Sem 2 Exam Notes PDF

**[Scientific Method -- Ch 1]** - **Experimental Accuracy, Reliability, and Validity** - **Accuracy** refers to how close the experimental results are to the true or accepted value. For example, if you\'re measuring the temperature of water and your thermometer is correctly...

**[Scientific Method -- Ch 1]** - **Experimental Accuracy, Reliability, and Validity** - **Accuracy** refers to how close the experimental results are to the true or accepted value. For example, if you\'re measuring the temperature of water and your thermometer is correctly calibrated, you are obtaining accurate data. - **Reliability** refers to the consistency of results when an experiment is repeated. If you repeat your experiment and get similar results each time, your experiment is reliable. - **Validity** means that the experiment is measuring what it is supposed to measure. It's important to control all other variables (controlled variables) to ensure that the results are truly a result of the manipulation of the independent variable. - **Example**: If you test how temperature affects plant growth, ensure factors like light and water are consistent to measure only the effect of temperature. - **Hypothesis and Variables** - **Hypothesis**: A **hypothesis** is a testable prediction of what you expect to happen in your experiment. It often follows an \"If\... then\...\" format. - Example: \"If the temperature increases, then the rate of photosynthesis in plants will increase.\" - **Independent Variable**: The variable you change or manipulate in an experiment. - Example: Temperature in the plant growth experiment. - **Dependent Variable**: The variable you measure in response to changes in the independent variable. - Example: The rate of photosynthesis in the plant growth experiment. - **Controlled Variables**: These are variables you keep constant to ensure that any changes in the dependent variable are due to the independent variable alone. - Example: Light levels, type of plant, soil quality. **[Biodiversity and Classification -- Ch 2]** - **Biodiversity**: - **Genetic Diversity**: Variability in the genetic makeup within a species or population. - Example: Different alleles (versions of genes) for the same trait in a population. - **Species Diversity**: The variety of species within a specific habitat or region. - Example: The Great Barrier Reef has thousands of different species of fish, corals, and other marine life. - **Ecosystem Diversity**: The variety of ecosystems within a geographical location. - Example: Forests, wetlands, deserts, and coral reefs in Australia represent different ecosystems. - **Taxonomic Levels** (from broadest to most specific): - **Domain** \> **Kingdom** \> **Phylum** \> **Class** \> **Order** \> **Family** \> **Genus** \> **Species** - Example: The scientific name of humans is **Homo sapiens**, where **Homo** is the genus and **sapiens** is the species. - **Binomial Nomenclature**: A system of naming organisms by two parts: the genus (capitalized) and the species (lowercase). - Example: **Homo sapiens** for humans, **Panthera leo** for lions. - **Phylogenetic Trees/Cladograms**: Diagrams used to represent evolutionary relationships between species. They show how species are related through common ancestors. - A **cladogram** has branches that represent the evolutionary paths taken by species. - Example: A cladogram may show the relationship between humans, apes, and monkeys, where all share a common ancestor. phylogenetic tree: vertebrates - Students \| Britannica Kids \| Homework Help **[Chapter 3: Ecosystems and Interactions]** - **Ecosystem**: An ecosystem consists of all living organisms (biotic factors) and non-living elements (abiotic factors) that interact in a specific environment. - **Examples of ecosystems**: Rainforests, coral reefs, deserts, and grasslands. - **Biotic and Abiotic Factors**: - **Biotic factors**: The living components of an ecosystem (e.g., plants, animals, bacteria). - **Abiotic factors**: The non-living physical and chemical elements in an ecosystem (e.g., water, sunlight, temperature, soil). - **Ecological Niche**: The role and position a species has in its environment, including all of its interactions with biotic and abiotic factors. - Example: Bees pollinate flowers, which is a specific niche within their ecosystem. - **Food Chains and Food Webs**: - **Food Chain**: A linear sequence showing the flow of energy from one organism to the next, starting with a producer. - **Food Web**: A complex network of interconnected food chains within an ecosystem.  - **Trophic Levels**: Levels of energy transfer in a food chain, including producers (plants), primary consumers (herbivores), secondary consumers (carnivores), and tertiary consumers (top predators). Ecological pyramid - Wikipedia - **Energy Flow and the 10% Rule**: Only about 10% of energy is passed on to each successive trophic level; the rest is lost as heat. - Example: If a plant produces 100 units of energy, only 10 units will pass to the primary consumer. - **Symbiotic Relationships**: - **Mutualism**: Both species benefit (e.g., bees and flowers). - **Commensalism**: One species benefits, and the other is unaffected (e.g., barnacles on a whale). - **Parasitism**: One species benefits at the expense of the other (e.g., fleas on dogs). **[Chapter 4: Population Dynamics]** - **Population**: A group of individuals of the same species that live in the same area and interact. - **Population Size**: The number of individuals within a population. - **Carrying Capacity**: The maximum population size that an environment can sustainably support given its resources. - If a population exceeds its carrying capacity, resources become scarce, potentially leading to a population decrease. - **Population Growth Models**: - **Exponential Growth**: Rapid increase in population size when resources are abundant, producing a J-shaped curve. - **Logistic Growth**: Population growth that stabilizes at the carrying capacity, producing an S-shaped curve. - **Density-Dependent and Density-Independent Factors**: - **Density-Dependent Factors**: Factors that impact population size more as population density increases (e.g., competition, disease). - **Density-Independent Factors**: Factors that impact population size regardless of density (e.g., natural disasters, temperature). - **Sampling Methods for Population Estimation**: - **Quadrat Sampling**: A square plot used to estimate population density of immobile organisms. - **Mark and Recapture**: A method used to estimate population size in mobile organisms by marking a sample, releasing them, and recapturing a second sample. **[Chapter 5: Ecosystem Change]** - **Succession**: - **Primary Succession**: Occurs in an area where no soil exists, starting from bare rock (e.g., following a volcanic eruption). Pioneer species like lichens and mosses break down rocks, gradually creating soil. - **Secondary Succession**: Occurs in areas where an ecosystem previously existed but was disturbed, leaving soil intact (e.g., after a forest fire).  - **Climax Community**: The stable, final stage of succession where the ecosystem remains relatively unchanged until disturbed. - **Disturbances and Ecosystem Resilience**: - **Natural Disturbances**: Events like fires, storms, and floods that can disrupt ecosystems. - **Human Impacts**: Activities like deforestation, pollution, and urban development that alter ecosystems and biodiversity. - **Resilience**: An ecosystem's ability to recover after a disturbance. - **Invasive Species**: Non-native species that disrupt local ecosystems by outcompeting native species for resources. - Example: Cane toads in Australia are invasive and have disrupted local species. - **Biodiversity Hotspots**: Regions with high levels of biodiversity that are under threat from human activities. - Examples: The Amazon rainforest and the Great Barrier Reef. - **Nitrogen Cycle** - **Definition**: The process by which nitrogen moves through the atmosphere, soil, water, and living organisms in different chemical forms. - **Key Processes**: 1. **Nitrogen Fixation**: - Conversion of atmospheric nitrogen (N₂) into ammonia (NH₃) or nitrate (NO₃⁻). - Performed by nitrogen-fixing bacteria (e.g., *Rhizobium* in legume roots) or by lightning. 2. **Nitrification**: - Ammonia (NH₃) is converted to nitrite (NO₂⁻) and then nitrate (NO₃⁻) by nitrifying bacteria (*Nitrosomonas* and *Nitrobacter*). 3. **Assimilation**: - Plants absorb nitrate (NO₃⁻) or ammonia (NH₃) and incorporate it into organic compounds (e.g., proteins). 4. **Ammonification**: - Decomposers convert organic nitrogen in dead organisms/waste back into ammonia (NH₃). 5. **Denitrification**: - Denitrifying bacteria convert nitrate (NO₃⁻) back into nitrogen gas (N₂), releasing it into the atmosphere. - **Importance**: 1. Essential for plant growth and protein synthesis in organisms. 2. Nitrogen is a critical component of DNA, RNA, and proteins. Nitrogen Cycle - Definition and Stages \| GeeksforGeeks - **Phosphorus Cycle** - **Definition**: The process by which phosphorus moves through rocks, soil, water, and living organisms, with no gaseous phase. - **Key Processes**: 1. **Weathering**: - Phosphate ions (PO₄³⁻) are released from rocks through weathering into soil and water. 