Conservation Teaching Notes - Unit 9 PDF

C4.2 Transfers of Energy and Matter A4.2 Conservation of Biodiversity 1  Learning Objectives C4.2 Transfers of Energy and Matter SL/HL: 5 hours Guiding questions What is the reason matter can be recycled in ecosystems, but energy can...

C4.2 Transfers of Energy and Matter A4.2 Conservation of Biodiversity 1  Learning Objectives C4.2 Transfers of Energy and Matter SL/HL: 5 hours Guiding questions What is the reason matter can be recycled in ecosystems, but energy cannot? How is the energy that is lost by each group of organisms in an ecosystem replaced? Understandings 🙂 🙁 C4.2.1—Ecosystems as open systems in which both energy and matter can enter and exit. Know that in closed systems only energy is able to pass in and out. C4.2.2—Sunlight as the principal source of energy that sustains most ecosystems. Include exceptions such as ecosystems in caves and below the levels of light penetration in oceans. NOS: Laws in science are generalised principles, or rules of thumb, formulated to describe patterns observed in nature. Unlike theories, they do not offer explanations, but describe phenomena. Like theories, they can be used to make predictions. Should be able to outline the features of useful generalisations. C4.2.3—Flow of chemical energy through the food chain. Appreciate that chemical energy passes to a consumer as it feeds on an organism that is the previous stage in a food chain. C4.2.4—Construction of food chains and food webs to represent feeding relationships in a community. Represent relationships in a local community if possible. Arrows indicate the direction of transfer of energy and biomass. C4.2.5—Supply of energy to decomposers as carbon compounds in organic matter coming from dead organisms Include faeces, dead parts of organisms and dead whole organisms. C4.2.6—Autotrophs as organisms that use external energy sources to synthesise carbon compounds from simple inorganic substances. Understand that energy is required for carbon fixation and for the anabolic reactions that build macromolecules. C4.2.7—Use of light as the external energy source in photoautotrophs and oxidation reactions as the energy source in chemoautotrophs. Understand that oxidation reactions release energy, so 2 they are useful in living organisms. Include iron-oxidising bacteria as an example of a chemoautotroph. C4.2.8—Heterotrophs as organisms that use carbon compounds obtained from other organisms to synthesise the carbon compounds that they require. Appreciate that complex carbon compounds such as proteins and nucleic acids are digested either externally or internally and are then assimilated by constructing the carbon compounds that are required. C4.2.9—Release of energy in both autotrophs and heterotrophs by oxidation of carbon compounds in cell respiration. You are not required to be familiar with photoheterotrophs. C4.2.10—Classification of organisms into trophic levels Use the terms “producer”, “primary consumer”, “secondary consumer” and “tertiary consumer”. Students should appreciate that many organisms have a varied diet and occupy different trophic levels in different food chains. C4.2.11—Construction of energy pyramids. Application of skills: Students should use research data from specific ecosystems to represent energy transfer and energy losses between trophic levels in food chains. C4.2.12—Reductions in energy availability at each successive stage in food chains due to large energy losses between trophic levels. Decomposers and detritus feeders are not usually considered to be part of food chains. However, understand the role of these organisms in energy transformations in food chains. Consider the causes of energy loss. C4.2.13—Heat loss to the environment in both autotrophs and heterotrophs due to conversion of chemical energy to heat in cell respiration. Include the idea that energy transfers are not 100% efficient so heat is produced both when ATP is produced in cell respiration and when it is used in cells. C4.2.14—Restrictions on the number of trophic levels in ecosystems due to energy losses. At each successive stage in food chains there are fewer organisms or smaller organisms. There is therefore less biomass, but the energy content per unit mass is not reduced. C4.2.15—Primary production as accumulation of carbon compounds in biomass by autotrophs. The units should be mass (of carbon) per unit area per unit time and are usually g m−2 yr−1. Understand that biomes vary in their capacity to accumulate biomass. Biomass accumulates when autotrophs and heterotrophs grow or reproduce. C4.2.16—Secondary production as accumulation of carbon compounds in biomass by heterotrophs. Should understand that, due to loss of biomass when carbon compounds are converted to carbon dioxide and water in cell respiration, secondary production is lower than primary production in an ecosystem. C4.2.17—Constructing carbon cycle diagrams. Should illustrate with a diagram how carbon is recycled in ecosystems by photosynthesis, feeding and respiration. C4.2.18—Ecosystems as carbon sinks and carbon sources. If photosynthesis exceeds respiration there is a net uptake of carbon dioxide and if respiration exceeds photosynthesis there is a net release of carbon dioxide. 3  C4.2.19—Release of carbon dioxide into the atmosphere during combustion of biomass, peat, coal, oil and natural gas. Should appreciate that these carbon sinks vary in date of formation and that combustion following lightning strikes sometimes happens naturally but that human activities have greatly increased combustion rates. C4.2.20—Analysis of the Keeling Curve in terms of photosynthesis, respiration and combustion. Include analysis of both the annual fluctuations and the long-term trend. C4.2.21—Dependence of aerobic respiration on atmospheric oxygen produced by photosynthesis, and of photosynthesis on atmospheric carbon dioxide produced by respiration. The fluxes involved per year are huge, so this is a major interaction between autotrophs and heterotrophs. C4.2.22—Recycling of all chemical elements required by living organisms in ecosystems. Should appreciate that all elements used by living organisms, not just carbon, are recycled and that decomposers play a key role. Students are not required to know details of the nitrogen cycle and other nutrient cycles. each objective and are happy with the content by adding a tick in the column marked sure about understandings then make a tick in the column marked 🙂 As you work your way through each learning objective in the booklet, indicate that you have completed 🙁. If you are not and note down any questions that you many have in the space provided. It’s your responsibility to approach your teacher and ask for clarification on any objectives that you do not understand. Space for questions: ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… 4 ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… 5  GLOSSARY Ecosystem: A community of living organisms interacting with each other and their physical environment, where energy and matter can enter and exit. Biome: A large geographical area characterised by specific climate conditions, plant communities, and animal populations. Each biome supports distinct ecosystems and includes environments such as tropical rainforests, deserts, tundras, and grasslands. Open