Food Webs & Biogeochemical Cycles - D1.pdf

Target: Mul ple choice Ques ons Review notes Food Webs and different rela onships. A food chain shows how energy and nutrients flow from one organism to another in an ecosystem. -In a food chain, each organism is eaten by the next one. It starts with producers (like plants) and moves up to consumers...

Target: Mul ple choice Ques ons Review notes Food Webs and different rela onships. A food chain shows how energy and nutrients flow from one organism to another in an ecosystem. -In a food chain, each organism is eaten by the next one. It starts with producers (like plants) and moves up to consumers (animals that eat plants or other animals). Example: Sun → Grass (Producer) → Rabbit (Primary consumer) → Fox (Secondary consumer) A food web is a more complex version of a food chain. It shows how many food chains in an ecosystem are interconnected. -Many organisms are part of different food chains, so a food web shows a network of multiple feeding relationships. Example: A plant might be eaten by several herbivores, and those herbivores might be eaten by different predators. The arrows show the flow of energy. 3. Types of Relationships between organisms Predation: One organism (the predator) kills and eats another (the prey). Example: Lion (predator) eats a zebra (prey). Competition: Two organisms compete for the same resource (food, shelter, etc.), which can harm both. Example: Two birds fighting over the same tree for nesting space. Mutualism: Both organisms benefit from the relationship. Example: Bees and flowers. Bees get nectar, and flowers get pollinated. Commensalism: One organism benefits, and the other is neither helped nor harmed. Example: Birds eating insects stirred up by a grazing cow. The bird benefits, but the cow is unaffected. Parasitism: One organism benefits at the expense of the other. Example: A tick on a dog. The tick feeds on the dog’s blood, harming the dog. Key Differences: Food Chain: A simple, straight line showing energy flow. Food Web: A complex network of many interconnected food chains. Relationships: These describe how organisms interact, either helping, harming, or having no effect on each other. The Biogeochemical Cycle The biogeochemical cycle refers to the movement of elements and compounds between living organisms (biological), the Earth (geological), and the atmosphere (chemical). These cycles ensure that essential elements like carbon, nitrogen, oxygen, and water are recycled through the environment, making them available for all living organisms. Here’s a simple breakdown for your exam: 1. Water Cycle (Hydrological Cycle)- is the continuous movement of water on, above, and below the surface of the Earth. Stages: Evaporation: Water from oceans, lakes, and rivers turns into vapor and rises into the air. Condensation: Water vapor cools and forms clouds. Precipitation: Water falls from the clouds as rain, snow, or hail. Infiltration: Water soaks into the ground to replenish groundwater. Transpiration: Plants release water vapor through their leaves. Runoff: Water moves across the ground and into rivers, lakes, or oceans. 2. Carbon Cycle- is the process by which carbon moves between the atmosphere, organisms, and the Earth’s surface. Stages: Photosynthesis: Plants take in carbon dioxide (CO₂) from the air and convert it into glucose (food). Respiration: Organisms (plants and animals) release CO₂ back into the atmosphere when they breathe. Decomposition: Dead organisms break down, releasing carbon into the soil or atmosphere. Fossil Fuels: Carbon from plants and animals gets stored in the Earth as coal, oil, and natural gas. When burned, it releases CO₂. 3. Nitrogen Cycle - The movement of nitrogen through the atmosphere, soil, and living organisms. Stages: Nitrogen Fixation: Certain bacteria convert nitrogen gas (N₂) from the air into ammonia (NH₃), which plants can use. Nitrification: Bacteria in the soil convert ammonia into nitrites (NO₂) and then into nitrates (NO₃), which plants absorb. Note: Lightning breaks apart nitrogen molecules (N₂) in the atmosphere, allowing them to react with oxygen and form nitrogen oxides. These compounds mix with water, creating nitrates that fall to the ground in rain. Plants can then absorb these nitrates, making nitrogen available for the ecosystem. Assimilation: Plants take in nitrates to build proteins and amino acids, which animals consume when they eat plants. Ammonification: Decomposers break down dead plants and animals, releasing ammonia back into the soil. Denitrification: Bacteria convert nitrates back into nitrogen gas (N₂), releasing it into the atmosphere. 