2. **Absorption by Plants**: - Plants absorb phosphate from the soil and incorporate it into organic compounds (e.g., ATP, DNA). 3. **Consumption**: - Animals consume plants and use phosphorus for bones, teeth, and cellular functions. 4. **Decomposition**: - Decomposers return organic phosphorus from dead organisms/waste back to soil as phosphate. 5. **Sedimentation**: - Phosphates in water bodies settle into sediments, forming rocks over geological time. - **Importance**: 1. Critical for energy transfer (ATP), genetic material (DNA/RNA), and bone development.  **[Chapter 6: Cells and Their Environment]** - **Homeostasis**: The maintenance of a stable internal environment in an organism despite changes in external conditions. - Example: Human body temperature regulation. - **Diffusion and Osmosis**: - **Diffusion**: The movement of particles from an area of higher concentration to an area of lower concentration. - **Osmosis**: The movement of water across a semi-permeable membrane from an area of low solute concentration to an area of high solute concentration. Main Difference Between Osmosis and Diffusion in Biology \| YourDictionary - **Hypertonic, Hypotonic, and Isotonic Solutions**: - **Hypertonic Solution**: Has a higher solute concentration than the cell, causing water to move out and the cell to shrink. - **Hypotonic Solution**: Has a lower solute concentration than the cell, causing water to move in and the cell to swell. - **Isotonic Solution**: Has an equal solute concentration, so there is no net movement of water and the cell maintains its shape.  - **Endocytosis and Exocytosis**: - **Endocytosis**: The process of taking in large molecules by engulfing them in a vesicle. - Example: White blood cells use endocytosis to engulf pathogens. Endocytosis and Exocytosis: Differences and Similarities \| Technology Networks - **Exocytosis**: The process of expelling large molecules by merging vesicles with the cell membrane. - Example: Nerve cells use exocytosis to release neurotransmitters.  **[Chapter 7: Cellular Respiration and Energy Transformation]** - **ATP (Adenosine Triphosphate)**: The primary energy carrier in cells. - ATP releases energy when its high-energy phosphate bonds are broken, converting it to ADP (Adenosine Diphosphate). - **Cellular Respiration**: The process by which cells produce ATP by breaking down glucose and other molecules. - **Aerobic Respiration** (requires oxygen): Produces a large amount of ATP. - Equation: C6H12O6+6O2→6CO2+6H2O+Energy (ATP) - Occurs in three stages: - **Glycolysis**: Occurs in the cytoplasm, breaking down glucose into pyruvate. - **Krebs Cycle** (Citric Acid Cycle): Occurs in the mitochondria, producing electron carriers. - **Electron Transport Chain**: Occurs in the inner mitochondrial membrane, where most ATP is produced. - **Anaerobic Respiration** (without oxygen): Produces less ATP and results in lactic acid or ethanol as byproducts. - **In animals**: Produces lactic acid and a small amount of ATP. - Equation: Glucose → Lactic Acid + Energy (ATP) - **In plants and yeast**: Produces ethanol and carbon dioxide (fermentation). - Equation: Glucose→Ethanol+CO2+Energy (ATP) - **Photosynthesis vs. Cellular Respiration**: - **Photosynthesis** stores energy in glucose, while **cellular respiration** releases energy from glucose. - **Photosynthesis Equation**: 6CO2+6H2O+light energy→C6H12O6+6O2​ - **Organelles Involved**: - **Mitochondria**: Where cellular respiration occurs. - **Chloroplasts**: Where photosynthesis occurs in plant cells. **[Cells -- Ch 8]** - **Cell Organelles and Functions** - **Nucleus**: Contains the cell's genetic material (DNA) and controls cell activities. The \"brain\" of the cell. - **Mitochondria**: The powerhouse of the cell. They produce energy in the form of **ATP** (adenosine triphosphate) through cellular respiration. - **Formula for Cellular Respiration**:\ Glucose + Oxygen → Carbon Dioxide + Water + Energy (ATP) - **Endoplasmic Reticulum (ER)**: There are two types: - **Rough ER**: Studded with ribosomes, synthesizes proteins. - **Smooth ER**: Synthesizes lipids and detoxifies chemicals. - **Golgi Apparatus**: Modifies, sorts, and packages proteins and lipids for transport or secretion from the cell. - Example: After proteins are made in the rough ER, the Golgi body modifies them (e.g., adding sugars) and packages them into vesicles. - **Ribosomes**: Tiny structures where protein synthesis occurs, translating messenger RNA (mRNA) into proteins. - **Lysosomes**: Contain digestive enzymes that break down waste materials and cellular debris. - **Chloroplasts** (in plant cells): Site of photosynthesis, converting solar energy into chemical energy stored in glucose. - **Photosynthesis Equation**: 