Organisms can be classified based on physical similarities. How would you classify the organisms in your envelope?

Archaeabacteria - 1 Bacteria – 2 Protists – 2 Fungi – 3 Plants – 2 Animals – 6

How to use a Dichotomous Key GkL3Ow4 GkL3Ow4 ets/dichotomous_key_smilies.html Model of a Dichotomous Key

Di = Two Follow the steps until you reach the common name or scientific name

Taxonomy is the science of naming and classifying organisms. It was started by Carl Linnaeus. A taxon is a group of organisms in a classification system. White oak Quercus alba

Binomial nomenclature is a two-part scientific naming system using Latin. Tyto (genus) Alba (species) Scientific Name

Scientific names help scientists to communicate. –Some species have very similar common names. –Some species have many common names.

Linnaeus’ classification system has seven levels. Each level is included in the level above it. Levels get increasingly specific from kingdom to species.

Levels of Classification 2 Domain Kingdom Phylum Class Order Family Genus Species Only members of the same species can produce fertile offspring. Scientific Name = Genus and Species

The Linnaean classification system is limited. Linnaeus taxonomy doesn’t account for DNA evidence. –The technology didn’t exist during Linneaus’ time. –Linnaean system based only on physical similarities.

Which is more closely related to a manatee, a seal or an elephant?

Seal or Elephant

Physical similarities are not always the result of close relationships. Genetic similarities more accurately show evolutionary relationships.

The elephant’s DNA is more closely related to the manatee.

Small evolutionary scars: Manatee flipper toe nails

A common method is to make evolutionary trees. –classification based on common ancestry –species placed in order that they descended from common ancestor

An evolutionary tree made by showing common ancestors. –A clade is a group of species that shares a common ancestor. –Each species in a clade shares some traits with the ancestor. –Each species in a clade has traits that have changed.

Molecular data may confirm classification based on physical similarities. Molecular data may lead scientists to propose a new classification. Molecular evidence reveals species’ relatedness. DNA is usually given the last word by scientists.

Molecular clocks use mutations to estimate evolutionary time. Mutations are thought to add up at a constant rate in related species. –As more time passes, there will be more mutations. DNA sequence from a hypothetical ancestor The DNA sequences from two descendant species show mutations that have accumulated (black). The mutation rate of this sequence equals one mutation per ten million years. Mutations add up at a fairly constant rate in the DNA of species that evolved from a common ancestor. Ten million years later— one mutation in each lineage Another ten million years later— one more mutation in each lineage

The current tree of life has three domains.

Classification is always a work in progress. The tree of life shows our most current understanding. New discoveries can lead to changes in classification. –Until 1866: only two kingdoms, Animalia and Plantae Animalia Plantae

The tree of life shows our most current understanding. New discoveries can lead to changes in classification. –Until 1866: only two kingdoms, Animalia and Plantae –1866: all single- celled organisms moved to kingdom Protista Animalia Protista Plantae

The tree of life shows our most current understanding. New discoveries can lead to changes in classification. –Until 1866: only two kingdoms, Animalia and Plantae –1938: prokaryotes moved to kingdom Monera –1866: all single- celled organisms moved to kingdom Protista Animalia Protista Plantae Monera

The tree of life shows our most current understanding. New discoveries can lead to changes in classification. –Until 1866: only two kingdoms, Animalia and Plantae –1938: prokaryotes moved to kingdom Monera –1866: all single-celled organisms moved to kingdom Protista Monera –1959: fungi moved to own kingdom Fungi Protista Plantae Animalia

The tree of life shows our most current understanding. New discoveries can lead to changes in classification. –Until 1866: only two kingdoms, Animalia and Plantae –1938: prokaryotes moved to kingdom Monera –1866: all single-celled organisms moved to kingdom Protista –1959: fungi moved to own kingdom –1977: kingdom Monera split into kingdoms Bacteria and Archaea Animalia Protista Fungi Plantae Archea Bacteria

The three domains in the tree of life are Bacteria, Archaea, and Eukarya.

Three Big Questions 1.Does it’s cell have a nucleus? Do carry – Eukaryote There’s No – Prokaryote 2. How many cells? One – Unicellular Many – Multi-cellular 3. How does it obtain sugar? Take it in – Heterotroph Make it – Autotroph How do we know which kingdom organisms belong to? We ask three simple questions:

Domain Bacteria includes prokaryotes –one of largest groups on Earth –classified by shape, need for oxygen, and diseases caused

–known for living in extreme environments Domain Archaea includes prokaryotes –cell walls chemically different from bacteria –differences discovered by studying RNA

Bacteria and archaea can be difficult to classify. –transfer genes among themselves outside of reproduction blurs the line between “species” –more research needed to understand prokaryotes bridge to transfer DNA

Domain Eukarya includes all eukaryotes. Kingdom Protista - “pond scum” of the earth - lots of variations

–kingdom Protista –kingdom Plantae Multicellular producers Domain Eukarya includes all eukaryotes.

–kingdom Protista –kingdom Plantae –kingdom Fungi Decompose through absorption Domain Eukarya includes all eukaryotes.

–kingdom Protista –kingdom Plantae –kingdom Fungi –kingdom Animalia Multicellular consumers Domain Eukarya includes all eukaryotes.