System: An ecosystem in which both energy and matter can enter and exit. Closed System: A system where only energy can pass in and out, but matter remains constant. Sunlight: The principal source of energy that sustains most ecosystems. Gross Primary Productivity (GPP): The total amount of energy captured as biomass by primary producers in an ecosystem. Net Primary Productivity (NPP): The energy that remains after subtracting the energy used for respiration from GPP. It represents the energy available to consumers at higher trophic levels. NPP = GPP - R (where R is respiration losses). Food Chain: A linear sequence of organisms where each is fed upon by the next in the chain, representing the flow of energy and nutrients. Food Web: A complex network of interconnected food chains within an ecosystem, showing the multiple feeding relationships among organisms. Energy Pyramid: A graphical representation of energy flow in an ecosystem, showing the energy transfer and losses between trophic levels. Autotrophs: Organisms that use external energy sources (e.g., sunlight in photoautotrophs, oxidation reactions in chemoautotrophs) to synthesise carbon compounds from simple inorganic substances. Heterotrophs: Organisms that obtain carbon compounds from other organisms to synthesise the carbon compounds they need. Decomposers: Organisms that break down dead organic matter, recycling nutrients back into the ecosystem. Carbon Cycle: The process by which carbon is recycled in ecosystems, involving photosynthesis, feeding, respiration, and decomposition. Carbon Sink: An ecosystem that absorbs more carbon dioxide than it releases, typically through processes like photosynthesis. Carbon Source: An ecosystem that releases more carbon dioxide than it absorbs, often due to respiration or combustion. Keeling Curve: A graph showing the concentration of atmospheric carbon dioxide over time, indicating both short-term fluctuations and long-term trends. Aerobic Respiration: The process by which cells use oxygen to convert carbon compounds into energy, releasing carbon dioxide as a byproduct. Photosynthesis: The process by which photoautotrophs convert light energy, carbon dioxide, and water into 6 glucose and oxygen. Primary Production: The accumulation of carbon compounds in biomass by autotrophs, measured in units of mass per unit area per unit time (e.g., g m⁻² yr⁻¹). Secondary Production: The accumulation of carbon compounds in biomass by heterotrophs, which is lower than primary production due to respiratory losses. Trophic Levels: The hierarchical levels in a food chain, categorised as producers, primary consumers, secondary consumers, and tertiary consumers. Heat Loss: The loss of energy in the form of heat during metabolic processes such as cell respiration, which reduces the energy available at higher trophic levels. Combustion: The process of burning biomass, peat, coal, oil, or natural gas, which releases carbon dioxide into the atmosphere. Recycling of Elements: The continuous cycling of all chemical elements required by living organisms (e.g., carbon, nitrogen) within ecosystems, with decomposers playing a key role. Photoautotrophs: Autotrophs that use light as their external energy source for photosynthesis. Chemoautotrophs: Autotrophs that use oxidation reactions of inorganic molecules as their energy source, such as iron-oxidising bacteria. ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… 7 Open and Closed Systems C4.2.1—Ecosystems as open systems in which both energy and matter can enter and exit. Know that in closed systems only energy is able to pass in and out. Open System: Can exchange both matter and Closed System: Can exchange only energy energy with surroundings. with surroundings. Examples of open systems (to help you put into Examples of closed systems (to help you put context). into context). The human body. The Earth is a closed system. It receives Car engine. lots of energy from the Sun but there is A beaker of water where water can no exchange of matter evaporate and the beaker does not insulate inside at all. Ecosystems as open systems Definition: Ecosystems are open systems where both energy and matter can be exchanged with the environment. Matter Recycling: Matter is cycled through various processes, including decomposition and nutrient uptake. Decomposers break down organic material, recycling nutrients back into the soil. Energy Flow: Energy enters ecosystems primarily as sunlight and exits as heat. This energy transfer occurs through feeding relationships and metabolic processes. Closed Systems: In theoretical closed systems, only energy can be exchanged, with no matter entering or exiting the system. 8 Sunlight as the principle source of energy C4.2.2—Sunlight as the principal source of energy that sustains most ecosystems. Include exceptions such as ecosystems in caves and below the levels of light penetration in oceans. NOS: Laws in science are generalised principles, or rules of thumb, formulated to describe patterns observed in nature. Unlike theories, they do not offer explanations, but describe phenomena. Like theories, they can be used to make predictions. Should be able to outline the features of useful generalisations. Sunlight: Is the primary energy source for most ecosystems, driving photosynthesis in plants and other photoautotrophs. Photosynthesis: Plants, algae, and some bacteria use sunlight to convert carbon dioxide and water into glucose and oxygen. Exceptions: Chemosynthesis of bacteria and archaea in hydrothermal vents and caves. Deep-sea hydrothermal vents on the ocean floor Some bacteria and archaea oxidise hydrogen sulphide (H₂S), abundant in the superheated water released by hydrothermal vents, to generate energy. H2S+O2→SO42−+H2O+energy The energy produced is used to fix carbon dioxide (CO₂) into organic compounds, which these bacteria can use as food. Caves with high ammonia concentrations, such as those that accumulate from bat guano (bat droppings). Nitrifying bacteria oxidise ammonia (NH₃) to nitrite (NO₂⁻) and then to nitrate (NO₃⁻), releasing energy in the process. NH3+O2→NO2−+H2O+energy The energy produced is used to fix carbon dioxide (CO₂) into organic compounds, which these bacteria can use as food. 9 C4.2.3—Flow of chemical energy through the food chain. Appreciate that chemical energy passes to a consumer as it feeds on an organism that is the previous stage in a food chain. Chemical energy is transferred from one organism to another through feeding relationships in a food chain. Energy Transfer: Energy stored in plant biomass (producers) is passed to herbivores (primary consumers) and then to carnivores (secondary and tertiary consumers). Energy Loss: At each trophic level, a significant amount of energy is lost as heat, limiting the amount of energy available to higher trophic levels. Food chains and food webs C4.2.4—Construction of food chains and food webs to represent feeding relationships in a community. Represent relationships in a local community if possible. Arrows indicate the direction of transfer of energy and biomass. Food Chains A food chain is a linear sequence of organisms where each one is eaten by the next. (Feeding relationships) It shows the flow of energy and biomass from one organism to another. The direction of the arrows represent the direction