Ecology-Ecosystems Ecology And Environment Topic
Ecosystems and Energy Flow:
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Definition of an ecosystem and its components:
- An ecosystem is a self-sustaining community of living organisms (biotic components) interacting with their non-living environment (abiotic components) within a defined ecological boundary.
- NCERT: Class 11, Biology, Chapter 14: Ecosystem.
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Energy flow in ecosystems:
- Producers: Autotrophic organisms that convert inorganic substances (CO2, H2O, minerals) into organic compounds using sunlight through photosynthesis.
- Consumers: Heterotrophic organisms that obtain their organic compounds from other organisms. They are classified into primary consumers (herbivores), secondary consumers (carnivores), tertiary consumers (top predators), etc.
- Decomposers: Organisms that break down dead organic matter into simpler inorganic substances.
- Trophic levels: Different stages of energy transfer through a food chain or web.
- Food chain: A linear sequence of organisms through which energy and nutrients pass, starting with producers and ending with top predators.
- Food webs: Interconnected network of food chains, representing the complex energy flow within an ecosystem.
- Energy pyramids: Graphical representations illustrating the loss of energy at each trophic level in an ecosystem.
- NCERT: Class 11, Biology, Chapter 14: Ecosystem.
Biogeochemical Cycles:
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Carbon cycle:
- Processes involved: Photosynthesis, respiration, decomposition, combustion, ocean absorption.
- Reservoirs: Atmosphere, oceans, terrestrial ecosystems, fossil fuels.
- Human impacts: Burning fossil fuels, deforestation, changes in land use, leading to increased atmospheric CO2 levels and carbon emissions.
- NCERT: Class 11, Biology, Chapter 14: Ecosystem.
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Nitrogen cycle:
- Processes involved: Nitrogen fixation, nitrification, assimilation, ammonification, denitrification.
- Reservoirs: Atmosphere, soil, living organisms, nitrogen-fixing bacteria.
- Human impacts: Excessive use of fertilizers, leading to eutrophication and water pollution; nitrogen-based air pollution.
- NCERT: Class 11, Biology, Chapter 13: Organisms and Populations.
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Phosphorus cycle:
- Processes involved: Weathering of rocks, uptake by plants, decomposition, mineralization, immobilization.
- Reservoirs: Continental rocks, oceans, sediments, living organisms.
- Human impacts: Extensive use of phosphorus fertilizers, leading to eutrophication of water bodies; mining activities.
- NCERT: Class 12, Biology, Chapter 15: Biodiversity and Conservation.
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Sulfur cycle:
- Processes involved: Decomposition, sulfur oxidation, sulfate reduction, biological assimilation, volcanic release.
- Reservoirs: Atmosphere, oceans, terrestrial ecosystems, elemental sulfur.
- Human impacts: Burning fossil fuels, industrial activities, and volcanic eruptions.
- NCERT: Class 12, Biology, Chapter 15: Biodiversity and Conservation.
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Water cycle:
- Components: Evaporation, condensation, precipitation, infiltration, runoff, transpiration.
- Processes: Continuous movement of water between the Earth and the atmosphere.
- Importance: Crucial for maintaining the Earth’s climate, distributing freshwater resources, supporting ecosystems.
- NCERT: Class 12, Biology, Chapter 14: Ecosystem.
Community Ecology:
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Species diversity:
- Importance: Measure of the variety and relative abundance of species in a community.
- Measurement: Shannon Index (H’= -Σpi * ln pi): Considers both species richness (number of species) and evenness (uniformity in species distribution). Simpson Index (D = Σ (n/N)^2): Gives more weight to species abundance and assesses community dominance.
- Factors affecting species diversity: Habitat complexity, climate, geographic location, resource availability, interspecific interactions.
- NCERT: Class 12, Biology, Chapter 15: Biodiversity and Conservation.
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Ecological niche:
- Concept: Functional role and position of a species within an ecosystem, including resource utilization and interactions.
- Types of niches: Fundamental niche (potential niche), realized niche (actual niche due to interactions).
- NCERT: Class 11, Biology, Chapter 13: Organisms and Populations.
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Ecological succession:
- Primary succession: Succession occurring on bare or newly formed surfaces where no living community exists. Pioneers species, such as lichens and mosses, initiate the process.
- Secondary succession: Succession that follows the disruption or destruction of an existing community. It occurs more rapidly and involves the reestablishment of species.
