All Organisms are Related through their Evolutionary History

##Evolutionary History of Organisms

  • Every species shares a common ancestor from billions of years ago. Biological diversity that exists today is a result of species being naturally selected over many generations.

  • The study of this evolutionary history is called phylogenetics. Phylogenetics studies the lineages of species and their relationships using molecular sequencing data and morphology.

  • The mapping of these relationships is shown in a phylogenetic tree where each branch point represents a common ancestor.

##Evidence for Evolutionary History

  • The concept of evolution is supported by various sources of evidence including fossil records, comparative anatomy, molecular evidence and biogeography.

  • Fossil Records: This involves studying the remains of ancient organisms buried deep in the earth’s crust. Fossils provide direct evidence of extinct organisms and allow us to see a gradual change and complexity in the structure of organisms over time.

  • Comparative Anatomy: This involves comparing the bodily structures of different organisms. These comparisons can show similarities that suggest a common ancestor. There are two types of structures - homologous structures (same structure, different function - show common ancestry) and analogous structures (different structure, similar function – show adaptation to similar environment).

  • Molecular Evidence: Similarities in DNA and protein structures between different organisms demonstrate shared ancestry. The more similar these structures, the more closely related the organisms are.

  • Biogeography: This is the study of geographical distribution of species. Closely related species tend to be found in the same geographic area because they descended from a local common ancestor. This distribution pattern serves as a testament to evolution.

##Mechanisms of Evolution

  • Natural selection is the process where organisms that are more adapted to their environment survive and pass on their genes. This is a major driving force of evolution.

  • Mutation introduces new genetic variability. This genetic variation may be beneficial, harmful, or neutral. If it enhances survival and reproduction, it will increase in frequency in the population over generations.

  • Other mechanisms such as genetic drift (random chance), gene flow (migration), and non-random mating also contribute to evolutionary changes.

##Evolutionary Relationships and Classification

  • Biologists classify organisms into a hierarchy of taxa: Domain, Kingdom, Phylum, Class, Order, Family, Genus, and Species. This hierarchical system reflects evolutionary relationships between organisms.

  • The classification system has evolved with scientific understanding. Recent developments in molecular biology have led to the new domain system, dividing life into three domains: Bacteria, Archaea, and Eukarya.

  • Species are the most precise level of classification. They are defined as groups of interbreeding natural populations that are reproductively isolated from other such groups. However, defining species can be complex especially in asexual organisms, fossils, and organisms which we’ve only DNA data.

Remember, the more you know about the evolutionary history of life, the deeper your understanding of biodiversity and body physiology. Each organism carries with it a long evolutionary history which has shaped its physiology, behaviour and relationships with other species.