4. Phosphorus Cycle - The movement of phosphorus through the Earth’s systems (rock, soil, water, and living organisms). Stages: Weathering: Phosphorus is released from rocks into the soil and water through weathering Absorption: Plants absorb phosphorus from the soil. Animals get phosphorus by eating plants or other animals. Decomposition: When plants and animals die, decomposers break down their bodies, releasing phosphorus back into the soil. Sedimentation: Phosphorus can settle into the ocean and eventually form new rocks. Key Points: Biogeochemical cycles are important because they recycle essential elements (water, carbon, nitrogen, phosphorus) that support life. These cycles are interconnected, meaning changes in one cycle can affect the others. Human activities (like burning fossil fuels, farming, and deforestation) can disrupt these cycles, leading to environmental issues. Ecological Succession Ecological succession is the process by which ecosystems change and develop over time. It involves the gradual replacement of one community of organisms by another. There are two main types of ecological succession: primary succession and secondary succession. Here's a simple breakdown for your exam: 1. Primary Succession - The process that occurs in an area where no soil exists, such as on bare rock, after a volcanic eruption, or when a glacier retreats. Stage 1 - Pioneer Species: The first organisms to colonize the area are called pioneer species. These are often small, hardy plants or lichens that can grow in poor, rocky soil. Stage 2 - Soil Formation: As pioneer species grow, they break down the rock, slowly forming soil. Their decay also adds organic matter, enriching the soil. Stage 3 - Intermediate Species: Over time, more plants like grasses and shrubs can grow, as the soil improves. Animals like insects, small mammals, and birds may appear. Stage 4 - Climax Community: Eventually, a stable and mature ecosystem forms, often a forest or a grassland, depending on the region. This is the climax community, where species are in balance and there is little change unless disrupted by an external factor. Example: A volcanic island that is slowly colonized by moss, then grasses, shrubs, and eventually trees, developing into a forest. 2. Secondary Succession - The process that occurs in an area where a disturbance has destroyed an existing ecosystem but left the soil intact. It happens more quickly than primary succession. Stage 1 - Early Growth: After a disturbance (like a forest fire, flood, or farming), the first plants to grow are often grasses and small plants. These are similar to the pioneer species in primary succession. Stage 2 - Intermediate Species: As time passes, shrubs and small trees start to grow, and animals return. Stage 3 - Climax Community: The ecosystem reaches a mature state, similar to how it was before the disturbance, depending on the type of ecosystem (forest, grassland, etc.). Example: After a forest fire, grasses and shrubs grow back first, followed by larger trees, until the forest returns to its previous state. Key Differences Between Primary and Secondary Succession: Primary Succession: Starts with bare rock or no soil, Takes a long time (hundreds to thousands of years), Begins with pioneer species like lichens or mosses. Secondary Succession: Starts with soil already in place, Happens more quickly (decades to centuries), Begins with grasses and small plants, followed by shrubs and trees. Stages of Both Succession Types: 1. Pioneer Stage: First organisms to colonize. 2. Establishment Stage: Plants begin to grow and soil forms. 3. Mature Stage (Climax Community): A stable and mature ecosystem forms. Why It's Important: Ecological succession is important because it helps ecosystems recover after disturbances (natural or human-made) and leads to the development of new habitats and biodiversity. Photosynthesis What is Photosynthesis? - Photosynthesis is the process by which plants use sunlight to make food (glucose) and produce oxygen. It happens in the chloroplasts of plant cells, using chlorophyll (the green pigment). Photosynthesis Formula: 6CO2+6H2O+light energy⟶C6H12O6+6O2 CO₂ (carbon dioxide) comes from the air. H₂O (water) is absorbed by the roots. Glucose (C₆H₁₂O₆) is the plant’s food. Oxygen (O₂) is released into the air. Steps of Photosynthesis: 1. Light-dependent reactions: Light energy splits water molecules, producing oxygen, and creates energy molecules (ATP and NADPH). 