6CO2+6H2O+light energy→C6H12O6+6O2 ​ Human cell structure diagram medical science Vector Image  **[Membranes and Transport -- Ch 9]** - **Plasma Membrane Components and Function** - **Phospholipid Bilayer**: A double layer of lipids with hydrophilic (water-attracting) heads and hydrophobic (water-repelling) tails. It acts as a barrier. - **Proteins**: - **Channel Proteins**: Allow the passage of ions or molecules across the membrane. - **Carrier Proteins**: Bind to specific molecules and change shape to transport them across the membrane. - **Receptor Proteins**: Receive chemical signals, initiating a response in the cell. - **Passive and Active Transport** - **Passive Transport**: Movement of substances across the membrane without energy expenditure, down the concentration gradient. - **Diffusion**: Movement of small molecules like oxygen and carbon dioxide through the lipid bilayer. - **Osmosis**: Movement of water through a semi-permeable membrane. - **Active Transport**: Movement of substances against the concentration gradient, requiring energy (ATP). - Example: The **sodium-potassium pump** moves sodium ions out and potassium ions into the cell.  - **Endocytosis and Exocytosis**: Processes by which cells ingest or expel materials in vesicles. - Example: White blood cells use **phagocytosis** (a type of endocytosis) to engulf bacteria. - **Surface Area to Volume Ratio**: Cells need a large surface area relative to their volume to maximize the exchange of materials across the membrane (e.g., oxygen, nutrients). - **Small cells** have a higher surface area to volume ratio, making diffusion more efficient. **[Enzymes, Photosynthesis and Respiration - Ch 10]** - **Role of Enzymes as Biological Catalysts** - Enzymes speed up biochemical reactions by lowering the **activation energy**, the energy required to start a reaction. - **Lock and Key Model**: The enzyme\'s active site is a perfect fit for the substrate (the molecule it acts on). Enzymes (A-Level) --- the science sauce - **Induced Fit Model**: The enzyme's active site changes shape slightly to accommodate the substrate.  - **Metabolism** - **Catabolism**: Breaking down complex molecules into simpler ones (e.g., cellular respiration). - **Anabolism**: Building complex molecules from simpler ones (e.g., protein synthesis). Coupling of anabolic and catabolic pathways Anabolism utilises energy\... \| Download Scientific Diagram - **Photosynthesis**: - **Light-dependent reactions** occur in the thylakoid membranes of the chloroplast, producing ATP and NADPH. - **Light-independent reactions** (Calvin Cycle) use ATP and NADPH to convert CO2 into glucose. - **Cellular Respiration** - **Glycolysis**: Occurs in the cytoplasm, where glucose is broken down into pyruvate, producing 2 ATP molecules. - **Citric Acid Cycle** (Krebs Cycle): Occurs in the mitochondria, producing ATP and electron carriers. - **Electron Transport Chain**: Uses oxygen to produce large amounts of ATP. **[Animal Systems -- Ch 12]** - **Circulatory Systems**: - **Single Circulatory System**: Found in fish, where blood flows through the heart once per circuit. - **Double Circulatory System**: Found in mammals, where blood flows through the heart twice (pulmonary and systemic circuits).  - **Open Circulatory System:** - **Blood Flow**: Blood (hemolymph) flows freely through body cavities, bathing tissues. - **Pressure**: Low blood pressure. - **Examples**: Insects, spiders, mollusks (e.g., snails). - **Advantages**: Simple, less energy required. - **Disadvantages**: Less efficient nutrient and oxygen transport. - **Closed Circulatory System:** - **Blood Flow**: Blood is confined to blood vessels, pumped by the heart. - **Pressure**: High blood pressure, more efficient. - **Examples**: Mammals, birds, fish, earthworms. - **Advantages**: Efficient transport, controlled blood flow. - **Disadvantages**: More complex, energy-demanding. Circulation - **Gas Exchange Surfaces**: - **Trachea** (insects), **gills** (fish), and **lungs** (humans) are specialized structures for gas exchange. - **Counter-Current Exchange System**: In fish gills, blood flows in the opposite direction to water, maximizing oxygen uptake.  **[Plant Systems -- Ch 13]** - **Vascular Plants**: - **Xylem**: Transports water and minerals upward from the roots to the leaves. - **Phloem**: Transports sugars produced in photosynthesis to other parts of the plant. Flowering plants and the role of phloem and xylem \| What are they? - **Stomata and Guard Cells**: - **Stomata**: Pores on leaves where gas exchange (CO2 in, O2 out) occurs. - **Guard Cells**: Control the opening and closing of stomata to regulate water loss and gas exchange.