Ecology: Principles and Concepts

Ecology Definition

• Ecology stems from the Greek words "oikos" (household) and "logos" (study), literally meaning the study of household.
• It studies "life at home," highlighting the relationships between organisms and their environment.
• More scientifically, ecology is the study of the environmental house, encompassing all its organisms and functional processes.

Basic Principles and Concepts of Ecology

• Levels of organization arrange hierarchically from ecosphere to cells, showing emergent properties at each level.
• Hierarchy is a graded arrangement, while a system comprises regularly interacting, interdependent components forming a unified whole.
• A biosystem includes living (biotic) and nonliving (abiotic) components, ranging from genetic to ecological systems.
• Ecology primarily focuses on system levels beyond individual organisms.

Ecological Levels

• Population: A group of individuals of the same species in a common geographical area.
• Community: Two or more populations of different species occupying the same area; populations and communities include only biotic factors.
• Ecosystem: A community plus its abiotic factors (e.g., soil, rain, temperature, nutrients), where the community and non-living environment function together.
• Landscape: A heterogenous area composed of interacting ecosystems repeated similarly throughout.
• Biome: A large regional or subcontinental system characterized by a major vegetation type or identifying landscape aspect.
• Ecosphere: The largest, nearly self-sufficient biological system including all Earth's living organisms interacting with the physical environment as a whole in a self-adjusting state.

Natural Ecosystem Attributes

• Biotic (living) organisms and abiotic (nonliving) environment are inseparably interrelated, comprising any unit that includes a biotic community in a given area interacting with the physical environment.
• A flow of energy leads to defined biotic structures and cycling of materials between living and nonliving components; it is also the first in the ecological hierarchy that is complete with all the components important for survival.
• Ecosystems are open systems with constant entering and leaving processes; the main source of energy for the ecosphere is the sun, but other sources may be important for numerous ecosystems.
• Energy flows out of the system as heat and in transformed forms, such as organic matter (food and waste products) and pollutants.
• Materials, including nutrients necessary for life, can be reused, and the community of autotrophs and heterotrophs are linked together with appropriate energy flows, nutrient cycles, and storages.

Trophic Structure of the Ecosystem

• Ecosystems divide into autotrophic stratum (upper) or "green belt" of chlorophyll-containing plants, which fix light energy and use simple organic substances; and heterotrophic stratum (lower) or "brown belt" of soils and sediments, decaying matter, roots, etc., which utilizes, rearranges, and decomposes complex materials.

Components of an Ecosystem

• Organic substances: involved in material cycles (e.g., C, N, CO2, H2O).
• Organic compounds: link biotic and abiotic components (e.g., protein, carbohydrates, lipids, humic substances).
• Air, water, and substrate environment: includes climate regime and other physical factors.
• Producers (autotrophic organisms): mostly green plants that manufacture food from simple inorganic substances.
• Phagotrophs: heterotrophic organisms (animals) that ingest other organisms or particulate organic matter.
• Saprotrophs: decomposers (mainly bacteria and fungi) that obtain energy by breaking down dead tissues or absorbing dissolved organic matter (DOM) from plants and animals.

Energy Concepts

• The first law of thermodynamics: Energy may be transformed from one form to another, but is neither created nor destroyed.
• The second law of thermodynamics: No process involving energy transformation will spontaneously occur unless energy degrades from a concentrated form into a dispersed form.
• Food from plant photosynthesis represents potential energy, used by organisms.
• Energy partitioning in food chains and food webs involves energy transfer from autotrophs through a series of organisms that consume and are consumed.
• The food chain exists in two basic types: the grazing food chain and detritus food chain.

Biogeochemical Cycles

• The chemical elements circulate in pathways from environment to organisms and back, including Cycling of Nitrogen, Cycling of Phosphorus, Cycling of Sulfur, and Cycling of Carbon.

Factors that Contribute to an Organism's Ecological Niche

• The niche encompasses environmental factors that influence a species' growth, survival, and reproduction.
• The limiting factor principle says that too much or too little of any abiotic factor can limit or prevent population growth, even if others are near the optimal range of tolerance.
• Important limiting abiotic factors in aquatic life zones include temperature, sunlight, nutrient availability, and salinity

Types of Interactions Between Two Species

• Neutralism, Competition, Resource Use Type, Amensalism, Commensalism, Parasitism, Predation, Protocooperation, and Mutualism.