Average ppls can give u note abt unit 3only. . . 😌🙌🙌😁

Cell Biology Cell Theory: All living things are made of cells, the basic unit of life, and all cells come from pre-existing cells. Types of Cells: Prokaryotic (no nucleus, simpler structure, e.g., bacteria) and eukaryotic cells (with a nucleus, complex, e.g., plants and animals). Cell Organelles: Key organelles include the nucleus (controls cell functions), mitochondria (energy production), ribosomes (protein synthesis), chloroplasts (photosynthesis in plants), and the cell membrane (controls what enters and exits). Cell Division: Mitosis (growth and repair, two identical cells) and meiosis (produces four cells for reproduction, each with half the chromosomes). --- 2. Genetics and Heredity DNA and Genes: DNA holds genetic information in a double-helix structure; genes are DNA segments that code for traits. Mendelian Genetics: Dominant and recessive traits are passed from parents to offspring. Punnett squares help predict genetic outcomes. Genotype and Phenotype: Genotype is the genetic makeup, while phenotype is the observable trait. --- 3. Evolution and Natural Selection Theory of Evolution: Charles Darwin's theory states that species change over time due to natural selection. Natural Selection: Organisms with favorable traits are more likely to survive and reproduce, passing these traits to the next generation. Adaptation and Evidence: Traits that improve survival (adaptations) become common; evidence includes fossils, anatomy, and genetic similarities. --- 4. Ecology and Ecosystems Ecosystems: Include all living (biotic) and non-living (abiotic) elements in an environment. Energy Flow: Flows from producers (plants) to consumers (animals) and decomposers (fungi and bacteria) in food chains and food webs. Cycles in Nature: Water, carbon, nitrogen, and phosphorus cycles recycle essential elements through ecosystems. Population Dynamics: Factors like carrying capacity and limiting factors affect population growth and interactions. --- 5. Human Biology Body Systems: Major systems include circulatory (transports nutrients), respiratory (gas exchange), digestive (breaks down food), nervous (controls activities), and immune (defends against pathogens). Homeostasis: The body’s ability to maintain a stable internal environment, such as constant temperature and pH.