- Climax community: Stable, self-sustaining community that represents the final stage of ecological succession.
- NCERT: Class 12, Biology, Chapter 15: Biodiversity and Conservation.
Population Ecology:
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Population characteristics:
- Population density: Number of individuals per unit area or volume.
- Natality (birth rate): Number of new individuals added to the population per unit time.
- Mortality (death rate): Number of individuals removed from the population per unit time.
- Age structure: Distribution of individuals in a population based on age groups.
- Dispersion patterns: Spatial distribution of individuals within a habitat.
- NCERT: Class 12, Biology Chapter 13: Organisms and Populations.
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Population growth models:
- Exponential growth model: Population grows at a constant percentage rate over time. Assumes unlimited resources and no limiting factors. dN/dt = rN (N = population size, r = intrinsic growth rate, t = time)
- Logistic growth model: Population growth slows down as it reaches the carrying capacity of the environment. dN/dt = rN * (K-N)/K (K = carrying capacity)
- NCERT: Class 12, Biology Chapter 13: Organisms and Populations.
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Carrying capacity and limiting factors:
- Carrying capacity: Maximum population size that can be sustained indefinitely by a given environment without degradation.
- Limiting factors: Environmental factors (biotic or abiotic) that restrict the growth or survival of a population.
- NCERT: Class 12, Biology Chapter 13: Organisms and Populations.
Conservation of Ecosystems and Biodiversity:
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Importance of biodiversity:
- Ecological significance: Maintains ecosystem stability, provides essential ecological services (pollination, nutrient cycling, climate regulation), and forms the genetic pool for future evolution.
- Economic importance: Provides resources for medicine, agriculture, biotechnology, and tourism.
- Cultural and aesthetic value: Inspires art, literature, and spiritual practices.
- NCERT: Class 12, Biology, Chapter 15: Biodiversity and Conservation.
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Threats to biodiversity:
- Habitat destruction: Deforestation, urbanization, agriculture expansion, mining.
- Hunting and overexploitation: Overharvesting of species for food, fur, or medicinal purposes.
- Pollution: Water pollution, air pollution, land pollution.
- Invasive species: Non-native species introduced into new environments and outcompete native species.
- Climate change: Shifts in climatic conditions affect species distribution and survival.
- NCERT: Class 12, Biology, Chapter 15: Biodiversity and Conservation.
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Conservation strategies:
- Protected areas: Designating areas of land and water for biodiversity protection (national parks, wildlife sanctuaries, biosphere reserves).
- Sustainable resource management: Balancing resource utilization with regeneration to ensure long-term availability.
- Species reintroduction: Translocation of species to restore them to their natural habitat or establish new populations.
- Ex situ conservation: Preservation of species outside their natural habitats, such as botanical gardens, gene banks, and zoos.
- NCERT: Class 12, Biology, Chapter 15: Biodiversity and Conservation.
Environmental Issues and Sustainable Development:
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Environmental pollution:
- Air pollution: Release of harmful substances (particulates, gases, aerosols) into the atmosphere, leading to respiratory issues, acid rain, global warming.
- Water pollution: Contamination of water sources with pollutants (industrial discharge, agricultural runoff, sewage), causing eutrophication and health risks.
- Land pollution: Accumulation of toxic substances in soil, affecting soil quality, plant growth, and human health.
- Noise pollution: Excessive and undesired sounds, particularly in urban areas, causing sleep disturbance, hearing loss, and stress.
- NCERT: Class 12, Biology, Chapter 15: Biodiversity and Conservation.
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Climate change:
- Greenhouse gases (GHGs): Gases like CO2, CH4, N2O that trap heat in the Earth’s atmosphere.
- Global warming: Long-term increase in Earth’s average surface temperature due to the accumulation of GHGs.
- Human activities contributing to climate change: Burning fossil fuels, deforestation, agriculture practices.
- Impacts of climate change on ecosystems: Altered habitats, species distributions, disruptions in ecological processes, extreme weather events, melting of glaciers.
- NCERT: Class 12, Biology Chapter 15: Biodiversity and Conservation.
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Sustainable development:
- Concept: Balancing economic progress, social well-being, and environmental protection for the present and future generations.
- Principles: Equity, precaution, participation, and long-term orientation.
- Challenges: Balancing resource use, population growth, poverty reduction