Matter, Energy, and Dynamics in Ecosystems
Matter and Energy in Ecosystems
In ecosystems, energy is transferred between organisms through trophic relationships.
Energy Flow
Energy flow is a unidirectional, open process. Ecosystems require a continuous energy supply for function. Energy enters ecosystems primarily from the sun. Producers use a small portion of solar energy reaching Earth to perform photosynthesis, converting light energy into chemical energy. Only the energy stored in organic matter transfers to the next trophic level.
Matter Cycling
Matter cycling is a closed, cyclic process. Matter circulates between living organisms, the atmosphere, water bodies, and the Earth’s crust in terrestrial ecosystems. Matter is constantly recycled. Producers use inorganic matter and convert it into organic matter.
Biomass and Production
Biomass is the amount of organic matter accumulated in an individual, trophic level, or ecosystem. It’s measured in units like kilograms or grams per surface area or volume.
Production
Production is the amount of energy stored as biomass at each trophic level per unit of time.
Types of Production
- Primary production: The energy captured by producers through photosynthesis.
- Secondary production: The energy captured by consumers through feeding.
Gross and Net Production
- Gross production (GP): The total amount of biomass generated by a trophic level.
- Net production (NP): The amount of biomass remaining available for the next trophic level.
Productivity
Productivity expresses the efficiency of a trophic level, relating its production to biomass. Higher productivity occurs with lower biomass loss between trophic levels.
Natural Changes in Ecosystems
Ecosystems are dynamic structures that change over time. They tend towards a state of equilibrium or stability with minimal changes.
Conditions for Stability
- Stable environmental factors.
- Relatively constant population sizes.
- Absence of external factors altering the ecosystem.
Types of Changes
- Natural changes: Result from the ecosystem’s internal dynamics.
- Artificial changes: Caused by human activities.
Duration of Changes
- Gradual changes: Occur slowly over long periods.
- Catastrophic changes: Happen quickly in a short period.
Natural changes affecting biocenosis occur over various time scales: biological (hundreds of years) and social (shorter periods).
Global Change
Throughout Earth’s history, abrupt global changes have affected the entire planet. Glacial periods covering large land areas are an example.
Rhythmic Changes
Ecosystems experience cyclical and predictable changes due to Earth’s dynamics and its movements relative to the sun and moon.
Daily Alternation
- Day and night: Influences all ecosystems except those without sunlight. During the day, photosynthesis dominates in marine ecosystems; respiration dominates at night. Photosynthetic organisms move towards the surface during the day and away at night. Terrestrial animals may be active during the day or night.
Seasonal Alternation
- Alternation of seasons: Affects all ecosystems, especially those in temperate zones, where organisms adapt to cyclical changes throughout the year.
Ecological Succession
Ecological succession is the sequence of changes in an ecosystem resulting from its internal dynamics. Succession is a slow, gradual, and progressive evolution of an ecosystem from an initial state of low biodiversity to a final state of greater diversity.
General Changes During Succession
- Increased species diversity.
- Increased structural complexity.
- Increased biomass.
- Increased energy efficiency.
- Increased productivity.
Climax Community
A climax community is a stable state of an ecosystem, marking the end of succession.
Types of Succession
- Primary succession: Occurs in areas not previously colonized, such as bare rock or newly formed land.
- Secondary succession: Occurs in areas where a previous community was partially or entirely eliminated by a disturbance.
Pest Control
Chemical Control
Pests can be controlled with chemical products called pesticides. In agriculture, insecticides control insects, herbicides eliminate weeds, and fungicides prevent mold growth.
Benefits of Pesticides
- Improved crop yields.
- Control of certain epidemics.
Drawbacks of Pesticides
- Resistance development.
- Environmental pollution.
- High persistence in the environment.
- Lack of selectivity.
- Bioaccumulation.
Biological Control
Biological control uses living organisms or specific parasites/predators to regulate pest populations, reducing them to very low densities. It is a slower method than chemical control but offers precise and careful management of population dynamics.