Ecosystems (energy and stability).pdf

Transfers of energy and matter 1. Explain the concept of ecosystems as open systems An open system allows both energy and matter to be exchanged with its surroundings. Ecosystems, such as tropical rainforests and grasslands, are examples of open systems due to the conti...

Transfers of energy and matter 1. Explain the concept of ecosystems as open systems An open system allows both energy and matter to be exchanged with its surroundings. Ecosystems, such as tropical rainforests and grasslands, are examples of open systems due to the continuous inputs and outputs of energy and matter. 2. Describe the role of sunlight in ecosystems Sunlight serves as the primary source of energy that sustains most ecosystems on Earth. Through the process of photosynthesis, green plants and other photosynthetic organisms convert sunlight into chemical energy, which can be further utilised by other living organisms to survive. That's why plants are called the producers because they convert energy into a usable form for other organisms to live. Exception: In these sunlight-limited environments, chemosynthetic organisms play a significant role. These specialised bacteria extract energy from inorganic compounds like minerals and sulphur, instead of relying on sunlight. Through the process of chemosynthesis, these bacteria convert inorganic molecules into organic compounds. 3. Outline the flow of energy through food chains and food webs Herbivores consume plants, extracting energy from the stored organic compounds. Carnivores, in turn, feed on herbivores, continuing the transfer of energy up the food chain. This energy flow from one organism to another forms the foundation of food chains. 4. Describe the role of decomposers in nutrient cycling Decomposers play a crucial role in ecosystem processes by breaking down dead organisms and organic matter. Extract energy and nutrients from decaying materials such as leaf litter, wood, animal carcasses, and even animal faeces. Without decomposers, the world would be filled with a massive accumulation of dead plant material, deceased animals, and animal waste, likely making ecosystems unsustainable. 5. Distinguish between autotrophic and heterotrophic modes of nutrition Autotrophs, also known as primary producers, are organisms capable of synthesising organic molecules from inorganic ones using an external energy source. Heterotrophs are organisms that cannot produce their own organic molecules and rely on consuming other organisms or organic matter to obtain energy and nutrients for survival. 6. Classify organisms into trophic levels based on their position in a food chain or food web  7. Construct an energy pyramid based on ecological data The term biomass refers to the total dry mass of a group of organisms in a specific area or volume. 8. Explain the factors that contribute to energy losses in food chains Incomplete consumption: Organisms often do not consume all parts of the organism they feed on, resulting in uneaten biomass. Inefficient digestion: Organisms are unable to absorb all the energy contained in the consumed food during digestion. Inefficient energy conversion and storage: Not all energy obtained from food is efficiently converted and stored in the organism’s tissues. Used in metabolic processes: Organisms use energy for their own metabolic processes, including respiration, movement, and growth. Heat dissipation: Energy dissipates as heat as a consequence of cellular respiration and other metabolic reactions, as discussed in the upcoming text. 9. Outline the causes and consequences of heat dissipation in food chains In cell respiration, organisms use the chemical energy stored in organic compounds, such as glucose, and convert it into ATP. However, not all of the chemical energy can be fully captured and converted into ATP. As a result, some energy is inevitably lost as heat. Since living organisms cannot utilise heat as a source of energy, we say that this energy is ‘lost’ 10. Describe the factor that restricts the number of trophic levels in a food chain Energy losses between trophic levels cause a great decrease in the amount of energy stored as biomass at each successive trophic level. As energy moves up the food chain, the amount of energy available eventually becomes insufficient to sustain an additional trophic level. This limitation is what restricts the number of trophic levels present in a food chain, which typically have a maximum of four. 11. Compare and contrast primary and secondary productivity Net primary productivity refers to the rate at which organic matter is produced by autotrophs (producers) through photosynthesis, which is then available for consumption by heterotrophs (consumers). Secondary productivity refers to the rate at which consumers convert organic matter into biomass, not the generation of new organic matter by producers. 12. Explain the factors that affect primary productivity in an ecosystem Factors such as temperature, precipitation, and amount of nutrients in the soil greatly affect primary production. Regions with abundant sunlight, water, and nutrient-rich soils tend to show higher primary productivity. 13. Construct an accurate diagram of the carbon cycle 14. Explain the factors influencing an ecosystem’s capacity to function as a carbon sink or a source Whether an ecosystem is a sink or a source is dependent on the balance that exists between two essential metabolic processes: photosynthesis and cellular respiration. Photosynthesis is an essential process in the carbon cycle, as it allows autotrophs to capture carbon dioxide from the atmosphere and incorporate into organic compounds. Respiration, on the other hand, is a complementary process that releases CO2 back into the atmosphere as organisms break down organic compounds to obtain energy. Within an ecosystem, when photosynthesis rates exceed cell respiration rates, there is a net uptake of carbon dioxide from the atmosphere, making ecosystems act as carbon sinks. 15. Discuss the impact of deforestation on the carbon cycle Ecosystems with high rates of respiration relative to photosynthesis, such as decaying organic matter or actively respiring microbial communities, function as carbon sources, releasing more carbon than they absorb. The image below showcases the transition of a forest from a carbon sink to a carbon source, emphasising the impact of deforestation on the carbon cycle. 