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 due to the buildup of greenhouse gases in the atmosphere, primarily from human activities like burning fossil fuels. An example of its effect is the melting of polar ice caps, leading to rising sea levels. 2. Endangered species: An endangered species is a population of organisms at risk of becoming extinct because it is either few in number, or threatened by changing environmental or predation parameters. For instance, the Giant Panda is an endangered species primarily due to habitat loss and fragmentation. 3. Energy flow in an ecosystem: This describes the movement of energy through a food chain or food web, typically starting from the sun and moving through different trophic levels. For example, in a grassland ecosystem, sunlight energy is captured by grass (producer), which is then eaten by a rabbit (primary consumer), and the rabbit is eaten by a fox (secondary consumer). 4. Ozone layer depletion: This is the thinning of the ozone layer in the Earth's stratosphere, which protects life from harmful ultraviolet (UV) radiation from the sun. It is primarily caused by the release of human-made chemicals like chlorofluorocarbons (CFCs). A consequence of depletion is an increased risk of skin cancer and cataracts in humans. What's next?