Genes are the primary units of heredity, it is a region of the DNA that influences the form or function of an organism in a specific way. The result of such influence is called the phenotype (Erscheinungsbild).

The complete assembly of genetic information is call genotype.

The theory states that the cell is the fundamental unit of life, and that all living things (expect viruses) are composed of one or more cells or the secreted product of those cells.

The generally accepted parts of the cell theory include:

• The cell is the fundamental unit of structure and function in all-living organisms

• All cells arise from pre-existing cells by division.

• Energy flows (metabolism and biochemistry) occurs within cells.

• Cells contain hereditary information (DNA) which is passed from cell to cell during cell devision.

• All cells are basically the same in chemical composition in organisms of similar species

• All known living species are made up of one or more cells

• Some organisms are made up of only one cell and are known as unicellular organisms

• Others are multi-cellular, composed of a number of cells

• The activity of an organism depends on the total activity of independent cells

The gene and cell theory but also theory of evolution by natural selection and the theory of homeostasis are all part of the modern biology.

The theory of Evolution by Natural selection:

• all life-forms come from a common origin and life changes and develops through evolution.

The theory of Homeostasis:

• is the ability of an organism to regulate it’s internal environment to maintain a stable condition.

It still is a challenge for scientists and philosophers, it must include all life we are familiar with, but no exclude life forms that might be fundamentally different from life on earth (Aliens).

• A network of regulatory mechanisms (negative feedbacks) inferior to the potential of expansion and reproduction (positive feedback).

• Living things are self organizing and autopoietic (they produce and maintain without help).

• Living beings are thermodynamic systems that have an organized molecular structure.

• Things with the capacity for metabolism and motion.

• Life is a delay of the spontaneous diffusion or dispersion of the internal energy of the biomolecules towards more potential micro states.

• Life is a way to hydrogenate carbon dioxide.

• Life is a self sustained chemical system capable of undergoing Darwinian evolution (NASAs definition).

• Life is matter that cam reproduce itself and evolve as survival dictates.

Life can be seen as a property of an ecological system rather than a single organism on the other hand the Gaia theory states that life, functions as a single organism which maintains the environmental conditions necessary for it’s survival.