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. Definitions: - **Ecosystem**: A community of interacting organisms and their physical environment. - **Producers**: Organisms, like plants, that produce their own food through photosynthesis. - **Consumers**: Organisms that gain energy by eating other organisms. - **Energy Flow**: The movement of energy through a food chain or web from producers to consumers. **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. Definitions: - **Population**: A group of individuals of the same species living in an area. - **Community**: A group of populations of different species living together. - **Predator-prey relationship**: An interaction where one organism (the predator) hunts another (the prey). - **Symbiosis**: A close and often long-term interaction between two different species. **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. Definitions: - **Photosynthesis**: The process by which plants use sunlight to make food. - **Herbivores**: Animals that eat plants. - **Carnivores**: Animals that eat other animals. - **Omnivores**: Animals that eat both plants and animals. - **Decomposers**: Organisms that break down dead material, recycling nutrients back into the ecosystem. **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. Definitions: - **Abiotic factors**: Non-living environmental factors like climate and soil. - **Biotic factors**: Living environmental factors, such as plants, animals, and bacteria. - **Population dynamics**: The study of changes in population sizes and their causes. - **Quadrats**: Square sampling plots used in ecological studies to estimate population sizes. **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. Definitions: - **Introduced species**: Species brought by humans to new environments where they are not native. - **Biological control**: The use of natural predators or diseases to manage pest populations. - **Indicator species**: Species whose health reflects the quality of the environment, often used to monitor ecosystem health. **6.6** Ecosystems can support only a certain number of organisms, known as carrying capacity. When populations exceed this, resources become limited, and the population stabilizes. Natural events like floods, droughts, and volcanic eruptions disrupt ecosystems. Floods can bring pollutants, while droughts cause resource shortages and migration. Seasonal changes also affect ecosystems as animals migrate, and plants grow or reproduce, causing population shifts. Human activities, like deforestation, urban sprawl, and agriculture, disrupt habitats, reduce biodiversity, and cause land degradation, impacting soil and ecosystem health. Climate change from human activities alters weather patterns, affecting species\' habitats. Definitions: - **Carrying capacity**: The maximum population size an ecosystem can sustainably support. - **Natural disaster**: An environmental event, such as a flood or wildfire, that disrupts ecosystems. - **Biodiversity**: The variety of life forms within an ecosystem. - **Climate change**: Long-term changes in temperature and weather patterns, often caused by human activities. **5.1** Classification systems help scientists organize and communicate information about living things. Common names can be confusing (e.g., American vs. Australian magpies), so scientists use scientific names, such as *Cracticus tibicen* for the Australian magpie. Early humans classified plants based on their uses, and over time, systems became structured, with scientists like Aristotle and Linnaeus refining methods. Linnaeus developed a system using two-word Latin names to identify organisms by genus and species. Definitions: - **Classification**: The process of organizing living things into groups based on similarities. - **Scientific name**: A standardized Latin name for each species. - **Genus**: The group to which a species belongs, ranked above species in classification. **5.2** Living things share eight characteristics, summarized by MR N GREWW: 1. Movement 2. Reproduction 3. Nutrition 4. Growth 5. Response to stimuli 6. Exchange of gases 7. Waste production 8. Water requirement Definitions: - **Stimuli**: Changes in the environment that organisms respond to. - **Exchange of gases**: The process of taking in oxygen and releasing carbon dioxide (or vice versa, in plants). **5.3** Classification keys are tools that help scientists identify organisms by choosing between two options at each step, leading to the correct classification. **Dichotomous keys** are commonly used, while **tabular keys** are simpler, with choices listed in a table. By answering yes/no questions about traits (e.g., Does it have fur?), scientists can identify organisms. Definitions: - **Dichotomous key**: A classification tool that presents two choices at each step. - **Tabular key**: A simpler key format with two choices per row. **5.4** Linnaean taxonomy organizes organisms into hierarchical groups: Kingdom, Phylum, Class, Order, Family, Genus, and Species. Scientific names use **binomial nomenclature**, combining genus and species (e.g., *Felis catus* for cats). This system has evolved, adding domains like **Eukaryota**, **Bacteria**, and **Archaea** based on genetic differences. Definitions: - **Binomial nomenclature**: The two-part naming system using genus and species. - **Domain**: The highest level in modern classification, above kingdoms. **5.5** Kingdoms in taxonomy classify organisms based on cell features: 1. **Plantae**: Multicellular, autotrophic plants with cell walls. 2. **Animalia**: Multicellular, heterotrophic animals without cell walls. 3. **Fungi**: Feed on decaying matter and have cell walls. 4. **Monera**: Unicellular organisms like bacteria, with cell walls but no nucleus. 5. **Protista**: Mostly unicellular organisms with a nucleus, like amoebas. Definitions: - **Autotrophic**: Organisms that make their own food (e.g., plants). - **Heterotrophic**: Organisms that consume other organisms for energy. **5.6** Invertebrates, animals without a backbone, make up 96% of all animal species and are divided into six main phyla based on body structure, such as spongy bodies in **Poriferans** or segmented bodies in **Arthropods**. Vertebrates are animals with a backbone, including mammals, reptiles, birds, amphibians, and fish, each classified by unique traits like scales, fur, or feather types. Definitions: - **Invertebrates**: Animals without a backbone. - **Vertebrates**: Animals with a backbone. **5.7**\ Vertebrates are animals with a spine or backbone and are divided into five classes based on characteristics like body covering, how they reproduce, 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 include 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. - Ectothermic, meaning their body temperature depends on the environment. 3. **Aves (Birds)**: - Endothermic (maintain a constant body temperature) with feathers and scaly legs. - Lay eggs with hard shells. 4. **Amphibia (Amphibians)**: - Ectothermic 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. - Divided into cartilaginous fish (e.g., sharks, rays) and bony fish (other fish species). Definitions: - **Endothermic**: Organisms that can regulate and maintain a constant internal body temperature, regardless of the external environment (e.g., mammals and birds). - **Ectothermic**: Organisms whose body temperature depends on the surrounding environment (e.g., reptiles, fish). - **Monotremes**: Egg-laying mammals (e.g., platypus). - **Marsupials**: Mammals whose young develop in a pouch (e.g., kangaroos). - **Placentals**: Mammals whose young develop inside the mother\'s body, connected by a placenta.