Answer:
Ecologists often work at five broad levels, sometimes discretely and sometimes with overlap: organism, population, community, ecosystem, and biosphere.
Organisms make up a population. Multiple populations of different species make up a community. Communities in a particular area make up an ecosystem. All of the ecosystems on Earth make up the biosphere.
From smallest to largest:
Organism: Organismal ecologists study adaptations, beneficial features arising by natural selection, that allow organisms to live in specific habitats. These adaptations can be morphological, physiological, or behavioral.
Population: A population is a group of organisms of the same species that live in the same area at the same time. Population ecologists study the size, density, and structure of populations and how they change over time.
Community: A biological community consists of all the populations of different species that live in a given area. Community ecologists focus on interactions between populations and how these interactions shape the community.
Ecosystem: An ecosystem consists of all the biotic and abiotic factors that influence that community. Ecosystem ecologists often focus on flow of energy and recycling of nutrients.
Biosphere: The biosphere is planet Earth, viewed as an ecological system. Ecologists working at the biosphere level may study global patterns—for example, climate or species distribution—interactions among ecosystems, and phenomena that affect the entire globe, such as climate change.
