Biodiversity and Systematics

• Biodiversity – the branch of Biology that investigates the variety of organisms at all levels from populations to ecosystems
• Over the years, the number of identified organisms has increased from thousands to millions
• Every year, new organisms are discovered and species go extinct, so diversity is always changing
• In order to understand biodiversity better, scientists have put together classification systems

• Taxonomy – science of describing, naming and classifying organisms
• There have been several different taxonomic systems throughout history
– 2400 years ago, Aristotle classified organisms as either plants or animals
– Carl Linnaeus then grouped organisms into categories based on form and structure

• Modern biologists have changed the Linnaen system
• In Linnaeus’ system, the largest categories were kingdoms, but we now have domains which are the largest category
• Domains encompass kingdoms, phyla,
classes, orders, families, genera and species’

• When Linnaeus classified organisms, he gave each organism two names: the genus name followed by the species name (always written in
italics or underlined)
• This system is known as binomial nomenclature
• Because the species name is unique, it is often quite descriptive
• There are certain organisms that will have
subspecies – usually for members of a species that live in different areas

• Now that DNA technology has advanced, organisms are being reclassified based on their natural relationships
• Phylogenetics – the analysis of evolutionary history of a species or taxon
• By comparing DNA and RNA of different organisms, we can build phylogenetic trees to show relationships
• These “new” trees can differ substantially from the original due to new information through genetics

• Fossil evidence has given a lot clues as to how organisms are related, but there isn’t a lot of fossil evidence for organisms like worms, fungi and bacteria
• Scientists compare homologous, analogous, and vestigial structures along with embryology and DNA to discover how organisms are related and if they share a recent common ancestor

• Cladistics – a system that uses shared and derived characteristics to created phylogenetic trees
• Shared character – a feature that all members of a group have in common
• Derived character – a feature that evolved only within the group under consideration
• For example: feathers are a derived characteristic of birds

• A clade is a group of organisms that includes an ancestor and all its descendants
• When cladists create phylogenetic diagrams called cladograms
• New cladograms use both anatomical similarities and DNA similarities