Molecule 

Isotopes differ based on anatomic weights and numbers of neutrons in the nucleus. They can be stable and unstable elements. 

Isotopes in Absolute Dating 

The smallest piece of a chemical element or ordinary matter

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

Traditional Biological Organisation Scheme

A substance in its simplest form, meaning that it cannot be broken down further via chemical processes. All matter is composed of these elements. 

Chemical Element

Wikipedia

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

Any living thing that functions as a singular entity

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)

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

Ecosystem

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

Types of Macromolecules

A table showing all the known chemical elements. It is structured around periodic trends, and arranged according to atomic number, electron configuration, and chemical properties.

Modern 18-Column Table:

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