Ecology

What are the main components of an ecosystem, and how do they interact? How does energy flow from the sun through producers, consumers, and decomposers? Why is only a fraction of energy passed on from one trophic level to the next? How do nutrient cycles like carbon and nitrogen connect living things to the atmosphere and soil? What happens to an ecosystem when a top predator is removed or added?

What factors determine how large a population of a species can become in a given habitat? How do competition, predation, and mutualism shape the structure of a community? What is carrying capacity, and what happens when a population overshoots it? How do ecologists measure and model population growth in the real world? Why do some species become invasive when introduced to new environments?

What are the major terrestrial and aquatic biomes, and how are they defined? How do climate and geography shape the types of organisms that live in each biome? What makes tropical rainforests so biologically diverse compared with other biomes? How are polar and high-altitude ecosystems different from temperate ones? How is climate change expected to alter major biomes over the coming decades?

What is ecological succession, and how does a bare area gradually become a complex ecosystem? How do primary and secondary succession differ from each other? What role do disturbances like fires, storms, or floods play in maintaining biodiversity? How do some species depend on periodic disturbance to complete their life cycles? What happens when human activities change the natural disturbance patterns in an ecosystem?

What are the main ways humans are altering ecosystems on land and in the oceans? How do habitat destruction, pollution, and overexploitation threaten species with extinction? What is biodiversity, and why does its loss matter for human societies? What strategies do conservation biologists use to protect endangered species and habitats? How can individual choices and public policies reduce human impact on ecosystems?