Science Revision Notes PDF

Science Notes  **Watch Video in spire 1.2 Bees ( Key video for exam, Species and Genus)**  A person in front...

Science Notes  **Watch Video in spire 1.2 Bees ( Key video for exam, Species and Genus)**  A person in front of a white board Description automatically generated **6.1** All organisms depend on each other for survival. In ecosystems, *producers* (such as plants) convert sunlight into energy, while *consumers* rely on eating other organisms to gain energy. These relationships are illustrated in food chains and food webs: 1. **Food Chains** show a direct flow of energy from one organism to another. Energy begins with producers and moves up to primary, secondary, and tertiary consumers. 2. **Food Webs** illustrate the interconnectedness of multiple food chains, showing how different organisms rely on a variety of foods for survival. This \"web of life\" highlights the complex interdependence within ecosystems. By understanding food chains and webs, we see how energy flows and nutrients cycle through living things in any ecosystem. **6.2** Ecosystems are communities of living organisms and their environment, where organisms have specific roles and interdependencies. Populations of the same species form communities, and different species interact in various relationships. 1. *Predator-prey*: Predators hunt prey for survival. 2. *Competition*: Species may compete for resources. 3. *Symbiosis*: Includes relationships such as: - **Mutualism**: Both species benefit (e.g., algae and fungi in lichen). - **Commensalism**: One species benefits without affecting the other. - **Parasitism**: One species benefits at the expense of the host. These interactions are essential for ecosystem balance and survival. **6.3** Energy flows through ecosystems as plants capture sunlight through photosynthesis, producing food that herbivores, carnivores, and omnivores rely on. Each step in the food chain shows this energy transfer, represented by arrows pointing from prey to predator. Decomposers, like fungi and bacteria, break down dead organisms, recycling nutrients into the soil, which plants absorb. This cycle maintains balance in ecosystems. Wetlands and forests also filter pollutants from water, supporting ecosystem health. If photosynthesis or decomposers ceased to function, energy and nutrient cycles would collapse, disrupting life across ecosystems. **6.4** In ecosystems, population sizes fluctuate due to **abiotic factors** (non-living aspects like sunlight, water, and temperature) and **biotic factors** (living organisms, including predators, plants, and competition). Populations grow with births and immigration and shrink with deaths and emigration, maintaining a dynamic balance. Ecosystem balance relies on interactions among organisms. For example, if frog numbers drop, grasshopper populations may grow, affecting grass availability and other species in the food web. Population dynamics, the study of these changes, helps scientists predict trends and protect species. To measure populations, scientists use methods like **quadrats** (sampling square plots) for plants and stationary organisms and **capture--recapture** for mobile animals. Modern techniques include remote cameras and audio recordings to monitor populations with minimal disturbance. **6.5**  **Introduced Species** disrupt ecosystems by altering food webs and population balances.  **Examples**: - *Cane Toads* introduced to control beetles harmed native species and disrupted food webs. - *Gamba Grass* suppressed native vegetation, increasing fire risk. - *Macquarie Island Rabbits*: Rabbit populations surged after cat removal, leading to vegetation loss.  **Biological Control** (like the Myxoma virus for rabbits) can initially reduce invasive populations, but species may develop immunity, requiring careful planning to avoid further imbalance.  **Indicator Species**: Amphibians reflect environmental health risks, with many facing extinction, highlighting ecosystem vulnerability. **6.6**  **Carrying Capacity:** - Ecosystems can support only a certain number of organisms. When populations exceed this, resources become limited, and the population stabilizes.  **Natural Disasters:** - Events like floods, droughts, and volcanic eruptions disrupt ecosystems. Floods bring pollutants, while droughts cause resource shortages and migration.  **Seasonal Changes:** - Animals migrate, and plants grow or reproduce, causing population shifts and competition for resources, which maintains balance.  **Human Impacts:** - Deforestation, urban sprawl, and agriculture lead to habitat loss, soil erosion, and reduced biodiversity.  **Land Degradation:** - Clearing land for farming causes soil erosion, reducing ecosystem health.  **Urban Sprawl:** - Cities expand into natural areas, affecting landscapes and resources.  **Climate Change:** - Human activities change weather patterns, impacting ecosystems, like alpine habitats becoming less suitable for some species. 5.1  **Purpose of Classification:** - Classification systems help scientists organize and communicate information about living things.  **Scientific vs. Common Names:** - Common names can be confusing (e.g., American and Australian magpies). Scientific names, like *Cracticus tibicen* for the Australian magpie, are universally understood by scientists.  **Early Classification:** - Early humans classified plants based on their uses (e.g., edible or poisonous). Over time, classification systems became more structured, with scientists like Aristotle and Linnaeus refining methods.  **Linnaean Classification System:** - Carolus Linnaeus simplified classification by using a eight-level system, reducing long Latin descriptions to single-word names for each organism. Domain, Kingdom, Phylum, Order, class, Family, Genus, Speacies.  **Finding New Species:** - New species continue to be discovered. For example, seven new species of peacock spiders were identified in 2020. Discovering and naming new species is crucial, especially for potential medical breakthroughs. **5.2**  **Eight Characteristics of Living Things (MR N GREWW):** - **M**ovement: Living things can move on their own (e.g., animals, plants). - **R**eproduction: Living things reproduce (e.g., animals mate, plants grow from seeds). - **N**utrition: Living things need nutrients to survive (e.g., plants make their own food, animals consume food). - **G**rowth: Living things grow over time (e.g., humans grow from babies to adults). - **R**esponse: Living things respond to stimuli (e.g., animals flee from danger, plants adjust to light). - **E**xchange of gases: Living things exchange gases with their environment (e.g., humans breathe, plants take in carbon dioxide). - **W**aste production: Living things produce waste (e.g., humans excrete, plants release waste through leaves). - **W**ater: Living things need water for survival (e.g., hydration, chemical reactions).  **Living vs. Non-Living vs. Dead:** - **Living:** Exhibits all eight characteristics (e.g., plants, animals). - **Dead:** Was once living but no longer exhibits these characteristics (e.g., dried flower). - **Non-Living:** Never had the characteristics of life (e.g., rocks, robots). **5.3**  **Classification Keys**: - **Key**: A visual tool used to classify organisms. - **Dichotomous Key**: A type of key where each step offers two choices (yes/no) to lead to the identification of an organism. It is called \"dichotomous\" because it splits into two options at each stage. - **Tabular Key**: A type of key presented in a table format that also uses two choices at each step to guide classification, often used in field guides.  **Using Dichotomous Keys**: - These keys help scientists identify organisms by making simple, binary decisions at each step (e.g., Does it have fur? Yes or No?). - As you answer questions, the key directs you to further questions or final identification. - Example: Dr. Redback used a dichotomous key to classify his family members and pets based on characteristics like hair, ears, or whether they could fly.  **Tabular Keys**: - Used when large diagrams are not practical. These keys list two choices at each stage in a table format. - Example: The tabular key for Dr. Redback's family helps to classify each individual based on traits such as whether they can fly, their gender, or hair color.  **Applications**: - **Classifying Organisms**: Dichotomous and tabular keys are essential tools in biology for sorting and identifying species based on specific characteristics. - **Creating Keys**: When developing a key, careful selection of distinguishing characteristics is crucial for accurate classification. **5.4**  **Linnaean Taxonomy:** - Organisms are classified into seven levels: Kingdom, Phylum, Class, Order, Family, Genus, Species. - Example: **Felis catus** (domestic cat) - **Kingdom**: Animalia - **Genus**: Felis - **Species**: catus  **Binomial Nomenclature:** - Scientific names use two parts: genus (capitalized) and species (lowercase), written in italics. - Example: **Felis catus** (domestic cat)  **Evolution of Classification:** - Originally three kingdoms; now five, plus a three-domain system (Eukaryota, Bacteria, Archaea) based on genetic differences. **5.5** Taxonomists classify organisms into kingdoms based on cell features. There are five main kingdoms: 1. **Kingdom Plantae**: Multicellular, autotrophic plants with a cell wall and nucleus. 2. **Kingdom Animalia**: Multicellular, heterotrophic animals without a cell wall, but with a nucleus. 3. **Kingdom Fungi**: Organisms like mushrooms and molds that do not make their own food and feed on decaying matter. They have a nucleus but no cell wall. 4. **Kingdom Monera**: Simple, unicellular organisms (like bacteria) that have a cell wall but no nucleus. 5. **Kingdom Protista**: Mostly unicellular organisms with a nucleus, like amoeba and plankton. **5.6** Invertebrates are animals that either have an external skeleton (exoskeleton) or no skeleton at all. They make up 96% of all animal species. There are six main phyla used to classify invertebrates based on characteristics like body structure and features: 1. **Poriferans**: Spongy bodies with holes, live in water (e.g., sponges). 2. **Cnidarians**: Soft, hollow bodies with tentacles, live in water (e.g., corals, jellyfish). 3. **Arthropods**: Segmented bodies, jointed legs, and an exoskeleton (e.g., insects, spiders). 4. **Molluscs**: Soft bodies, often with a shell (e.g., snails, octopuses). 5. **Echinoderms**: Spiny skin with arms radiating from the center (e.g., sea urchins, starfish). 6. **Nematodes, Platyhelminths, and Annelids**: Soft, long bodies, some segmented or flat (e.g., worms, leeches). **5.7** Vertebrates are animals with a spine or backbone, divided into five classes based on body covering, how their young are born, and body temperature: 1. **Mammalia** (Mammals): - Have hair or fur and can maintain a constant body temperature (endotherms). - Give birth to live young and feed them with milk. - Subgroups: *Monotremes* (lay eggs), *Marsupials* (young develop in a pouch), and *Placentals* (young develop inside the mother). 2. **Reptilia** (Reptiles): - Covered in scales and breathe through lungs. - Ectotherms (body temperature matches the environment). 3. **Aves** (Birds): - Endothermic (constant body temperature) with feathers and scaly legs. - Lay eggs with hard shells. 4. **Amphibia** (Amphibians): - Ectotherms with soft, slimy skin. - Begin life in water with gills, then develop lungs to live on land. 5. **Pisces** (Fish): - Most are ectothermic with scales and fins. - Live in water and breathe with gills. - Grouped into those with cartilage skeletons (sharks, rays) and bony skeletons (other fish).