the energy is flowing. In the space provided, construct your own food chain. Can you think of one typical in KSA? 10 Food webs: A food web is a network of interconnected food chains that shows the feeding relationships between different organisms in an ecosystem as many organisms have more than one food source or predator. A food web better represents the complexity of real ecosystems compared to a simple, linear food chain. Using the food web provided can you give examples of the following: Producer:.................................................................. Primary consumer:.................................................................................................................................................................................. Secondary consumer: ………………………………………………………………. ………………………………………………………………. Tertiary consumer: ………………………………………………………………. ………………………………………………………………. Can you identify a consumer that exists on two different trophic levels? ……………………………………………………………… ……………………………………………………………… Simple Food Web Example: Construct your own food web in the space provided using the following instructions: Habitat: Grassland Ecosystem 1. Producers: ○ Grass ○ Shrubs 2. Primary Consumers (Herbivores): ○ Grasshopper (eats grass) ○ Rabbit (eats grass and shrubs) 3. Secondary Consumers (Carnivores/Omnivores): ○ Frog (eats grasshoppers) ○ Snake (eats frogs and rabbits) 4. Tertiary Consumers (Top Predators): ○ Hawk (eats snakes and rabbits) Food Web Connections: Grass → Grasshopper → Frog → Snake → Hawk Grass → Rabbit → Snake → Hawk Shrubs → Rabbit → Hawk 11 Space for your own grassland food web C4.2.10—Classification of organisms into trophic levels Use the terms “producer”, “primary consumer”, “secondary consumer” and “tertiary consumer”. Should appreciate that many organisms have a varied diet and occupy different trophic levels in different food chains. 12 Decomposers C4.2.5—Supply of energy to decomposers as carbon compounds in organic matter coming from dead organisms Include faeces, dead parts of organisms and dead whole organisms. Decomposers' Role: Decomposers saprotrophs (e.g., bacteria, fungi) and detritivores (worms, insects) break down dead organisms, faeces, and organic matter, releasing nutrients back into the ecosystem. Energy Source: They obtain energy from the decomposition of carbon compounds in dead matter, contributing to nutrient cycling. Q. What is the difference between a saprotroph and a detritivore? 13 Autotrophs synthesise carbon compounds using external energy sources C4.2.6—Autotrophs as organisms that use external energy sources to synthesise carbon compounds from simple inorganic substances. Understand that energy is required for carbon fixation and for the anabolic reactions that build macromolecules. Anabolic reactions build macromolecules (Revision) Energy is Essential: Without the input of external energy, autotrophs cannot fix carbon or build the macromolecules necessary for life. Anabolic Processes Require Energy: Building complex molecules is energetically demanding. Energy drives the synthesis of carbohydrates, proteins, lipids, and nucleic acids from simpler building blocks. Examples of macromolecules essential for life Carbohydrates: Glucose, starch, cellulose. Proteins: Amino acids, enzymes, structural proteins. Lipids: Fatty acids, triglycerides, phospholipids. Nucleic Acids: DNA, RNA. 14 C4.2.7—Use of light as the external energy source in photoautotrophs and oxidation reactions as the energy source in chemoautotrophs. Understand that oxidation reactions release energy, so they are useful in living organisms. Include iron-oxidising bacteria as an example of a chemoautotroph. Energy Source: Photoautotrophs Examples of photoautotrophs include: Plants Algae Cyanobacteria Diatoms Light Energy ➔ Chemical Energy: Chlorophyll in plants and bacteriorhodopsin in some bacteria captures sunlight, which provides the energy needed for carbon fixation during Example: Photosynthesis in plants: Balanced chemical equation for photosynthesis: Energy Sources: Chemoautotrophs Chemoautotrophs use inorganic compounds as energy sources to carry out chemosynthesis. These compounds are oxidised (lose electrons) in chemical reactions to produce energy, which is used to fix carbon dioxide (CO₂) into organic compounds. Iron-oxidising bacteria. Example: Acidithiobacillus ferrooxidans Found in acidic environments, iron-rich soils, hydrothermal vent systems. They oxidise ferrous iron (Fe²⁺) to ferric iron (Fe³⁺), releasing energy for carbon fixation. Chemical Reaction: 15 Heterotrophs and Carbon Compounds C4.2.8—Heterotrophs as organisms that use carbon compounds obtained from other organisms to synthesise the carbon compounds that they require. Appreciate that complex carbon compounds such as proteins and nucleic acids are digested either externally or internally and are then assimilated by constructing the carbon compounds that are required. Heterotrophs are organisms that cannot produce their own food and must obtain carbon compounds (such as carbohydrates, proteins, and lipids) by consuming other organisms. Sources of Carbon Compounds: Heterotrophs rely on plants, animals, or other organisms to obtain organic carbon compounds, which they break down and use to build their own molecules. Digestion of Complex Carbon Compounds: Heterotrophs digest complex molecules like proteins and nucleic acids into smaller molecules: ○ Proteins are broken down into amino acids. ○ Nucleic acids (DNA/RNA) are broken down into nucleotides. Digestion can be: ○ External: In organisms like fungi that release digestive enzymes into the environment to break down large molecules. ○ Internal: In most animals, digestion occurs within specialised organs like the stomach and intestines. Assimilation of Carbon Compounds: After digestion, the smaller molecules (amino acids, sugars, etc.) are absorbed by cells. These molecules are then assimilated (converted) into complex molecules required by the organism: ○ Amino acids are used to synthesise proteins. ○ Nucleotides are used to construct nucleic acids (DNA/RNA). ○ Sugars and fats are used for energy or stored for future use. 16 Oxidation of carbon compounds is the same in both autotrophs and heterotrophs C4.2.9—Release of energy in both autotrophs and heterotrophs by oxidation of carbon compounds in cell respiration. You are not required to be familiar with photoheterotrophs. Cell respiration involves the oxidation of carbon compounds to release energy, producing ATP and CO₂ as byproducts. This process occurs in both autotrophs (using glucose made from photosynthesis) and heterotrophs (using glucose obtained from food). Energy released is primarily stored as ATP for cellular functions, with some energy lost as heat. 17 Construction of an Energy Pyramid C4.2.11—Construction of energy pyramids. Application of skills: Should use research data from specific ecosystems to represent energy transfer and energy losses between trophic levels in food chains. Instructions for Constructing a Scaled Energy Pyramid 1. Determine Energy Values: ○ Identify the energy available at each trophic level from your data. This typically includes: Producers (e.g. plants) Primary consumers (e.g. herbivores) Secondary consumers (e.g. carnivores) Tertiary consumers (e.g. apex predators) Decomposers 2. Scale the Pyramid: ○ Decide on a scale for your pyramid. For example, 1 cm on your pyramid could represent 1,000 kJ/m²/yr (you may have to scale this down in order for it to fit the page!) ○ Convert the energy values at each trophic level into appropriate widths for your pyramid sections based on your chosen scale. 