Diversity of Organisms 5 to 30 million species estimated Axolotl.

Diversity of Organisms

• 5 to 30 million species estimatedAxolotl

Organisms alive today descended from earlier species

• Fossils – Remains of previous forms

– Record of life’s history

• Life on Earth – Single cell organisms for

3.5 billion years

– Abundant multicellular life for 500 million years

Evolution

• Change is species over time

• Organisms alive today descended from older organisms

• Evidence is overwhelming

Organization of the Living World

• System to deal with millions of species

• An organism belongs to a unique species

Bird’s nest fungi


• Species designated by a scientific name– Binomial nomenclature – two part name– Developed by Carolus Linnaeus– Example: Homo sapiens

• Homo = genus name

• sapiens = species name

Classification • System to organize life• Classification System

– Genus = closely related species

– Family = closely related genera

Classification System

• Domain• Kingdom• Phylum• Class• Order• Family• Genus• Species

Largest Level

Smallest Level

Methods of Classification

• Common ancestry is basis for classification

• Taxonomy = science of classifying organisms

• Systematics– Study of diversity of organisms

– Based on evolutionary relationships

Domains of Life

• Archaea

• Bacteria

• Eukarya

Cell Types of Organisms

• Prokaryote– No membrane bound organelles– Genetic material found in a nucleoid

• Eukaryote– Membrane bound organelles– Genetic material in a nucleus

Archaea

• Originally thought to be bacteria

• Live in extreme habitats

• Do not cause disease

• Prokaryotic

• Unicellular

Bacteria

• Found nearly everywhere

• Some cause disease

• Prokaryotic

• Unicellular

Eukarya

• Unicellular or Multicellular

• Eukaryotic cells

• Divided into at least four kingdoms– Protista– Fungi – Plantae– Animalia

Kingdom Protista

• Mostly single cell organisms• May actually be up to 20 kingdoms• Gave rise to other eukaryotes

Kingdom Fungi

• Most are multicellular• Absorptive heterotrophs• Most are saprophites