Heridity
Information which is responsible for the phenes of an organism is mostly hereditary. But, environmental factors do significantly influence the expression of this hereditary information.
Information type
There are protein-coding regions, non protein coding RNA regions, regulatory sequences, introns, and noncoding DNA.
Chemical encoding, expression
The most basic stage of expression of hereditary information is its chemical encoding. This happens in either the language of the DNA or the RNA.
Genes
Information-segments encoded in the form of a DNA are sometimes copied into an RNA sequence, which are sometimes inturn copied into amino-acid sequences (proteins).
Protein-coding genes are arguably the most important part of the hereditary information - because changes here can easily lead to markedly varied phenes.
Genome, genotype
The set of all genes in an organism, or a species is a genome. A genotype is a form of a particular gene which distinguishes an individual.
Gene expression
This is affected by many environmental factors (Epigenetics).
Variation
Types
Types of variations include point mutations, recombinations, insertions, deletions in copy stored using the DNA.
Source
These variations could be the result of copying errors during reproduction, intermixing of DNA during reproduction, damage to DNA due to radiation or chemicals, gene insertions/ transfers via viruses.
Variation
The genes and phenes of organisms vary. These variations arise due to environmental processes such as radiation, chemicals, infection etc..
Homology
Homologous genes/ phenes are similar genes/ phenes occurring in different species. If the homology arose due to a speciation event, it is called orthology.