3. Draw the Pyramid: ○ Start with the base (producers) and work upwards. Each level should be narrower than the one below it, reflecting the decrease in energy as you move up the trophic levels. ○ Label each section with the trophic level and the corresponding energy value. 4. Indicate Energy Losses: ○ Use arrows or notes to indicate the energy lost between each level (e.g., as heat through respiration, waste). EXAMPLE: Energy Pyramid from a Grassland Ecosystem Trophic Levels and Energy Values (example data): Construct your own energy pyramid using the example provided. Producers: Grasses, energy available = 130,000 kJ/m²/yr Primary Consumers - Herbivores: grasshoppers, energy available = 13,000 kJ/m²/yr Secondary Consumers - Small carnivores: Song thrush, energy available = 1,800 kJ/m²/yr Tertiary Consumers - Apex predators: hawks, energy available = 300 kJ/m²/yr Decomposers - Bacteria and fungi: 15,500 = kJ/m²/yr Use the space provided to construct your energy pyramid. Remember to: ➔ Include labels and energy values (kJ/m²/yr) available for each trophic level. ➔ Add arrows to illustrate how energy is lost at each trophic level. 18 Construct your scaled energy pyramid here. Always start with the PRODUCER. 19 Energy losses between trophic levels C4.2.12—Reductions in energy availability at each successive stage in food chains due to large energy losses between trophic levels. Decomposers and detritus feeders are not usually considered to be part of food chains. However, understand the role of these organisms in energy transformations in food chains. Consider the causes of energy loss. Energy losses in producers occur through: Respiration Metabolic heat production Detritus Non edible material Energy losses in consumers occur through: Respiration Metabolic heat production Waste (faeces) Non edible material 20 Role of decomposers and detritus feeders Detritus feeders Decomposers Breaking Down Organic Matter: Decomposers (e.g., bacteria and fungi) and detritus feeders (earthworms, beetles) break down dead organic matter, including plant material, dead animals, and waste products (faeces). Recycling Nutrients: releasing essential nutrients (nitrates) back into the soil and ecosystem for uptake by producers (plants). Energy Transformation: transform the chemical energy stored in dead organisms and waste into forms that can be used within the ecosystem. 21 C4.2.14—Restrictions on the number of trophic levels in ecosystems due to energy losses. At each successive stage in food chains there are fewer organisms or smaller organisms. There is therefore less biomass, but the energy content per unit mass is not reduced. Energy Loss at Each Trophic Level: At each step in a food chain, only about 10% of the energy (10% rule) is transferred to the next trophic level, with the remaining 90% lost as heat, respiration, waste, and other processes. Limitation on Number of Trophic Levels: Energy losses means there is insufficient energy to support many trophic levels. Most ecosystems have 4 to 5 trophic levels, with fewer organisms at higher levels. Decrease in Biomass: As energy is lost, there is less biomass at higher trophic levels. Organisms at these levels tend to be fewer in number or smaller in size. Energy Content Per Unit Mass: Despite the reduction in overall biomass at higher trophic levels, the energy content per unit mass (e.g., in a predator) remains roughly the same as in organisms at lower levels. However, the total available energy decreases. Ecosystem Balance: The restriction on trophic levels ensures a balance within ecosystems, preventing overexploitation of resources and maintaining stability in energy flow and population sizes. 22 ATP Synthesis and USE in Autotrophs and Heterotrophs C4.2.13—Heat loss to the environment in both autotrophs and heterotrophs due to conversion of chemical energy to heat in cell respiration. Include the idea that energy transfers are not 100% efficient so heat is produced both when ATP is produced in cell respiration and when it is used in cells. ATP Synthesis and Use in Autotrophs ATP Synthesis and Use in Heterotrophs Definition: First Law of Thermodynamics Energy cannot be created or destroyed, only transformed from one form to another. Definition: Second Law of Thermodynamics Energy transformations are not 100% efficient; some energy is always lost as heat. ATP Synthesis: Some of the energy released during cellular respiration is used to make ATP. However, not all the energy is captured and stored in ATP. Some is lost as heat to the environment. ATP Use: When cells use ATP to perform work (like muscle contraction, transporting molecules, or building new molecules), the energy from ATP is released. Again, not all of this energy is used for work—some is released as heat to the environment. For additional reading use Kognity link https://app.kognity.com/study/app/ibdp-biology-slhl-2025-pc/sid-422-cid-242422/book/energy-losses-i d-46634/ 23 Primary and Secondary Production C4.2.15—Primary production as accumulation of carbon compounds in biomass by autotrophs. The units should be mass (of carbon) per unit area per unit time and are usually g m−2 yr−1. Understand that biomes vary in their capacity to accumulate biomass. Biomass accumulates when autotrophs and heterotrophs grow or reproduce. C4.2.16—Secondary production as accumulation of carbon compounds in biomass by heterotrophs. Should understand that, due to loss of biomass when carbon compounds are converted to carbon dioxide and water in cell respiration, secondary production is lower than primary production in an ecosystem. Primary Production: The rate at which producers, including plants, algae, and cyanobacteria, accumulate carbon compounds in their biomass. Effectively growing or reproducing offspring. Biomass accumulates as organisms grow or reproduce. Primary productivity is measured in units of mass per unit area per unit time, such as grams (of carbon) per square metre per year (g m−2 yr−1). Secondary Production: Secondary production is the rate at which heterotrophs convert ingested food into new biomass. Measured in units of mass per unit area per unit time, such as grams (of carbon) per square metre per year (g m−2 yr−1). Lower than primary production due to energy losses in respiration (carbon compounds converted into CO2 and water). 