T he Origin of Life. Life originated 3.5-4.0 billion years ago! What came first: prokaryotic cells or eukaryotic cells?. Prokaryotes. Prokaryotes dominated life on Earth from 3.5-2.0 bya ! The 1 st actual cells. 3.5 billion year old fossil of bacteria. Modern bacteria.
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The Origin of Life • Life originated 3.5-4.0 billion years ago! What came first: prokaryotic cells or eukaryotic cells?
Prokaryotes • Prokaryotes dominated life on Earth from 3.5-2.0 bya! • The 1st actual cells 3.5 billion year old fossil of bacteria Modern bacteria Chains of unicellular cyanobacteria
How many species exist on Earth? • We don’t know an exact number • MILLIONS • Thousands still waiting to be discovered! How do we keep track of all of them?
What is classification? • The arrangement of objects, ideas, or information into groups by finding common traits or characteristics Imagine what a trip to the grocery store would be like if the items weren’t categorized!
What is the purpose of classification? • To logically organize the approximately 1.5 million species that we have on Earth! • The classification of species is based on DNA, development, reproduction, morphology, & physiology.
The History of Organization • Aristotle (384-322 BCE): interested in biological classification & patterns in nature • Aristotle’s classification system of life consisted of 2 categories: • Organisms with blood • Organisms without blood
The History of Organization • Carl Linnaeus (1707-1778): the Father of Biological Classification • Developed a 2-word naming system called binomial nomenclature • This system involves the assigning of a 2-part scientific name to each species.
All the same species! • There are at least 50 different names for the species of cat shown before. • Different places have different names. • Scientific name: Felisconcolar • Why is it important to have scientific names?
Binomial Nomenclature • The 2-part scientific name of a species consists of the name of the genus (1st part of the name) & the name of the specific epithet(2nd part of the name). • Both are underlined when written, or in italics when typed. • The 1st is capitalized & the 2nd is lower case. Turdusmigratoriusis the scientific name of the American Robin!
Common Name: Black Bear Scientific Name: Ursusamericanus Common Name: Polar Bear Scientific Name: Ursusmaritimus
Why is Latin used when naming species? • Common names are not universal & meanings of words change over time • “Possums” in America are NOT “possums” in Australia! (Didelphisvirginianavs. Trichosurusvulpecula) • It is a “dead language” so it will not change over time. • Comes from the way organisms are classified
Taxonomy • The science of classification • Scientists who classify or organize organisms into related groups are called taxonomists. • Taxonomists study taxonomy & the groupings are called “taxa”. Cheetahs & Leopards belong to the same family, but different genus.
Linnaean Hierarchical System of Classification • Largest to Smallest: taxonomic categories Domain Kingdom Phylum Class Order Family Genus Species Broad Every species on Earth can be classified into a domain. Those domains can be further broken down & separated until you have individual species! Specific
Coral snake Albert squirrel Sea star Grizzly bear Black bear Giant panda Red fox KINGDOM Animalia PHYLUM Chordata CLASS Mammalia ORDER Carnivora FAMILY Ursidae GENUS Ursus SPECIES Ursus arctos Least specific Most specific
Human Linnaean Classification Notice how we went from broad categories to specific categories!
A good way to remember: Domain Kingdom Phylum Class Order Family Genus Species Dear King Phillip Came Over For Good Soup
What genus does the American Robin belong to? American Robin Turdus Migratorius Turdus! Remember that species get their scientific names from their classification – Genus species Turdusmigratorius
Which species are more closely related? Polar & Grizzly Bear – they belong to the same genus! Panda & Polar Bear Polar Bear & Grizzly Bear Grizzly Bear & Panda
Which taxonomic group is the most broad (the largest)? • Kingdom • Phylum • Order • Species Kingdom!
Which taxonomic group is the most specific? • Kingdom • Phylum • Order • Species Species!
Which taxonomic group is the more specific than order but broader than genus? • Kingdom • Family • Order • Species Family!
Why is taxonomy important? Remember! Science changes all the time – nothing is concrete! • Unknown species are being discovered! • New fossils are being uncovered! How would these new discoveries affect our classification systems?
Cladograms/Phylogenetic Trees • Diagrams showing evolutionary relationships (the family tree of the species) • Constructed using morphology & DNA evidence to order the organisms in sequence.
Cladograms/Phylogenetic Trees • Important Features: • Derived Characteristics: recently evolved characteristics of organisms being compared • Ancestral Characteristics: shared characteristics of all the organisms being compared
Ancestral Characteristics: vertebrae Derived Characteristics: hair, amniotic egg, etc.
Which organisms are rabbits most closely related to? • Crocodiles • Ray-finned Fish • Birds • Primates Primates!
Which organisms are birds the least related to? • Crocodiles • Ray-finned Fish • Sharks • Primates Sharks!