Ecology is the study of how living organisms interact with their environment. An ecosystem is a functional unit consisting of living organisms and non-living components that interact with each other. Its nature is shaped by geographical features (e.g., hills, rivers, lakes) and climatic conditions (e.g., sunlight, temperature, rainfall). This unit will explore ecosystems, community ecology, and various ecological concepts and processes.
Learning Outcomes
Understand the components and structure of ecosystems.
Explore the roles of organisms in ecological niches and habitats.
Examine ecological interactions like food webs, food chains, and biogeochemical cycles.
Analyze factors affecting ecosystem productivity and balance.
Community Ecology
Community Ecology investigates interactions between species and their environment, affecting community structure, diversity, and abundance patterns.
Population: Consists of organisms of one species in an area, interacting and interbreeding.
Organism: The smallest ecological unit; it can be a prokaryote (cells without nuclei) or a eukaryote (cells with nuclei).
The living components, classified based on their functions:
Producers (Autotrophs): Organisms that make energy resources (e.g., plants via photosynthesis).
Consumers (Heterotrophs): Organisms that gain energy by consuming organic material.
Omnivores: Organisms that consume both producers and other consumers.
Detritivores/Decomposers/Scavengers: Organisms that feed on dead organic matter and waste.
Important Note
Biomass: The total organic material produced by plants. Primary Productivity: The rate at which producers create biomass through photosynthesis or chemosynthesis.
Ecosystem Structures
An ecosystem’s self-sustaining nature includes various structural factors:
Species Composition: Varies with geography, topography, and climate.
Stratification: Vertical layering of vegetation in dense areas.
Trophic Structure: The specific food chains and food webs of each ecosystem.
Standing State: Inorganic nutrient levels present in the soil/water.
Standing Crop: The total living biomass in an ecosystem.
Ecological Niches and Habitat
Ecological Niche: The role a species plays within its community, describing its response to resource distribution, competition, and how it alters its surroundings.
Habitat: The physical environment where an organism lives. Species may share habitats but occupy different niches to coexist.
Ecosystem Functions
Ecosystems perform several key functions:
Nutrient Cycling: Circulation of materials like carbon, nitrogen, and water.
Biological Regulation: Regulation of organisms by the environment and vice versa.
Food Webs and Food Chains
Food Web: A network of interconnected food chains, describing who eats whom.
Food Chain: The transfer of matter and energy between organisms in an ecosystem, detailing the trophic interactions.
Important Note: Changes in population size in a food chain affect other populations, maintaining balance within the community.
Ecological Pyramids
Pyramid of Biomass: Represents the energy amount in the biomass of each trophic level.
Pyramid of Number: Displays the number of organisms at each trophic level.
Pyramid of Energy: Explains energy flow between trophic levels (10% Rule).
Pyramid Type
Measurement
Shape
Biomass
Grams/m²
Upright/Inverted
Number
Organisms count
Varies
Energy
Energy flow
Always Upright
Ecosystem Productivity
Ecosystem Productivity measures organic matter accumulation over time:
Gross Primary Productivity (GPP): Total biomass production by producers.
Net Primary Productivity (NPP): Biomass available to consumers after producer respiration.
Secondary Productivity (SP): Biomass produced by consumers.
Net Productivity (NP): Overall biomass accumulation in an ecosystem.
Energy Flow in the Ecosystem
Energy flows through ecosystems in a cyclic manner, primarily through food chains and food webs. Major interrelated mechanisms include:
Water Cycle: Continuous movement of water through evaporation, condensation, precipitation, and infiltration.
Carbon Cycle: Involves photosynthesis and respiration, maintaining carbon balance in the atmosphere.
Oxygen Cycle: Linked to the carbon cycle, involving plant photosynthesis and animal respiration.
Nitrogen Cycle: Recycling of nitrogen through plants, animals, soil, and nitrogen-fixing bacteria.
Phosphorus Cycle: Movement of phosphorus through soil, water, and living organisms.
Important Note
Disruption of these natural cycles due to human activities may lead to ecosystem degradation.
Ecosystem Patterns
Three recognized ecosystem patterns include:
Zonation: Horizontal species distribution gradient.
Stratification: Vertical distribution based on organism height.
Succession: Temporal change in species distribution, leading to a mature climax community.
Destruction and Tolerance in Ecosystems
Human activities threaten ecosystem balance, affecting biodiversity. Tolerance Range defines the optimal abiotic conditions for populations, influenced by factors such as light, temperature, water, and soil quality.
Terms to Know
Term
Definition
Ecological Succession
Changes in ecosystems over time due to seasonal or prolonged shifts.
Bio Capacity
The capacity of an area to provide resources and absorb wastes.
Bio Indicators
Biological processes or species used to assess environmental changes.
Types of Ecosystems
Terrestrial Ecosystems
Forest: Largest, complex ecosystems, serve as habitats and carbon sinks.
Grassland: Areas with low rainfall; divided into tropical and temperate grasslands.
Desert: Arid areas with extreme climatic conditions.
Agro-Ecosystem: Man-made ecosystems, contributing to soil fertility through symbiotic relationships.
Aquatic Ecosystems
Pond: Simple ecosystems with dry and wet phases.
Lake: Permanent form of pond ecosystems with diverse algae and plankton populations.
River: Dynamic freshwater ecosystems, supporting various fish species.
Marine: Largest ecosystem type; sunlight penetration affects organism distribution.
Factors Affecting Ecosystem
Climatic Factors: Sunlight, temperature, water availability, and wind.
Topographical Factors: Altitude influences temperature and biotic associations.
Biotic Factors: Interactions like mutualism, competition, and predation shape ecosystems.
Comparison of Climatic, Edaphic, and Biotic Factors
Factor Type
Description
Climatic
Sunlight, temperature, water availability, wind
Edaphic
Soil quality, affecting vegetation
Biotic
Interactions between organisms (mutualism, predation)
Important Note: Climatic changes can alter ecosystem dynamics and organism survivability.
Integration of Cycles and Human Impact
Biogeochemical cycles are crucial for life, interlinked across ecosystems. Human interference can degrade these cycles, risking ecosystem collapse and endangering human survival.
Ecosystem Destruction and Tolerance Range
Ecosystems like wetlands, mangroves, and coral reefs maintain delicate balances, disrupted by human activities. Tolerance Range describes the range of abiotic factors conducive to population survival, beyond which organisms decline.
One Multiple Choice Question
Which of the following is a primary function of an ecosystem?