24 Gross primary productivity (GPP) vs Net primary productivity (NPP) Gross primary productivity (GPP): Total amount of energy captured as biomass where carbon is converted into organic matter by primary producers in an ecosystem or biome. Not all the energy captured through photosynthesis is stored as biomass. Some energy is used for respiration resulting in energy losses. The energy that remains after subtracting these losses is known as; Net primary productivity (NPP): The energy available to consumers at higher trophic levels supports growth, reproduction, and storage within the ecosystem. Net primary productivity can be calculated by the following equation: NPP = GPP – R NPP – Net primary production GPP – Gross primary production R – Respiration losses 25 Biomes vary in their capacity to accumulate biomass Representation of terrestrial biomes Factors affecting biomass accumulation in different biomes Factor Description Climate Warmer temperatures support faster growth rate in plants Colder climates have slower plant growth rates. Biomes high rainfall (precipitation) accumulates more biomass compared to arid biomes where water scarcity limits plant growth. Nutrient availability Biomes with nutrient-rich soils can support higher rates of biomass accumulation. Biomes with poor soils have lower productivity. Sunlight Biomes near the equator receive consistent and intense sunlight, leading to high biomass accumulation. Polar regions receive less sunlight, resulting in lower biomass. Season Biomes with longer growing seasons have more time for plants to grow and accumulate biomass. Biomes with short growing seasons accumulate less biomass due to limited time for growth. 26 Examples of different biomes. Task 1: Rainforest Arid Desert Climate: Climate: Temperature Temperature Precipitation Precipitation Nutrient availability: Nutrient availability: Sunlight: Sunlight: Seasons: Seasons: Biomass Accumulation: Biomass Accumulation: Tundra Temperate forest Climate: Climate: Temperature Temperature Precipitation Precipitation Nutrient availability: Nutrient availability: Sunlight: Sunlight: Seasons: Seasons: Biomass Accumulation: Biomass Accumulation: Carry out some research of your own on examples of different biomes. When identifying the following criteria Nutrient availability: Sunlight: Biomass Accumulation: You need only suggest HIGH MEDIUM or LOW for each. 27 Task 2: Average net primary productivity (Kg m−2 yr−1) 1. Which examples of biomes show the highest productivity (Kg m−2 yr−1) in terms of biomass? 2. Which examples of biomes show the lowest productivity (Kg m−2 yr−1) in terms of biomass? 3. Suggest reasons why these biomes have high and low biomass productivity (Kg m−2 yr−1). 28 The Carbon Cycle C4.2.17—Constructing carbon cycle diagrams. Should illustrate with a diagram how carbon is recycled in ecosystems by photosynthesis, feeding and respiration. C4.2.18—Ecosystems as carbon sinks and carbon sources. If photosynthesis exceeds respiration there is a net uptake of carbon dioxide and if respiration exceeds photosynthesis there is a net release of carbon dioxide. 29 Constructing carbon cycle diagrams. Should illustrate with a diagram how carbon is recycled in ecosystems by photosynthesis, feeding and respiration. 30 Carbon cycling and photosynthesis Process: Plants, algae, and some bacteria (autotrophs) take in carbon dioxide (CO₂) from the atmosphere during photosynthesis. Carbon Fixation: They use sunlight to convert CO₂ and water into glucose (a carbon-based sugar) and oxygen. Result: Carbon is "fixed" from the atmosphere and incorporated into the biomass of the plant as glucose and other organic molecules. CO2 levels in the atmosphere are approximately 0.04% (400 umol/ mol) CO2 concentrations are lowest where there is high photosynthesis e.g. rain forests. Carbon recycling and feeding Herbivores: eat plants, consuming the carbon compounds (like glucose) stored in the plant biomass. Carnivores: consume carbon compounds stored in the herbivore's biomass. Assimilation: Carbon from the food is used by animals to build their own biomass (like muscles and tissues). Decomposers: When plants and animals die, decomposers like bacteria and fungi break down their remains. Carbon Release: The carbon in the dead organic matter is converted into CO₂ and released into the atmosphere through the decomposers' respiration..Carbon cycling and respiration Cellular Respiration: Both plants and animals release energy from glucose (and other carbon compounds) through cellular respiration. CO₂ Release: During this process, carbon is released back into the atmosphere as carbon dioxide (CO₂), completing the cycle. Energy Use: The energy released is used for various biological processes, but the carbon is returned to the atmosphere. 31 Combustion of biomass, peat and fossil fuels - carbon sinks C4.2.19—Release of carbon dioxide into the atmosphere during combustion of biomass, peat, coal, oil and natural gas. Should appreciate that these carbon sinks vary in date of formation and that combustion following lightning strikes sometimes happens naturally but that human activities have greatly increased combustion rates. Examples of carbon sinks Biomass, peat, coal, and oil & natural gas act as carbon sinks. They store carbon that was once in the atmosphere. Biomass and peat are active carbon sinks in the environment today. Coal and oil & gas represent ancient carbon sinks that have stored carbon for millions of years. Biomass is derived Peat is an accumulation Coal is a fossil fuel Oil & Natural Gas are fossil from living or recently of partially decayed plant formed from the remains fuels that formed over a living organisms, material. of plants that died about 300-400 million years ago 300 million years ago Common examples Forms in waterlogged, Formed in seas and lakes include wood, crop anaerobic conditions, Over time, plant remains from dead marine plankton residues, manure, and (bogs and wetlands) were buried under layers some types of organic which prevents complete of soil and rock, Sediment built up burying waste. decomposition. subjecting it to intense this organic matter, heat and pressure, then subjecting it to intense heat Over thousands of years, transformed into coal. and pressure, then dead plant material builds transformed into oil and gas up and is compressed into peat. Combustion of biomass, peat or fossil fuels Combustion = oxidation of biomass, peat or fossil fuels by burning Products of complete combustion = carbon dioxide & water Burning of fossil fuels and fires to clear tropical rainforest increase CO2 levels in atmosphere Many parts of the world burn biomass as fuel 32 Lightning and Human Activities Human activities, such as deforestation Lightning strikes are natural electrical (logging), slash-and-burn agriculture (use of fire discharges during storms. to clear land for agriculture) and burning of fossil fuels (for industry and transport), have When lightning strikes a dry area, it can increased the rates and intensity of combustion. generate enough heat to ignite vegetation, such as dry grass, leaves, or trees. Leading to higher atmospheric CO₂ emission Carbon stored in the plant biomass is released Contributing significantly to global climate back into the atmosphere as carbon dioxide change and the enhanced greenhouse effect contributing to the carbon cycle. Natural wildfires can promote new growth and maintain ecological balance by preventing the overaccumulation of biomass. To be covered in D4.3 Climate Change The enhanced greenhouse effect: caused by increased levels of greenhouse gases like CO₂ from human activities, traps more heat in the Earth’s atmosphere. This leads to global warming and disrupting ecosystems by: altering habitats, causing species migration, and increasing the frequency of extreme weather events such as heatwaves, storms, and droughts. These changes can harm biodiversity and destabilise ecosystems. 