Ecosystems

Living things are organized into levels: cells form tissues, tissues form organs, organs form organ systems, and organ systems make up a complete organism.

Symbiosis is a close relationship between two different species. In mutualism, both benefit; in parasitism, one benefits while the other is harmed; in commensalism, one benefits and the other is unaffected.

Biomes are large regions with similar climate, plants, and animals. Major biomes include tropical rainforest, desert, grassland, tundra, and temperate forest.

Animal behaviors can be innate (born with) or learned. A spider spinning a web is innate behavior, while a dog learning to sit on command is learned behavior.

Photosynthesis converts light energy into chemical energy stored in glucose. Plants use carbon dioxide from the air and water from the soil, releasing oxygen as a byproduct.

Coral reefs are underwater ecosystems built by tiny coral animals. They support an incredible diversity of marine life including fish, sea turtles, and invertebrates.

Endangered species are at risk of extinction due to habitat loss, pollution, hunting, or climate change. Conservation efforts work to protect these species and their habitats.

Succession is the gradual change of an ecosystem over time. Primary succession begins on bare rock, while secondary succession occurs after a disturbance like a fire.

Animals communicate using sounds, body language, colors, and chemical signals called pheromones. Communication helps them find mates, warn of danger, and mark territory.

Wetlands like marshes and swamps filter water, prevent flooding, and provide habitat for many species. They are among the most productive ecosystems on Earth.