IB ESS Ecosystem Study Guide PDF

**IB ESS Unit 2: The Ecosystem - Study Guide** **Key Concepts** 1. **Ecosystems** - Definition: An ecosystem is a community of living organisms interacting with their physical environment, involving the flow of energy and cycling of nutrients. - Components:...

**IB ESS Unit 2: The Ecosystem - Study Guide** **Key Concepts** 1. **Ecosystems** - Definition: An ecosystem is a community of living organisms interacting with their physical environment, involving the flow of energy and cycling of nutrients. - Components: - *Biotic*: All living components (plants, animals, microorganisms). - *Abiotic*: Non-living components (light, temperature, water, soil, etc.). 2. **Energy Flow in Ecosystems** - *Producers (Autotrophs)*: Organisms that produce their own food (e.g., plants, algae). - *Consumers (Heterotrophs)*: Organisms that rely on other organisms for food. Types include herbivores, carnivores, omnivores, and decomposers. - *Decomposers*: Organisms that break down dead organic material (e.g., bacteria, fungi). - *Food Chain and Food Web*: - Food chain: A linear sequence showing the flow of energy. - Food web: A complex network of interconnected food chains. - *Trophic Levels*: The different levels in a food chain/web (primary producer, primary consumer, secondary consumer, etc.). - *Energy Loss*: Only about 10% of energy is passed from one trophic level to the next (due to respiration, movement, and other biological processes). 3. **Nutrient Cycling** - Nutrients (e.g., carbon, nitrogen, phosphorus) are cycled through ecosystems. - Key processes: - *Carbon Cycle*: The movement of carbon through the atmosphere, hydrosphere, biosphere, and lithosphere. - *Nitrogen Cycle*: The conversion of nitrogen between its various chemical forms, including nitrogen fixation, nitrification, denitrification, etc. - *Phosphorus Cycle*: The movement of phosphorus through the soil, water, and living organisms. 4. **Primary Productivity** - **Gross Primary Productivity (GPP)**: Total energy captured by producers. - **Net Primary Productivity (NPP)**: Energy available to the next trophic level after accounting for the energy used by producers in respiration. - Factors influencing primary productivity: sunlight, temperature, water, nutrient availability, etc. 5. **Succession** - **Primary Succession**: The process of ecosystem development on previously lifeless areas (e.g., after a volcanic eruption). - **Secondary Succession**: The recovery of ecosystems after a disturbance (e.g., forest fire, deforestation). - Stages: Pioneer species → Intermediate species → Climax community. 6. **Human Impact on Ecosystems** - Habitat destruction, pollution, invasive species, climate change, and overexploitation affect ecosystem balance. - Conservation efforts focus on protecting biodiversity and restoring ecosystems. **IB ESS Exam-Like Questions** **Question 1: Energy Flow in Ecosystems** **a)** Define the term \"trophic level\".\ **b)** Explain the concept of energy loss between trophic levels using an example of a terrestrial food chain.\ **c)** Why is the transfer of energy between trophic levels not 100% efficient? **Answer**\ **a)** A trophic level is a step in the food chain or food web, representing an organism\'s position in the sequence of energy flow through an ecosystem. Each trophic level corresponds to a specific role in the ecosystem (producers, primary consumers, secondary consumers, etc.). **b)** In a terrestrial food chain: - *Producers (e.g., grass)* are eaten by primary consumers (e.g., rabbits). - *Primary consumers* are eaten by secondary consumers (e.g., foxes). - *Secondary consumers* are eaten by tertiary consumers (e.g., eagles).\ Energy is transferred from one trophic level to the next, but not all of the energy is passed on. A significant amount is lost as heat during respiration, movement, and metabolic processes. For example, if the grass has 1000 J of energy, only about 100 J might be transferred to the rabbit, and about 10 J might be passed to the fox. **c)** The transfer of energy between trophic levels is not 100% efficient because much of the energy is lost as heat through metabolic processes (respiration, movement, digestion) and some is not consumed or assimilated by the next trophic level (e.g., parts of organisms may not be eaten). **Question 2: Nutrient Cycling** **a)** Describe the main steps of the nitrogen cycle.