1. Introduction

The gene theory is one of the basic principles of biology.

Genes are located on chromosomes and consist of DNA.

They are the primary unit of heredity and correspond to a region of the DNA which influences the form or function of an organism in specific ways. The result of such influence is called the phenotype (=Erscheinungsbild). The complete assembly of genetic information is called the genotype.

The genotype is the genetic makeup of an organism, while the phenotype is the observable traits resulting from that genetic makeup and the environment.

Examples phenotype: visible traits like Eyecolor, Haircolor, Height

The theory states that cells are the fundamental unit of life and that all living things (except viruses) are composed of one or more cells.

Generally accepted parts of the theory are:

• The cell is the most basic unit of life

• All living organisms are composed of one (unicellular) oder more cells (multicellular)

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

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

• There is energy flow within cells (metabolism, biochemistry)

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

The theory of evolution by natural selection is a central organizing concept of biology. It states that:

• Life changes and develops through evolution

• All life forms known have a common origin

The theory was proposed by Charles Darwin and explains that species change over time because individuals with advantageous traits are more likely to survive and reproduce, passing those beneficial characteristics to their offspring.

The ability of an organism to regulate it’s internal environment to maintain a stable condition despite external changes, allowing for optimal functioning and survival.

Key Principles:

• Self-Regulation

• Dynamic Equilibrium: not a static state but a constant process of adjustment to maintain balance