2. Calvin Cycle: ATP and NADPH are used to convert carbon dioxide into glucose. Importance: Provides energy for plants. Releases oxygen for animals and humans. Supports food chains, as plants are the base for all ecosystems. Factors that Affect Photosynthesis: Light: More light = more photosynthesis. CO₂: More carbon dioxide = faster photosynthesis. Temperature: Works best within certain temperatures. Water: Plants need water for photosynthesis. Popula on and Popula on Curves A population is a group of individuals of the same species living in the same area at the same time. Population curves show how the size of a population changes over time. They can help us understand growth patterns and how populations interact with their environment. There are different types of population growth curves: 1. Exponential Growth Curve (J-shaped curve) - This curve shows rapid population growth when resources are unlimited (ideal conditions). How it works: Each individual in the population reproduces quickly, and the population grows faster and faster. Example: Bacteria in a lab experiment or invasive species in a new environment. Characteristics: Unlimited resources: No factors limit growth. Rapid growth: The population grows faster over time. Graph: Starts slow, then curves sharply upwards (J-shape). 2. Logistic Growth Curve (S-shaped curve) - This curve shows population growth that starts rapidly but slows down as the population reaches the carrying capacity (the maximum number of individuals the environment can support). How it works: As resources become limited (food, space, etc.), growth slows down and the population stabilizes at a certain level. Characteristics: Carrying capacity: The environment’s limit for population size. Slowed growth: Population growth slows as it nears the carrying capacity. Graph: Starts steep like exponential growth, then flattens as it reaches the carrying capacity (S-shape). 3. Constant Growth (Overshoot and Dieback) - Sometimes populations can overshoot the carrying capacity, growing too large too quickly. This can lead to a dieback, where the population crashes because resources are exhausted or there’s not enough food, leading to a sharp decline. Key Factors Affecting Population Growth: Biotic factors: Things like birth rate and death rate that affect population size. Abiotic factors: Environmental conditions like climate, food availability, and space. Density-dependent factors: Factors that affect population based on its size, like disease or competition. Density-independent factors: Factors that affect populations regardless of size, like natural disasters. Summary: Exponential Growth (J-shaped): Fast, unchecked growth with unlimited resources. Logistic Growth (S-shaped): Growth slows down as the population approaches the carrying capacity of the environment. Density Dependence and Density Independence Density-dependent and density-independent factors are two types of factors that affect the growth and size of populations. They differ in how they impact populations based on their density or size. Density-Dependent Factors - These are factors that affect a population more strongly as its density (size) increases. The larger the population, the more intense the effect of these factors. Examples: Competition: More individuals mean more competition for limited resources (food, water, space). Predation: In larger populations, predators can find and consume more prey. Disease: Crowded populations lead to easier spread of diseases and parasites. Territoriality: As population density increases, there may not be enough space for everyone, leading to conflicts or exclusion. Waste Accumulation: More individuals produce more waste, which can negatively affect the environment and health of the population. Key Idea: The impact of these factors depends on how dense the population is (i.e., how many individuals are in a given area). Density-Independent Factors - These are factors that affect populations regardless of their size or density. These factors influence the population size in the same way, no matter how large or small the population is. Examples: Natural Disasters: Events like hurricanes, wildfires, earthquakes, or floods can drastically reduce a population, regardless of how many individuals are present. Climate: Extreme weather conditions (e.g., droughts, cold spells) can affect populations without regard to their density. Human Activities: Pollution, habitat destruction, or deforestation can affect populations regardless of size. Key Idea: The effect of these factors is not related to the population size, but rather to external environmental conditions. Key Differences: Density-Dependent Factors: The impact increases as population size or density increases (e.g., competition, disease, predation). Density-Independent Factors: The impact is the same regardless of population size (e.g., natural disasters, climate, pollution). Summary: Density-Dependent: The larger the population, the stronger the effect (e.g., food competition, disease). Density-Independent: The effect is the same regardless of population size (e.g., weather, natural disasters). Water Pollu on Water pollution is the contamination of water bodies (rivers, lakes, oceans, groundwater) by harmful substances that negatively affect the quality of water and the organisms living in it. It is caused by human activities and natural events, and it has a major impact on ecosystems, human health, and the environment. Types of Water Pollution: 1. Chemical Pollution -The introduction of harmful chemicals into water sources. These chemicals can poison aquatic life, disrupt ecosystems, and contaminate drinking water. Examples: Pesticides, fertilizers, industrial waste, heavy metals (like mercury and lead), oil spills. 