\ **b)** Explain how human activities can disrupt the nitrogen cycle. **Answer**\ **a)** The nitrogen cycle involves the following key steps: - *Nitrogen Fixation*: Atmospheric nitrogen (N₂) is converted into ammonia (NH₃) or nitrates (NO₃⁻) by nitrogen-fixing bacteria in soil or by lightning. - *Nitrification*: Ammonia is converted into nitrites (NO₂⁻) and then into nitrates (NO₃⁻) by nitrifying bacteria. - *Assimilation*: Plants absorb nitrates and incorporate them into amino acids and proteins. - *Ammonification*: Decomposers break down organic nitrogen compounds in dead organisms and waste, releasing ammonia into the soil. - *Denitrification*: Denitrifying bacteria convert nitrates back into atmospheric nitrogen (N₂), completing the cycle. **b)** Human activities that disrupt the nitrogen cycle include: - *Use of synthetic fertilizers*: These increase the amount of nitrogen in the soil, which can lead to nutrient pollution in water bodies (eutrophication). - *Burning of fossil fuels*: This releases nitrogen oxides (NOₓ), contributing to air pollution and acid rain. - *Deforestation and land-use changes*: These can reduce the amount of nitrogen-fixing vegetation, disrupting the cycle. **Question 3: Primary Productivity** **a)** What is Net Primary Productivity (NPP), and why is it an important concept in ecosystems?\ **b)** Identify two factors that influence primary productivity in terrestrial ecosystems and explain their effects. **Answer**\ **a)** Net Primary Productivity (NPP) is the rate at which energy is stored as biomass in producers (plants) after accounting for the energy they use in respiration. NPP is crucial because it represents the amount of energy available for consumption by primary consumers (herbivores) and higher trophic levels, indicating the overall productivity and health of an ecosystem. **b)** Two factors that influence primary productivity in terrestrial ecosystems: - *Sunlight*: The availability of sunlight influences the rate of photosynthesis in plants. More sunlight typically increases productivity, especially in regions near the equator. - *Water availability*: Water is necessary for photosynthesis. In regions with high rainfall (e.g., tropical rainforests), productivity is higher compared to arid regions, where water scarcity limits plant growth. **Question 4: Succession** **a)** Differentiate between primary and secondary succession.\ **b)** Describe one human-induced disturbance that could lead to secondary succession. **Answer**\ **a)** - *Primary Succession*: Occurs in an area where no previous community existed, such as after a volcanic eruption or the formation of a new island. It begins with pioneer species (e.g., lichens, mosses) that gradually build soil, allowing more complex plant and animal communities to develop. - *Secondary Succession*: Occurs in an area where a disturbance (e.g., fire, farming, logging) has disrupted an existing community but left the soil intact. It is faster than primary succession because the soil already contains seeds and nutrients. **b)** An example of a human-induced disturbance leading to secondary succession is deforestation. When forests are cleared for agriculture or urban development, the soil and seed bank remain, allowing for the re-establishment of plant and animal communities over time. **Question 5: Human Impact on Ecosystems** **a)** How can the introduction of invasive species impact local ecosystems?\ **b)** Describe one method of conserving biodiversity in ecosystems. **Answer**\ **a)** Invasive species can disrupt local ecosystems by outcompeting native species for resources (food, habitat), introducing diseases, or altering the physical environment (e.g., through predation or grazing). This can lead to a decline in biodiversity, as native species may not be adapted to cope with the new competitors or predators. **b)** One method of conserving biodiversity is *establishing protected areas*, such as national parks or nature reserves. These areas limit human activity, provide safe habitats for endangered species, and help maintain ecosystem functions and services. 1. **Ecosystem**: A community of organisms interacting with each other and their physical environment. 2. **Biotic**: The living components of an ecosystem (e.g., plants, animals, microorganisms). 3. **Abiotic**: The non-living components of an ecosystem (e.g., temperature, sunlight, soil, water). 4. **Biodiversity**: The variety of life forms within a given ecosystem or on Earth as a whole, including genetic, species, and ecosystem diversity. 5. **Population**: A group of individuals of the same species living in the same area. 6. **Community**: A group of interacting species living in the same area. 7. **Habitat**: The natural environment in which an organism lives. 8. **Niche**: The role and position a species has in its environment, including how it gets its energy and nutrients. **Energy Flow and Trophic Levels** 9. **Trophic Level**: A level in a food chain or food web, representing an organism\'s position in the flow of energy. 10. **Producers (Autotrophs)**: Organisms that produce their own food, typically through photosynthesis (e.g., plants, algae). 11. **Consumers (Heterotrophs)**: Organisms that consume other organisms for food. They are classified into primary, secondary, and tertiary consumers. 12. **Decomposers**: Organisms that break down dead organic matter, recycling nutrients back into the ecosystem (e.g., bacteria, fungi). 13. **Food Chain**: A linear sequence showing the flow of energy from producers to primary, secondary, and tertiary consumers. 14. **Food Web**: A complex network of interconnected food chains in an ecosystem. 