An ecosystem describes the interactions between groups of organisms from all biological domains and nonliving things in a shared geographical space.

Ecosystem

Cell theory is a scientific theory with three claims:
- all living organisms are made up of one or more cells
- cells are the smallest unit of structure in organisms
- cells are made from other cells

Cell Theory

Symbiosis is any close relationship shared by two biological organisms of different species (called symbionts).

Symbiosis (long term interspecific interactions)

Any living thing that functions as a singular entity

Georgetown University

- Atom
- Molecule
- Macromolecule
- Cell
- Tissue
- Organ
- Organ system
- Organism
- Population
- Community
- Ecosystem
- Biosphere / Ecosphere

Traditional Biological Organisation Scheme

Solomon, Eldra P.; Berg, Linda R.; Martin, Diana W. (2002), Biology (6th ed.), Brooks/Cole, ISBN 0-534-39175-3, LCCN 2001095366

Biology by Solomon, Berg, and Martin

Molecule 

The smallest piece of a chemical element or ordinary matter

Atom

Cell

Tissue

A group of tissues with a similar function

Organ

A group of organs that work together to execute one or more functions.

Organ system

Organism 

A group of organisms that are (1) the same species (2) in a shared geographical area, and (3) able to interbreed

Population (Biology)

Groups of populations of different species that interact with each other.

Community (Biology)

All life on Earth (the sum of all ecosystems on earth)

Biosphere / Ecosphere

There are many types of macromolecules such as: 

- carbohydrates
- lipids
- proteins
- nucleic acids

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