Organizing Life’s Diversity

• Classification – the grouping of objects or information based on similarities.

(ie. organizing your CD collection)

• Taxonomy – the branch of biology that groups and names organisms based on studies of their different characteristics.

• Aristotle developed the first widely accepted system of biological classification

Two groups: Plants and Animals• Carolus Linnaeus developed classification

system based on physical and structural similarities of organisms which is still used today and includes classification based on structural similarities and evolutionary relationships of species.

• Binomial Nomenclature – Two word naming, developed by Linnaeus to identify species– First word = genus – Second word = species

(ie. Homo sapiens = modern humans)

Note: Scientific names are always written in italics or underlined

• Today’s phylogenetic classification uses a hierarchy of taxa to classify organisms.

• From largest to smallest (A mnemonic to help you remember)

Kingdom King

Phylum Phillip Another way to help you

Class Came remember the order, sing the

Order Over groups to the tune of

Family For “Yankee Doodle.”

Genus Green

Species Silk

• The phylogeny for a Bobcat is:

Kingdom Animalia The six kingdoms of organisms are:

Phylum Chordata Eubacteria

Class Mammalia Archaebacteria

Order Carnivora Protists

Family Felidae Fungi

Genus Lynx Plants

SpeicesLynx rufus Animals

Evolutionary History

• Phylogeny describes the evolutionary history of a related group of species

• All organisms on Earth evolved from a single ancestor

• Life on earth began about 3.5 billion years ago; since that time, new species have emerged, lived and died out

• New species evolve from pre-existing species

Fossil Evidence

• Through fossil evidence, physical and molecular similarities between ancient species and modern species have been found.

• Physical and molecular similarities between diverse species has also been found.

• Cladistics – a type of classification system based on phylogeny (evolutionary history)

• Scientists use a cladogram to diagram evolutionary relationships of traits

Phylogeny of Humans

Phylogeny of Humans

Extinction

• Organisms try to survive in their environments through adaptation, however many species become extinct

• Extinction can occur because of environmental changes, human interference or as a result of failure to adapt to new conditions

Extinction Cont.

• Extinction is a natural and important part of evolution

• It is estimated that 999 of every 1,000 species that have ever lived on Earth have become extinct

• The average species survives between 2 and 10 million years

• Even the most highly adapted species become extinct.

Mass Extinctions

• There have been many mass extinctions during Earth’s history

• Mass extinction = when more than 50% of species were wiped out

• Mass extinctions make it possible for new species to develop

• Surviving species are able to diversify