Classification Chapter 18. Classifying Organisms

Classification

Chapter 18

Classifying Organisms

• TAXONOMY is the study of how scientists classify organisms– The various levels of organization are called

TAXONS.

• Classification is a way for scientists to name and group organisms in an organized manner.

Classifying Organisms (cont)

• Ancient philosophers used to classify organisms based off of visible characteristics, but as we have discovered more organisms, we have changed the system.

• Most of you are probably familiar with the system created by CAROLUS LINNAEUS, which is based off of different levels of organization.

Classifying Organisms (cont)

LARGEST LEVEL

SMALLEST LEVEL

KingdomPhylum

ClassOrderFamilyGreenSpecies

Classifying Organisms (cont)

Classifying Organisms (cont)

• You can remember the order with the following sentence:

• Kings Play Cards On Fat Green Stools.

Classifying Organisms (cont)

• All living things have two names usually from Latin that describes an essential trait. This process of giving all living things two name is called BINOMIAL NOMENCLATURE.

• Tips on naming organisms:– The first name is the genus and the second is the species– The whole name is italicized– Genus is capitalized

• Example: – Homo sapiens is the term for humans. Homo = man / same, sapiens

= wise

Modern Classification

• While we still use the Linnaeus system and binomial nomenclature, there is one major difference in modern classification.

• ORGANISMS ARE CLASSIFIED ACCORDING TO THEIR PHYLOGENY, EVOLUTIONARY DESCENT, NOT JUST THEIR PHYSICAL APPEARANCE!!

Modern Classification (cont)

• Evolutionary relationships are shown using CLADOGRAMS like this one.

• According to this cladogram, primates and rabbits shared a common ancestor more recently than primates did with sharks.

According to this cladogram, which dinosaur is most closely related to modern birds?

How do scientists determine evolutionary relation?

• Physical similarities• Fossil record• Embryology• Geographic evidence• Homologous, analogous, &

vestigial structures• Genetic similarities in DNA &

RNA

Modern Classification (cont)

• Another difference with modern classification is that we have an added taxon: DOMAIN.

• There are three domains: BACTERIA, ARCHAEA, and EUKARYA.

Bacteria

• Bacteria DO NOT have a nucleus

• Are unicellular

• Have cell walls

• Can be either autotrophs or heterotrophs

Archaea

• Archaea DO NOT have a nucleus

• Live in extreme environments like volcanoes, hot geysers, depths of the oceans, etc

• Are unicellular

• Have cell walls

• Can be either autotrophs or heterotrophs

Eukarya

• Have a nucleus

• Usually multicellular but occasionally unicellular

• Have four kingdoms:– Protista (autotroph or heterotroph)– Fungi (heterotroph)– Plantae (autotroph)– Animalia (heterotroph)

Eukarya (cont)

Protista Fungi

Eukarya (cont)

Plantae Animalia

Patterns of Evolution

• ADAPTIVE RADIATION: when one species branches off into numerous other species– Example: Darwin’s finches all evolved from

ONE species.

• CONVERGENT EVOLUTION: due to similar lifestyles, some organisms evolve similar adaptations.– Example: Sharks, penguins, and dolphins are

not closely related, BUT they all have flippers and pointed heads/beaks to be excellent swimmers.

Patterns of Evolution (cont)

• CO-EVOLUTION: when two organisms evolve together– Example: Bees and flowers have evolved a mutual

relationship. Bees pollinate flowers and flowers provide bees with nectar to make honey.

• MASS EXTINCTION: occurs when a huge percentage of species dies out– Example: When a meteor struck Earth 65 mya, the

dust in the atmosphere blocked the sun, which killed most plants and, in turn, most animals.

Patterns of Evolution (cont)

• GRADUALISM: slow, continued evolution– Example: Over millions of years, horse have become

larger.

• PUNCTUATED EQUILIBRIUM: this describes sudden bursts evolution– Example: A severe drought could kill all trees with

juicy fruit in a few years. As a result, the only surviving birds in that time would include those with small, hard beaks to eat tiny seeds.

Gradualism vs. Punctuated Equilibrium