The levels in order from simplest (1) to most complex (6) are;
1. Organism
2. Population
3. Community
4. Ecosystem
5. Biome
6. Biosphere
An organism is a discrete and complete living thing such as animal, plant, fungus or microorganism that is made up of mutually interdependent parts that regulate various important processes.
Population is the collection of organisms of a particular species, living in a given geographical area, sharing particular characteristics of interest and have the ability to interbreed. A population can be influenced by many factors such as mortality, births and migration of organisms.
A community is a group of interdependent organisms inhabiting the same region and interacting with each other.