Earth's Biosphere: Ecosystems, Biomes, and Biodiversity

Earth's Biosphere and Ecosystems

The biosphere of the Earth is established by living organisms within a thin layer where energy comes from the sun. An ecosystem is formed by a community of living organisms that occupy a given space, the relationships established between them, and the physical environment.

Key Ecological Concepts

• Ecotone: Areas that limit ecosystems.
• Habitat: The area that presents the physicochemical conditions required for a population to properly function.

Components of an Ecosystem

Landforms are part of the ecosystem, which is part of the ecosphere. The components include:

• Biocenosis: The community of living organisms.
• Biotopo: The physical environment.

Biotopo Components

These include:

• Characteristics of the substrate: The support on which the ecosystem is located (aquatic and terrestrial).
• Climatic characteristics.
• Hydrological characteristics: Quantity and quality of water.

Energy Flow in Ecosystems

Ecosystems consist of:

• Autotrophic organisms: Energy flows through photoautotrophs and chemoautotrophs.
• Heterotrophic organisms: Consumers (primary, secondary, tertiary), scavengers, saprophytes, and decomposers.

Biomass and Production

• Biomass: The amount of energy in living organisms (g · C/m2).
• Necromass: Constituent matter (remains).
• Production: The quantity of increased biomass of a trophic level over a certain time.
• Primary Production (PP): The amount of material fixed by producers from solar radiation and inorganic matter.
• Secondary Production (PS): Production at rest levels.
• Gross Production: Total amount of material incorporated by one trophic level in a certain time.
• Net Production: Material that is stored for growth and reproduction.

Productivity and Renewal

• Productivity: The relationship between biomass and net production, also called a standard renewal rate (prod = P / B × 100).
• Time of Renewal: The time it takes for individuals in an ecosystem to renew all their organic matter (temp.renov = B / P).
• Eco-efficiency: Measuring performance in the transmission of energy from one trophic level to the next.

Limiting Factors

• Moisture: Water loss through perspiration; relative humidity; C4 plants.
• Temperature: Affects photosynthesis.
• Nutrients: Materials for photosynthesis, nitrogen, and phosphorus.
• Light: Affects photosynthesis, especially in deep marine ecosystems.
• Ecological Valence: Tolerance range of an environmental parameter that acts as a constraint.

Trophic Relationships

Consumer-resource interactions that define the living creatures that inhabit an ecosystem, allowing the transfer of energy.

• Food Chain: Linear route of energy transfer from producers to consumers in successive trophic levels.
• Food Web: A set of interconnected food chains. Conclusions from studies are grouped into trophic levels. Different species can serve as food or feed on species framed within the web. Removal of one or more populations alters the balance. Diversity indicates a good state of preservation and evolution.

Trophic Pyramids

Describes the distribution of matter or energy between different trophic levels of the ecosystem (biomass pyramid or not).

The 10% Rule

Only 10% of energy from one trophic level is passed to the next and can be used by the individuals that make it up.

Interspecific Relations

These include predation, parasitism, mutualism, symbiosis (benefits up to a point where one cannot live without the other), and competition.

Ecological Niche

The set of conditions, both biotic and abiotic, under which a species can develop, establishing relationships with the environment and the adaptations it has to function (potential needs; made-real).

Climax Ecosystem

An ecosystem whose community is stable over time with respect to environmental conditions and cannot increase its biomass.

Ecological Succession

Changes experienced by an ecosystem as a consequence of its own internal dynamics, leading to a state of maximum stability and equilibrium.

Biodiversity

The variety of organisms in a given region.

• Levels of study: genetic, specific, ecosystemic.

Biodiversity Measures

• Alpha: Species richness measured in an ecosystem.
• Beta: Measures differences in diversity.
• Delta: Similarity in diversity among communities in similar habitats.
• Gamma: Regional diversity scale.

Biomes

An area defined geographically by climatic and ecological conditions that allow the development of specific communities of plants, animals, and microorganisms characteristic of that space.

Terrestrial Biomes

These include:

• Frozen desert
• Tundra: Dark much of the year (-15 to 5°C, 300mm precipitation, permafrost).
• Taiga: (-40°C, 250-500mm precipitation, light shortage).
• Temperate deciduous forest: (750-1500mm precipitation).
• Sclerophyll forest
• Steppe/Prairie: (20-29°C).
• Desert
• Savannah
• Rainforest