16. Describe how combustion of fossil fuels and biomass affects the carbon cycle The increased concentration of CO2 in the atmosphere from fossil fuel combustion has several effects on the carbon cycle. First, it enhances the greenhouse effect, trapping more heat and contributing to global warming and climate change. Second, it alters the equilibrium between carbon sinks and carbon sources. Natural carbon sinks, such as forests and oceans, can absorb some of the excess CO2, but they have limits to their capacity. If the rate of CO2 release exceeds the capacity of these sinks, the excess CO2 accumulates in the atmosphere, leading to higher concentration and further climate impacts. 17. Analyse and explain the short-term and long-term trends shown in the Keeling Curve Short-term: during the growing season, plants undergo photosynthesis, absorbing CO2 from the atmosphere and reducing its concentration. This leads to a decline in CO2 levels. In contrast, during the dormant season, when photosynthesis rates are lower and respiration continues, CO2 levels increase. Long-term: shows a consistent increase in CO2 levels over the years. 18. Explain the significance of photosynthesis and aerobic respiration in sustaining life on Earth Aerobic respiration is a process that relies on the presence of atmospheric oxygen produced through photosynthesis. This process produces carbon dioxide as a waste product, which is then released into the atmosphere. Carbon dioxide is in turn essential for photosynthesis to occur. This reciprocal relationship between aerobic respiration and photosynthesis forms an essential interaction between autotrophic and heterotrophic organisms. The massive fluxes of oxygen and carbon dioxide involved in these two processes continuously occur on a global scale, making them necessary for maintaining life on Earth. 19. Explain the importance of cycles of matter in the functioning of ecosystems All the chemical elements required by living organisms are recycled within ecosystems. This recycling process ensures the continual availability of essential elements for maintaining life. The recycling of all elements is essential for the sustainability of ecosystems.  Stability and change 1. Define ‘ecosystem stability’, including some examples of stable ecosystems The stability of an ecosystem is the ability to maintain its structure and function over time, despite changes or disturbances. Examples: Tropical rainforest (Amazon) 2. Outline the factors that affect stability and explain tipping points, using deforestation of the Amazon rainforest as an example Supply of energy: energy is needed for all living processes Recycling of nutrients: by the recycling of nutrients, nutrient availability can be maintained supporting the productivity of populations. Biodiversity: the more diversity the more stability because it can resist disturbances Climatic factors: the more severe weather ecosystems experience the less likely they are to be stable. Deforestation of the Amazon rainforest is a well-known example of a possible tipping point in ecosystem stability. Deforestation is the permanent removal or clearing of forests or wooded areas, usually to convert land for agricultural, industrial or urban purposes. Generally, after a small amount of tree removal, the remaining trees and vegetation in the surrounding forest can support the recovery of the cleared area. When deforestation occurs at a higher rate, it can push the forest past a critical point, where the forest's ability to regenerate and maintain its ecological functions is compromised. 3. Evaluate the use of models to investigate the effect of variables on ecosystem stability It can be helpful to investigate an ecosystem, however they tend to be quite small and represent only a small batch of the actual ecosystem. Ecosystems can behave differently in the real-world. 4. Explain the role of keystone species in the stability of ecosystems A keystone species is an organism that helps define an entire ecosystem. When the population of a keystone species declines or becomes imbalanced, it can trigger a cascade of ecological effects. 5. Evaluate the sustainability of resource harvesting from natural ecosystems Sustainable harvesting considers the stability of ecosystems as its primary goal. But if the harvesting rate becomes higher than their renewing rate, due to decreased population size and diversity, ecosystems may become unstable with less resilience. Assessing the sustainability of harvesting activities from ecosystems is crucial to ensure the long-term viability of renewable resources. 6. Outline the factors affecting the sustainability of agriculture Soil erosion: removal of vegetation reduces the productive cover of the soil Agrochemicals: the use of synthetic fertilisers leads to a decline in soil matter Water use: inefficient use of water leads to a loss of water-soluble plant nutrients from the soil Biodiversity: intensive agricultural practises leading to the loss of diversity Carbon footprint: emissions from agricultural activities lead to higher concentrations of greenhouse gases. 7. Explain eutrophication and its effects on ecosystems Eutrophication is the process by which water bodies become enriched with excessive nutrients, particularly nitrogen and phosphorus, leading to an overgrowth of algae and other aquatic plants. This excessive growth can disrupt the balance of the ecosystem and have detrimental effects on water quality, aquatic life and overall ecosystem health. 8. Outline biomagnification of pollutants Biomagnification - process by which toxins are passed from one trophic level to the next within the food web. 9. Describe the effects of microplastic and macroplastic pollution of the oceans Disruptions of marine food webs: transfer of microplastics Chemical pollution: plastics can release harmful chemicals Wildlife entanglement and ingestion: plastics can cause injuries for animals Habitat degradation: as there is more and more plastic it can damage sensitive habitats. 10. Describe the strategies for restoration of natural processes in ecosystems by rewilding Rewilding - involves reintroducing and restoring natural processes and biodiversity to ecosystems that have been degraded or altered by human activities. Species reintroduction: This may involve bringing back keystone species. Habitat restoration: aims to provide suitable conditions for native species to thrive and facilitate natural processes within ecosystems (removing invasive species). Rewilding urban areas: Urban rewilding initiatives aim to increase biodiversity, improve air and water quality, and provide opportunities for people to connect with nature in urban settings (creating green spaces). Rewilding rivers and waterways: removing barriers such as dams or weirs, restoring meanders and allowing rivers to flow more naturally. Ecological management and natural processes: minimising human impacts, such as reducing intensive farming practices, reducing pesticide use and allowing natural successional processes to take place.