17.1 What is an Ecosystem?
- Ecosystem: A biological community of interacting organisms and their physical environment.
- Biotic Factors: All living things in an ecosystem, such as plants, animals, and microorganisms.
- Abiotic Factors: Non-living factors in the environment, such as temperature, light, water, and soil.
17.2 Energy Flow in Ecosystems
- Producers: Organisms, mostly plants, that make their own food through photosynthesis using sunlight, carbon dioxide, and water.
- Examples: Green plants, algae, and some bacteria.
- Consumers: Organisms that eat other organisms to obtain energy. They are classified into:
- Primary Consumers: Herbivores that eat producers (plants).
- Secondary Consumers: Carnivores that eat herbivores.
- Tertiary Consumers: Carnivores that eat other carnivores.
Food Chains: Show a linear flow of energy.
Example:
- Grass → Rabbit → Fox.
Food Webs: A complex network of food chains that shows how different species are interconnected in an ecosystem.
17.3 Nutrient Cycling
- Nutrient Cycling: The process of recycling elements like carbon, nitrogen, and phosphorus through an ecosystem, ensuring that they are reused by living organisms.
Carbon Cycle:
- Photosynthesis: Plants absorb CO₂ and produce glucose.
- Respiration: Organisms release CO₂ back into the atmosphere through respiration.
- Decomposition: Decomposers break down dead organisms, releasing carbon into the soil.
- Combustion: The burning of fossil fuels releases CO₂ into the atmosphere.
Nitrogen Cycle:
- Nitrogen Fixation: Bacteria in the soil or in the root nodules of legumes convert atmospheric nitrogen (N₂) into nitrates (NO₃⁻) that plants can use.
- Nitrification: Nitrifying bacteria convert ammonium (NH₄⁺) into nitrates.
- Denitrification: Denitrifying bacteria convert nitrates back to nitrogen gas (N₂), which is released into the atmosphere.
17.4 Adaptation to the Environment
- Adaptations: Traits that help organisms survive and reproduce in their specific environment.
- Structural Adaptations: Physical features that improve survival.
- Example: A giraffe’s long neck for reaching high branches.
- Behavioral Adaptations: Actions organisms take to survive.
- Example: Birds migrating to warmer climates during winter.
- Physiological Adaptations: Internal processes that help organisms survive.
- Example: The ability of camels to conserve water in hot deserts.
- Structural Adaptations: Physical features that improve survival.
17.5 Population and Community
- Population: A group of organisms of the same species living in a specific area at a given time.
- Community: All the different populations of species living and interacting in the same area.
17.6 Human Impact on Ecosystems
- Deforestation: The large-scale removal of forests for agriculture, urban development, or logging. This leads to loss of biodiversity, increased CO₂ levels, and disruption of local ecosystems.
- Pollution: The contamination of air, water, and soil with harmful substances.
- Air Pollution: Caused by emissions from vehicles and industries.
- Water Pollution: Chemicals, sewage, and waste products polluting water bodies.
- Soil Pollution: Pesticides, fertilizers, and industrial waste harming soil.
- Climate Change: The result of human activities, especially burning fossil fuels, increasing greenhouse gas emissions, leading to global warming and severe weather events.
- Overfishing: Catching fish at a rate faster than they can reproduce, leading to depletion of fish populations and disrupting marine ecosystems.
17.7 Conservation
- Conservation: The protection and management of biodiversity to ensure that natural resources are used sustainably.
- In-situ Conservation: Protecting species in their natural habitats.
- Example: National parks and wildlife reserves.
- Ex-situ Conservation: Protecting species outside their natural habitats.
- Example: Zoos, botanical gardens, and seed banks.
- Sustainable Resource Management: Managing resources (like water, forests, fisheries) so they can regenerate and support future generations.
- In-situ Conservation: Protecting species in their natural habitats.
17.8 Ecological Pyramids
- Pyramid of Numbers: Shows the number of organisms at each trophic level in a food chain.
- Typically, the number of producers is higher than consumers.
- Pyramid of Biomass: Shows the total dry mass of organisms at each trophic level.
- Decreases as you move up the pyramid.
- Pyramid of Energy: Shows the flow of energy through an ecosystem, with the most energy available at the producer level.