33 The Keeling Curve C4.2.20—Analysis of the Keeling Curve in terms of photosynthesis, respiration and combustion. Include analysis of both the annual fluctuations and the long-term trend. Link to Kognity for reference https://app.kognity.com/study/app/ibdp-biology-slhl-2025-pc/sid-422-cid-242422/book/human-impact-on-the-carb on-cycle-id-46637/ The Keeling curve shows changes in atmospheric carbon dioxide levels measured at the Mauna Loa Observatory in Hawaii (ppmv = parts per million by volume) The yearly fluctuations shown in red are due to seasonal changes in photosynthesis rates, while the overall trend shown in blue is due to human combustion of fossil fuels The graph shows both annual fluctuations and a long-term upward trend in CO₂ levels. (SaveMyExams) Data Analysis: Answer the following question. The Keeling Curve is a graph that shows the concentration of carbon dioxide (CO₂) in ppmv in the atmosphere over time, as measured at the Mauna Loa Observatory in Hawaii. The graph shows both annual fluctuations and a long-term upward trend in CO₂ levels. 34 Above is a simplified version of the Keeling Curve from 1955 to 2010. Use the graph to answer the following questions: 1. Describe the pattern of annual fluctuations in the Keeling Curve. (2 marks) 2. Explain the cause of these annual fluctuations. (3 marks) 3. Describe the long-term trend observed in the Keeling Curve. (2 marks) 4. Discuss how the processes of photosynthesis, respiration, and combustion contribute to the patterns observed in the Keeling Curve. (6 marks) 5. Considering the current trend, suggest one potential consequence for ecosystems if CO₂ levels continue to rise. (2 marks) 35 Dependence of Aerobic Respiration and Photosynthesis C4.2.21—Dependence of aerobic respiration on atmospheric oxygen produced by photosynthesis, and of photosynthesis on atmospheric carbon dioxide produced by respiration. The fluxes involved per year are huge, so this is a major interaction between autotrophs and heterotrophs. Aerobic Respiration: Oxygen Requirement: Aerobic respiration in both autotrophs (like plants) and heterotrophs (like animals) relies on atmospheric oxygen (O₂). Energy Production: Oxygen is essential for breaking down glucose in cells, releasing energy (ATP), carbon dioxide (CO₂), and water (H₂O). Source of Oxygen: The oxygen used in respiration is produced by photosynthesis. Photosynthesis: CO₂ Requirement: Photosynthesis in autotrophs requires carbon dioxide (CO₂) from the atmosphere. Carbon Fixation: Plants, algae, and some bacteria use CO₂ to produce glucose and release oxygen as a byproduct Source of CO₂: The CO₂ required for photosynthesis is produced by the respiration of autotrophs and heterotrophs. Interaction Between Autotrophs and Heterotrophs: Photosynthesis and respiration are tightly linked processes. The oxygen produced by photosynthesis is vital for aerobic respiration, while the CO₂ produced by respiration is necessary for photosynthesis. 36  Carbon Dioxide and Oxygen Fluxes Annual Fluxes: The exchange of CO₂ and O₂ between these processes involves massive atmospheric fluxes each year, maintaining a balance in the Earth’s atmosphere. https://www.algebralab.org/practice/practice.aspx?file=Reading_CO2andO2.xml 37 Recycling of Nitrogen and Phosphorus in Ecosystems C4.2.22—Recycling of all chemical elements required by living organisms in ecosystems. Should appreciate that all elements used by living organisms, not just carbon, are recycled and that decomposers play a key role. You are not required to know details of the nitrogen cycle and other nutrient cycles. Nitrogen Cycle All chemical elements essential for life (e.g., carbon, oxygen, nitrogen, phosphorus) are continuously recycled within ecosystems. Decomposers, such as bacteria and fungi, break down dead organisms and waste products, releasing these elements back into the environment for reuse by other organisms. Example: Nitrogen: required for protein synthesis/nucleic acid synthesis Phosphorus: required for ATP synthesis/nucleic acid synthesis 38  Learning Objectives A4.2 Conservation of Biodiversity SL/HL: 3 hours Guiding questions What factors are causing the sixth mass extinction of species? How can conservationists minimise the loss of biodiversity? Understandings 🙂 🙁 A4.2.1—Biodiversity as the variety of life in all its forms, levels and combinations. Include ecosystem diversity, species diversity and genetic diversity. A4.2.2—Comparisons between current number of species on Earth and past levels of biodiversity. Millions of species have been discovered, named and described but there are many more species to be discovered. Evidence from fossils suggests that there are currently more species alive on Earth today than at any time in the past. NOS: Classification is an example of pattern recognition but the same observations can be classified in A4.2.3—Causes of anthropogenic species extinction. This should be a study of the causes of the current sixth mass extinction, rather than of non-anthropogenic causes of previous mass extinctions. To give a range of causes, carry out three or more brief case studies of species extinction: North Island giant moas (Dinornis novaezealandiae) as an example of the loss of terrestrial megafauna, Caribbean monk seals (Neomonachus tropicalis) as an example of the loss of a marine species, and one other species that has gone extinct from an area that is familiar to students. Note: When referring to organisms in an examination, either the common name or the scientific name is acceptable. A4.2.4—Causes of ecosystem loss. Should study only causes that are directly or indirectly anthropogenic. Include two case studies of ecosystem loss. One should be the loss of mixed dipterocarp forest in Southeast Asia, and the other should, if possible, be of a lost ecosystem from an area that is familiar to students. A4.2.5—Evidence for a biodiversity crisis. Evidence can be drawn from the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem. Services reports and other sources. Results from reliable surveys of biodiversity in a wide range of habitats around the world are required. Students should understand that surveys need to be repeated to provide evidence of change in species richness and evenness. Note that there are opportunities for contributions from both expert scientists and citizen scientists. 