Hey Gobte, good to see you again. Here are the explanations for the terms you asked about: 1. Global warming: This refers to the long-term increase in Earth's average surface temperature, primarily due to the enhanced greenhouse effect. This effect is caused by the accumulation of greenhouse gases like carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O) in the atmosphere, largely from human activities such as burning fossil fuels and deforestation. A significant consequence is the melting of glaciers and polar ice caps, leading to rising sea levels and more frequent extreme weather events. 2. Endangered species: An endangered species is a population of organisms that faces a very high risk of extinction in the wild in the near future. This classification is often determined by organizations like the IUCN Red List. Threats include habitat loss and fragmentation, poaching, pollution, climate change, and the introduction of invasive species. For example, the Amur Leopard is critically endangered due to poaching and habitat destruction in its limited range. 3. Energy flow in an ecosystem: This describes the unidirectional transfer of energy from one trophic level to the next within an ecosystem, originating primarily from solar energy. Producers (e.g., plants) convert light energy into chemical energy through photosynthesis. This energy is then transferred to primary consumers (herbivores), then to secondary consumers (carnivores), and so on. A key principle is the 10% rule, where only about 10% of the energy from one trophic level is transferred to the next, with the rest lost as heat during metabolic processes. 4. Ozone layer depletion: This is the thinning of the ozone layer (O₃) in the Earth's stratosphere, which is vital for absorbing harmful ultraviolet (UV) radiation from the sun. The primary cause is the release of human-made chemicals, particularly chlorofluorocarbons (CFCs) and halons, which were once common in refrigerants and aerosols. These chemicals release chlorine and bromine atoms that catalytically destroy ozone molecules. The consequence is an increase in UV radiation reaching the Earth's surface, leading to higher rates of skin cancer, cataracts, and damage to marine phytoplankton. What's next?