do primary producers do?
Convert sunlight or inorganic molecules into chemical energy.
What are trophic levels?
'Food chains' or 'food webs'.
Higher trophic levels have more individuals than lower ones.
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What does the 2nd law of thermodynamics state about energy?
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Due to the 2nd law, only about 10% of energy is transferred from one trophic level to the next, with losses due to _____ .
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What is characteristic of pyramid diagrams in ecological communities?
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Higher productivity levels always lead to higher species diversity.
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How do interactions among species influence community services?
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Study Notes
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.
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Description
Test your knowledge of ecological communities and their interactions. This quiz includes key terms such as primary producers and the roles of different species in an ecosystem. Perfect for students studying ecology or environmental science.