39  NOS: To be verifiable, evidence usually has to come from a published source, which has been peer- reviewed and allows methodology to be checked. Data recorded by citizens rather than scientists brings A4.2.6—Causes of the current biodiversity crisis. Include human population growth as an overarching cause, together with these specific causes: hunting and other forms of over-exploitation; urbanisation; deforestation and clearance of land for agriculture with consequent loss of natural habitat; pollution and spread of pests, diseases and invasive alien species due to global transport. A4.2.7—Need for several approaches to conservation of biodiversity. No single approach by itself is sufficient, and different species require different measures. Include in situ conservation of species in natural habitats, management of nature reserves, rewilding and reclamation of degraded ecosystems, ex situ conservation in zoos and botanic gardens and storage of germplasm in seed or tissue banks. A4.2.8—Selection of evolutionarily distinct and globally endangered species for conservation prioritisation in the EDGE of Existence programme.Should understand the rationale behind focusing conservation efforts on evolutionarily distinct and globally endangered species (EDGE). NOS: Issues such as which species should be prioritised for conservation efforts have complex ethical, environmental, political, social, cultural and economic implications and therefore need to be debated. each objective and are happy with the content by adding a tick in the column marked sure about understandings then make a tick in the column marked 🙂 As you work your way through each learning objective in the booklet, indicate that you have completed 🙁. If you are not and note down any questions that you many have in the space provided. It’s your responsibility to approach your teacher and ask for clarification on any objectives that you do not understand. Space for questions: ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… 40 ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… 41  GLOSSARY Biodiversity: The variety of life in all its forms, levels, and combinations, including ecosystem diversity, species diversity, and genetic diversity. Ecosystem Diversity: The variety of ecosystems in a given region or on Earth, each with different species and environmental conditions. Species Diversity: The number of different species and the relative abundance of each species within a given area. Genetic Diversity: The variety of genes within a species or population, which allows for adaptation and survival in changing environments. Mass Extinction: A rapid, widespread decrease in the biodiversity on Earth, where a large number of species go extinct in a short period of time. Sixth Mass Extinction: The ongoing, anthropogenic extinction event driven by human activities, such as habitat destruction, over-exploitation, and climate change, leading to accelerated species loss. Anthropogenic: Caused by human activities. In the context of extinction and ecosystem loss, it refers to human-driven changes that negatively impact biodiversity and ecosystems. North Island Giant Moa (Dinornis novaezealandiae): An extinct species of large, flightless bird native to New Zealand. Its extinction is an example of the loss of terrestrial megafauna, primarily due to overhunting by humans. Caribbean Monk Seal (Neomonachus tropicalis): An extinct species of marine mammal that inhabited the Caribbean Sea. It was driven to extinction due to overhunting and habitat destruction. Ecosystem Loss: The degradation or destruction of ecosystems, often as a result of human activities such as deforestation, urbanisation, and pollution. Mixed Dipterocarp Forest: A type of tropical rainforest found in Southeast Asia, characterised by trees in the Dipterocarpaceae family. This forest is at risk due to deforestation for agriculture, logging, and palm oil plantations. Biodiversity Crisis: The accelerated loss of biodiversity on a global scale, driven by human activities, resulting in the extinction of species and the degradation of ecosystems. Species Richness: The number of different species present in an ecosystem or specific area. Species Evenness: The relative abundance of different species in an ecosystem, which contributes to the overall balance and stability of the ecosystem. Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES): An international organisation that assesses the state of biodiversity and ecosystems, providing evidence and policy recommendations to address global biodiversity challenges. Citizen Science: The practice of public participation and collaboration in scientific research, often involving non-professional volunteers collecting data, which can contribute to biodiversity surveys and monitoring. Over-Exploitation: The excessive use of natural resources, such as hunting, fishing, and logging, leading to the depletion of species and the destruction of ecosystems. 42 Urbanisation: The expansion of cities and human settlements, often leading to habitat destruction, fragmentation, and the displacement of species. Invasive Species: Non-native species introduced to an ecosystem, often by human activities, that outcompete and displace native species, leading to declines in biodiversity. In Situ Conservation: The conservation of species in their natural habitats, including the protection and management of nature reserves and ecosystems to maintain biodiversity. Ex Situ Conservation: The conservation of species outside their natural habitats, such as in zoos, botanical gardens, and seed banks, often used as a backup to prevent species extinction. Rewilding: The process of restoring ecosystems to their natural state by reintroducing native species and removing human influences, aiming to return ecological processes and biodiversity. EDGE of Existence Programme: A conservation initiative that prioritises the protection of Evolutionarily Distinct and Globally Endangered (EDGE) species, which have few close relatives and are at high risk of extinction. Germplasm: Genetic material in the form of seeds, tissues, or cells used for the preservation of genetic diversity in plant and animal species, typically stored in seed or tissue banks. Evolutionarily Distinct and Globally Endangered (EDGE) Species: Species that are both evolutionarily unique and at a high risk of extinction, often targeted for conservation due to their irreplaceable genetic and ecological value. ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………… 43 What is Biodiversity? https://app.kognity.com/study/app/ibdp-biology-slhl-2025-pc/sid-422-cid-242422/book/title-to-come-id-4 3810/ A4.2.1—Biodiversity as the variety of life in all its forms, levels and combinations. Include ecosystem diversity, species diversity and genetic diversity. Genetic diversity in humans Ecosystem diversity: Includes different types of ecosystems such as tropical rainforests, coral reefs, deserts, grasslands, and tundra. Example: Amazon rainforest (terrestrial ecosystem), Great Barrier Reef (marine ecosystem). Species diversity: The variety and abundance of different species in an area. Example: Rainforests have high species diversity, containing thousands of species of plants and animals. Genetic diversity: The variety of genes within a species or population. Example: Genetic variation in populations of macaws. The variations in the population of macaws indicate genetic diversity. 