15. **Energy Pyramid**: A graphical representation of the flow of energy through trophic levels, showing energy loss as it moves up the food chain. **Nutrient Cycling** 16. **Nutrient Cycle**: The circulation of essential elements (e.g., carbon, nitrogen, phosphorus) through the ecosystem. 17. **Carbon Cycle**: The process by which carbon is exchanged between living organisms, the atmosphere, the oceans, and the Earth's crust. 18. **Nitrogen Cycle**: The movement and transformation of nitrogen through different forms, including nitrogen fixation, nitrification, assimilation, and denitrification. 19. **Phosphorus Cycle**: The movement of phosphorus through the soil, water, and living organisms. 20. **Fixation**: The process of converting nitrogen gas (N₂) into forms that plants can use, such as ammonia (NH₃). 21. **Nitrification**: The conversion of ammonia (NH₃) into nitrates (NO₃⁻) by bacteria in the soil. 22. **Denitrification**: The conversion of nitrates (NO₃⁻) back into nitrogen gas (N₂) by bacteria, completing the nitrogen cycle. **Succession and Ecosystem Change** 23. **Primary Succession**: The establishment of an ecosystem in an area that has not previously supported life (e.g., after a volcanic eruption). 24. **Secondary Succession**: The recovery of an ecosystem following a disturbance that does not destroy the soil (e.g., after a forest fire or agricultural abandonment). 25. **Pioneer Species**: The first species to colonize a barren or disturbed environment, initiating ecological succession. 26. **Climax Community**: A stable, mature community that results from ecological succession, typically characterized by a diversity of species. 27. **Invasive Species**: Non-native species that spread rapidly and have negative impacts on local ecosystems and biodiversity. **Human Impact on Ecosystems** 28. **Sustainability**: The ability of an ecosystem or human practice to maintain ecological processes, functions, and productivity over the long term. 29. **Ecological Footprint**: A measure of the impact of human activities on the environment, including the area of land and resources needed to sustain a population. 30. **Pollution**: The introduction of harmful substances or contaminants into the environment that cause damage to ecosystems. 31. **Eutrophication**: The process by which excessive nutrients (often nitrogen and phosphorus) lead to algae blooms, oxygen depletion, and loss of biodiversity in aquatic ecosystems. 32. **Deforestation**: The large-scale removal of forests, typically for agriculture or urban development, leading to habitat loss and changes in carbon and water cycles. 33. **Habitat Destruction**: The process by which natural habitats are altered or destroyed, often due to human activity, leading to species loss. 34. **Overexploitation**: The unsustainable use of natural resources, such as overfishing, leading to depletion of the resource. **Conservation and Management** 35. **Conservation**: The protection, preservation, management, and restoration of ecosystems and biodiversity. 36. **Biodiversity Hotspot**: A region that is both rich in endemic species and has experienced significant habitat loss, requiring conservation attention. 37. **Protected Areas**: Areas designated for conservation purposes, such as national parks or nature reserves, to safeguard ecosystems and species. 38. **Restoration Ecology**: The science of restoring damaged ecosystems to a more natural or functional state. 39. **Endangered Species**: Species at risk of extinction due to habitat loss, overhunting, pollution, or other factors. 40. **Gene Pool**: The total genetic diversity found within a population or species. **Environmental Economics and Policy** 41. **Environmental Impact Assessment (EIA)**: A process used to evaluate the potential environmental effects of a proposed project before it is carried out. 42. **Carrying Capacity**: The maximum population size that an ecosystem can support without degradation. 43. **Sustainable Development**: Development that meets the needs of the present without compromising the ability of future generations to meet their own needs. 44. **Cap and Trade**: A market-based approach to reducing pollution by setting a cap on emissions and allowing companies to buy and sell permits to pollute. 45. **Recycling**: The process of converting waste materials into new products, reducing the consumption of raw resources. **Important Mathematical and Scientific Terms** 46. **Biomass**: The total mass of living organisms in a given area or ecosystem. 47. **Photosynthesis**: The process by which plants convert sunlight, carbon dioxide, and water into glucose and oxygen. 48. **Respiration**: The process by which cells break down glucose to release energy, producing carbon dioxide and water as byproducts. 49. **Biotic Potential**: The maximum reproductive capacity of an organism under ideal environmental conditions. 50. **Carrying Capacity**: The largest population of a species that an environment can support sustainably.