2. Biological Pollution - The presence of harmful microorganisms or pathogens in water. These can cause diseases in humans and animals, such as gastrointestinal issues, cholera, or dysentery. Examples: Bacteria, viruses, parasites (like E. coli or cholera bacteria). 3. Nutrient Pollution: Excessive nutrients (like nitrogen and phosphorus) in the water, often from agricultural runoff. This causes eutrophication, where algae grow rapidly (algal blooms), depleting oxygen and harming aquatic life. Examples: Fertilizers, animal waste, sewage. 4. Physical Pollution - Pollution that physically disrupts water quality. Sediment can block sunlight and reduce oxygen in the water, while plastics and trash harm marine life. Examples: Sediment, plastics, trash. 5. Thermal Pollution - When industries or power plants release hot water into rivers or lakes. Warmer water can lower oxygen levels, harming fish and other aquatic organisms. Sources of Water Pollution: Industrial Waste: Factories releasing chemicals and toxins into rivers or oceans. Agricultural Runoff: Fertilizers, pesticides, and animal waste from farms entering water systems. Sewage and Wastewater: Improperly treated sewage or wastewater from homes, businesses, or industries. Oil Spills: Accidental releases of oil into oceans or rivers, harming marine life. Plastic Pollution: Single-use plastics and waste entering water bodies. Effects of Water Pollution: Harm to Aquatic Life: Pollutants can poison or kill fish, plants, and other organisms. It can also disrupt food chains. Human Health Risks: Contaminated water can cause diseases like cholera, dysentery, and other waterborne illnesses. Ecosystem Damage: Pollutants can damage ecosystems, causing long-term effects on biodiversity and water quality. Economic Impact: Polluted water affects industries like fishing and tourism, and cleaning polluted water is costly. Ways to Prevent and Reduce Water Pollution: 1. Proper Waste Disposal: Dispose of chemicals, trash, and plastics responsibly, and avoid dumping waste into water bodies. 2. Use of Eco-friendly Products: Use biodegradable products and reduce chemical usage in farming. 3. Wastewater Treatment: Ensure wastewater is treated properly before being released into water bodies. 4. Conservation Efforts: Protect wetlands, forests, and other natural areas that help filter and purify water. 5. Public Awareness: Educate people about the importance of clean water and how to reduce pollution. Summary: Water pollution is the contamination of water by harmful substances, including chemicals, waste, and pathogens. It harms aquatic life, ecosystems, and human health. Preventing water pollution involves reducing waste, treating wastewater, and promoting sustainable practices. Water Cycle The water cycle (also called the hydrological cycle) is the continuous movement of water within the Earth’s atmosphere and on its surface. It involves processes that move water through different stages, including evaporation, condensation, precipitation, and infiltration. Here's a simple breakdown for your exam: Main Steps of the Water Cycle: 1. Evaporation: Water from oceans, lakes, rivers, and other bodies of water turns into water vapor due to the heat from the sun. Mostly from oceans, but also from land and plants (through transpiration). It moves water into the atmosphere. 2. Condensation: Water vapor cools down and turns back into liquid form, creating clouds. In the atmosphere, as water vapor cools at higher altitudes. It forms clouds, which store water that will fall back to the Earth. 3. Precipitation: Water falls from clouds in the form of rain, snow, sleet, or hail. From the clouds in the atmosphere to the Earth’s surface. It replenishes water in rivers, lakes, and groundwater. 4. Infiltration: Water soaks into the soil and replenishes groundwater supplies. On the land surface. It helps fill underground water reservoirs, like aquifers. 5. Runoff: Water flows over the surface of the land, eventually returning to rivers, lakes, or oceans. On the surface of the land, especially after rain. It carries water back to the bodies of water, continuing the cycle. 6. Transpiration (part of Evaporation): Water is absorbed by plant roots and released as water vapor through leaves. In plants, especially trees and other vegetation. It contributes to the water vapor in the atmosphere. The water cycle is crucial for maintaining the Earth's water supply, regulating weather, and supporting life.