44 Biodiversity Past and Present A4.2.2—Comparisons between current number of species on Earth and past levels of biodiversity. Millions of species have been discovered, named, and described but there are many more species to be discovered. Evidence from fossils suggests that there are currently more species alive on Earth today than at any time in the past. Biodiversity PRESENT Biodiversity PAST Current species count: Millions of species have been identified, but estimates suggest there are many more species yet to be discovered. Biodiversity is currently at its highest point in Earth's history, as inferred from fossil records. Fossil evidence: Fossils show that biodiversity has increased over time, but species extinction events have periodically reduced the number of species (e.g., mass extinctions). Unknown species: Many species, especially in biodiverse regions like tropical rainforests and deep oceans, remain undiscovered. Example: Insects and microorganisms in rainforests and marine environments are still largely undocumented. What are the causes of the current biodiversity crisis? A4.2.6—Causes of the current biodiversity crisis. Include human population growth as an overarching cause, together with these specific causes: hunting and other forms of over-exploitation; urbanisation; deforestation and clearance of land for agriculture with consequent loss of natural habitat; pollution and spread of pests, diseases and invasive alien species due to global transport. Hunting Urbanisation Deforestation Pollution Invasive species 45  Overarching cause: Human population growth leads to increased demand for resources. Specific causes: ○ Hunting and over-exploitation: Overfishing, poaching, unsustainable agriculture. ○ Urbanisation: Expansion of cities reduces natural habitats. ○ Deforestation: Clearing forests for agriculture and infrastructure leads to habitat loss. ○ Pollution: Chemical, plastic, and air pollution degrade ecosystems. ○ Invasive species: Human activities introduce invasive species that outcompete natives. Example: Cane toads in Australia (introduced to eliminate crop pests) and Lantana camara in Southeast Asia (introduced to prevent soil erosion and for aesthetics). Anthropogenic Mass Extinction A4.2.3—Causes of anthropogenic species extinction. This should be a study of the causes of the current sixth mass extinction, rather than of non-anthropogenic causes of previous mass extinctions. To give a range of causes, carry out three or more brief case studies of species extinction: North Island giant moas (Dinornis novaezealandiae) as an example of the loss of terrestrial megafauna, Caribbean monk seals (Neomonachus tropicalis) as an example of the loss of a marine species, and one other species that has gone extinct from an area that is familiar to students. Anthropogenic causes of extinction (current sixth mass extinction): Habitat destruction (deforestation, urbanisation) Overhunting and overfishing Pollution (chemical pollution, plastic waste) Climate change (global warming, ocean acidification) Invasive species (species introduced by humans) 46 Examples of extinction (terrestrial and marine). See case studies from ACTIVITIES North Island Giant Moa (Dinornis novaezealandiae): Date of Extinction: Circa 1400 Cause of extinction: Overhunting by humans. Caribbean Monk Seal (Neomonachus tropicalis): Date of Extinction: Declared extinct in 2008 Cause of extinction: Overhunting for oil and habitat destruction. Passenger Pigeon (Ectopistes migratorius): Date of Extinction: Officially considered extinct in 1914. Cause of extinction: Overhunting and habitat destruction in North America. 47 Causes of ecosystem loss A4.2.4—Causes of ecosystem loss. Should study only causes that are directly or indirectly anthropogenic. Include two case studies of ecosystem loss. One should be the loss of mixed dipterocarp forest in Southeast Asia, and the other should, if possible, be of a lost ecosystem from an area that is familiar to students. Mixed Dipterocarp forests in SE Asia: Direct Anthropogenic Causes: Deforestation for agriculture and logging Urbanisation and infrastructure development Pollution from industry and agriculture Indirect Anthropogenic Causes: Climate change leading to altered weather patterns Invasive species introduction by human activities 48 In the space below provide evidence of direct and indirect anthropogenic causes on an ecosystem that you have recently studied OR use the example of the Dodo or the Tasmanian Tiger found in Kognity. (Link below). Make sure that you provide named examples of each cause. https://app.kognity.com/study/app/ibdp-biology-slhl-2025-pc/sid-422-cid-242422/book/causes-of-anthro pogenic-species-extinction-id-44389/ Named Example:__________________________________ 49 Where’s the evidence? A4.2.5—Evidence for a biodiversity crisis. Evidence can be drawn from Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services reports and other sources. Results from reliable surveys of biodiversity in a wide range of habitats around the world are required. Students should understand that surveys need to be repeated to provide evidence of change in species richness and evenness. Note that there are opportunities for contributions from both expert scientists and citizen scientists. https://app.kognity.com/study/app/ibdp-biology-slhl-2025-pc/sid-422-cid-242422/book/evidence-and-ca uses-of-the-biodiversity-crisis-id-44391/ Why take biodiversity surveys? Provide valuable information to decision-makers regarding the use of resources and species conservation. Take place within a defined area and are repeated to get a better understanding of the biodiversity. Repeated surveys give information about species richness and evenness, helping experts understand changes taking place within a community Biodiversity crisis: Rapid decline in species numbers, driven by human activities. Why is it important to collect evidence from multiple and ongoing surveys? Repeated biodiversity surveys measure changes in species richness (number of species) and evenness (relative abundance). Data is collected globally in ecosystems like forests, oceans, and grasslands. Globally recognised surveys include: Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES): Global assessment report on biodiversity and ecosystem services of the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services | Knowledge for policy Provides scientific reports showing the decline of biodiversity globally. IUCN Red List Red List of Ecosystems Conservation tools to assess current status and inform conservation action and policy. The IUCN Red List of Ecosystems shows the status of thousands of species. Citizen Science: Public participation in biodiversity surveys helps expand the data pool but requires careful consideration of methodology. 50 Task: Use the Kognity link to investigate how public participation (Citizen Science) helps with ‘The Horseshoe Count’ then answer the questions below https://app.kognity.com/study/app/ibdp-biology-slhl-2025-pc/sid-422-cid-242422/book/evidence-and-ca uses-of-the-biodiversity-crisis-id-44391/ 1. When does it happen? 2. Where does it happen? 3. How long have horseshoe crabs migrated like this? 4. Why is the crab spawn (eggs) important to the local ecosystem? 5. How have humans exploited the horseshoe crabs? 6. Why is it important to take the census to understand the number of crabs? 7. Volunteer citizens have to be specially trained to carry out these surveys. What are they trained to look for? Conservation of Biodiversity (Different conservation programmes) A4.2.7—Need for several approaches to conservation of biodiversity. No single approach by itself is sufficient, and different species require different measures. Include in situ conservation of species in natural habitats, management of nature reserves, rewilding and reclamation of degraded ecosystems, ex situ conservation in zoos and botanic gardens and storage of germplasm in seed or tissue banks. https://app.kognity.com/study/app/ibdp-biology-slhl-2025-pc/sid-422-cid-242422/book/8-conservation-o f-biodiversity-id-44392/ Multiple approaches are required to effectively conserve biodiversity, as no single method is sufficient on its own. Different species and ecosystems have unique needs, which require a vari