Energy Flow and Nutrient Cycling in Ecosystems

Energy flow through ecosystems

Energy flows in a one-way direction: sunlight → producers → consumers → lost as heat.

Nutrient movement through ecosystems

Nutrients cycle through biotic and abiotic components, allowing for reuse within the ecosystem.

Non-cyclic energy flow

Energy flow is considered non-cyclic because energy is lost as heat at each trophic level and cannot be reused by the ecosystem.

Cyclic nutrient cycling

Nutrient cycling is cyclic because nutrients are recycled through processes like decomposition, allowing them to be reused indefinitely unless removed by external factors.

Major pools in the carbon cycle

Atmosphere (CO₂), terrestrial biomass, soil organic matter, oceans, and fossil fuels.

Major fluxes in the carbon cycle

Photosynthesis, respiration, decomposition, combustion, and ocean-atmosphere exchange.

Human influence on the carbon cycle

Humans influence the carbon cycle through fossil fuel burning, deforestation, and land-use changes.

Major pools in the nitrogen cycle

Atmosphere (N₂), soil (ammonium, nitrate), biomass, and sediments.

Processes in the nitrogen cycle

Nitrogen fixation, ammonification, nitrification, and denitrification.

Nitrogen fixation

Bacteria and some fungi convert atmospheric N₂ into biologically available forms.

Human influence on the nitrogen cycle

Humans influence the nitrogen cycle through synthetic fertilizers, fossil fuel combustion, sewage runoff, and altered nitrogen deposition patterns.

Major pools in the phosphorus cycle

Rocks/minerals, soil, biomass, and sediments.

Major fluxes in the phosphorus cycle

Weathering of rocks, uptake by plants, movement through food webs, decomposition, and sedimentation.

Human influence on the phosphorus cycle

Humans influence the phosphorus cycle through mining for fertilizers, agricultural runoff, and wastewater discharge.

Decomposition

The breakdown of dead organic matter by decomposers, releasing nutrients back into the ecosystem.

Lignin and decomposition

Lignin is a tough plant compound that resists decay, slowing decomposition; only specialized organisms can break it down.

Mineralization

The microbial conversion of organic nutrients into inorganic forms that plants can absorb.

Factors affecting decomposition

Temperature, moisture, oxygen availability, organic matter quality, and microbial community composition.

Ecological succession

The gradual process of change in species composition, structure, and ecosystem function over time.

Primary succession

It begins in areas with no soil and no previous life, such as after volcanic eruptions or glacier retreats.

Secondary succession

It begins in areas where soil is present but vegetation was removed, such as after fires or farming.

Chronosequence

A set of sites representing different ages or stages of succession, used to study ecological changes over time.

Geographic ecology

The study of ecological patterns and processes over large geographic scales.

Global patterns of biodiversity

Species richness is highest near the equator and decreases toward the poles; biodiversity hotspots include tropical rainforests and coral reefs.

Hypotheses explaining latitudinal variation in species richness

Productivity, environmental heterogeneity, climate stability, niche differentiation, and evolutionary rates.

Factors influencing species richness on islands

Island size, distance from the mainland, immigration and extinction rates, isolation, and habitat diversity.

Conservation biology

The study of how to conserve biodiversity, including protection, maintenance, and restoration efforts.

Indicator species

A species that reflects the health of an ecosystem, often sensitive to environmental changes.

Umbrella species

A species whose conservation indirectly protects many other species due to its large habitat requirements.

Landscape ecology

The study of spatial patterns and ecological processes across different scales in space and time.

Patches in landscape ecology

Homogeneous areas that differ from their surroundings within a matrix.

Edge-area (P/A) ratio

A measure of patch shape complexity; higher ratios indicate more edge relative to area.

Edge effect

The different environmental conditions and ecological processes that occur at the boundary of two ecosystems compared to their interiors.

Role of corridors in landscapes

They connect habitat patches, facilitating movement, gene flow, and biodiversity conservation.

Evidence for global climate change

Rising temperatures, extreme weather events, melting glaciers, sea-level rise, and ocean acidification.

Causes of global climate change

Greenhouse gas emissions, deforestation, and industrial activities.

Consequences of global climate change

Ecosystem disruption, threats to human health and food security, and economic impacts.

Land use/land cover change (LULCC)

Changes in the physical land type and how it is used by humans, affecting ecosystems and human populations.

Invasive species

Non-native organisms introduced to an ecosystem that cause harm to the environment, economy, or human health.

Problems caused by invasive species

They outcompete native species, alter habitats, introduce diseases, and disrupt ecological relationships.

Ecosystem services

Benefits humans obtain from ecosystems, categorized into provisioning, regulating, supporting, and cultural services.

Provisioning services

Material benefits from ecosystems, such as food, water, timber, and medicinal plants.

Regulating services

Benefits obtained from the regulation of ecosystem processes, like climate regulation and disease control.

Supporting services

Services that support other ecosystem services, including nutrient cycling and soil formation.

Cultural services

Non-material benefits from ecosystems, such as recreation, aesthetic value, and spiritual significance.