Ecology: Primary Production and Efficiency

Study Notes

Compensatory Growth and Grazing

Moderate grazing can increase plant productivity due to compensatory growth, where plants respond to grazing by increasing their growth rate.

Species Richness and Primary Production

Species richness of primary producers (plants, algae) influences primary production, with evidence showing that higher species richness leads to greater primary production.
This is because a diverse range of species can exploit different resources and occupy different niches, resulting in more efficient use of resources.

Primary Production and Species Richness

Primary production can be greater with higher species richness of primary producers because diverse species can:
- Utilize different resources and exploit different niches
- Increase the efficiency of resource use
- Enhance ecosystem stability

Ecological Efficiency

Ecological efficiency is the percentage of energy transferred from one trophic level to the next.
It is typically low, ranging from 5-20%, due to energy losses during trophic transfers.

Secondary Productivity

Secondary productivity is the rate of biomass production of heterotrophic organisms, such as consumers and detritivores.

Bottom-Up Control of Secondary Production

Research has demonstrated that primary production can control secondary production through bottom-up effects, where changes in primary production influence the availability of resources for secondary producers.

Trophic Vocabulary

Key terms:
- Primary producer: autotroph that produces its own food through photosynthesis
- Autotroph: organism that produces its own food through photosynthesis
- Photosynthesis: process of converting light energy into organic compounds
- Secondary producer: heterotroph that consumes other organisms to obtain energy
- Consumer: heterotroph that consumes other organisms to obtain energy
- Heterotroph: organism that obtains energy by consuming other organisms
- Herbivore: consumer that eats plants
- Detritivore: consumer that eats dead organic matter
- Predator/Carnivore: consumer that eats other animals

Equations for Primary Production and Respiration

Photosynthesis equation: 6CO2 + 6H2O + light energy → C6H12O6 (glucose) + 6O2
Respiration equation: C6H12O6 (glucose) + 6O2 → 6CO2 + 6H2O + ATP

Ecosystem Metabolic Processes

Gross primary productivity (GPP): total rate of photosynthesis
Net primary productivity (NPP): GPP - Rp (autotrophic respiration)
Autotrophic respiration (Rp): energy used by autotrophs for maintenance and growth
Heterotrophic respiration (Rh): energy used by heterotrophs for maintenance and growth
Ecosystem respiration (Re): total energy used by ecosystem for maintenance and growth
Net ecosystem productivity (NEP): NPP - Re

Relations between Ecosystem Metabolic Processes

NEP = GPP - Re
NPP = GPP - Rp

Partitioning of GPP

A percentage of GPP is allocated to Rp (autotrophic respiration)
The remaining percentage is allocated to NPP

Influence of Climate on Primary Production

Climate influences primary production, with evidence showing that changes in temperature, precipitation, and other climate factors affect primary production.

Influence of Plant Growth Form on Primary Production

Plant growth form, such as leaf area, influences primary production, with evidence showing that variations in leaf area affect primary production.

Limiting Nutrient

A limiting nutrient is a nutrient that restricts the growth of organisms when it is scarce.
Research evidence, such as nutrient addition experiments, can be used to identify which nutrient is limiting in a particular ecosystem.

Nutrient Limitation in Aquatic Ecosystems

Nitrogen (N) typically limits primary production in lakes and rivers
Phosphorus (P) typically limits primary production in estuaries and oceans

Description

Test your understanding of ecological concepts, including the impact of grazing on plant productivity, the relationship between species richness and primary production, and the definition of ecological efficiency. Get ready to dive into the world of ecology and explore the intricate relationships between species and their environments.

Ecology: Primary Production and Efficiency

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Questions and Answers

What is the effect of moderate grazing on plant productivity in reference to compensatory growth?

Why is primary production often greater with a higher species richness of primary producers?

What is the main reason ecological efficiency is typically low, ranging from 5-20%?

What is secondary productivity?

What is the primary mechanism demonstrated by research to control secondary production?

What is the process by which autotrophs produce energy from sunlight?

What is the term for the nutrient that limits primary production in an ecosystem?

What is the difference between gross primary productivity (GPP) and net primary productivity (NPP)?

What is the relationship between ecosystem respiration (Re) and net ecosystem productivity (NEP)?

What is the effect of plant growth form on primary production?

What is the typical limiting nutrient for primary production in aquatic ecosystems such as lakes and oceans?