Chapter 18

The History of Life

Why Classify?

• So that scientists can identify what organism they are discussing or studying. •

Taxonomy:

A discipline where scientists classify organisms and assign each organism a universally accepted name.

Common Names vs Scientific Names

• Common names: – Mountain Lion – Puma – Cougar – Panther • Scientific name: –

Felis concolor

•

Binomial Nomenclature (Carolus Linnaeus)

A two-part scientific name that is assigned to an organism. Both names are written in italics. – First part is: (Upper case)

Genus

– Second part is: (lower case)

species

• Example: Humans= Homo sapiens (“wise man”)

The Three Domain System

• Domain: more inclusive category than any other. Larger than kingdom.

• • • Eukarya: Bacteria: Archaea: Protista, Fungi, Plantae, Animalia Eubacteria Archaebacteria

Carol Linnaeus

• Carol Linneaus divided organisms into plants and animals. (problem?) • This didn’t cover all of the diversity of life.

– Scientists came up with other kingdoms.

– Monera, Protista, Fungi, Plantae, Animalia • Then they developed the 6-kingdom system that we still use today: – Eubacteria, Archaebacteria, Protista, Fungi, Animalia, Plantae.

DOMAIN→ ARCHAEA BACTERIA EUKARYA EUKARYA EUKARYA EUKARYA KINGDOM → CELL TYPE

Prokaryote or Eukaryote

ARCHAEBACTERI EUBACTERIA PROTISTA

PROKARYOTE PROKARYOT E

NUMBER OF CELLS

Unicellular or Multicellular

CELL NUCLEUS

Present or Absent

CELL WALL CELL WALL COMPOSITI ON NUTRITION

Autotroph Heterotroph

LOCOMOTI ON

UNICELLULAR NO YES IF THEY HAVE FLAGELLA UNICELLULA BOTH NO YES YES WITHOUT PEPTIDOGLYCAN BOTH WITH PEPTIDOGLY CAN BOTH YES IF THEY HAVE FLAGELLA YES YES WITH BOTH YES

FUNGI

EUKARYOTE EUKARYOTE BOTH YES YES WITH NO

PLANTAE

EUKARYOTE MULTICELL.

YES YES WITH CELLULOSE HETEROTROPH AUTOTROPH NO

ANIMALIA

EUKARYOTE MULTICELL.

YES NO NONE HETEROTROPH YES

• • • • •

Domain:

Eukarya (all eukaryotic organisms)

KINGDOMS

:

Protista:

– have the greatest variety unicellular & multicellular – Some photosynthetic, others heterotrophic – 3 types: plant-like, animal- like, fungus-like

Fungi:

– – – Heterotrophs Unicellular & multicellular Have cell walls of chitin

Plantae:

– – – Multicellular Cell wall of cellulose Autotroph

Animalia:

– – Multicellular Heterotroph

•

Domain: Archaea Kingdom: Archaebacteria

– – – – Prokaryotic Unicellular Have cell wall

WITHOUT

peptidoglycan Autotroph and Heterotroph •

Domain: Bacteria Kingdom: Eubacteria

– Prokaryotic – Unicellular – Have cell wall

WITH

peptidoglycan – Autotroph and heterotroph

Classify these Organisms

• • • • • • • Kingdom: Phylum: Class: Order: Family: Genus: Species: Animalia Chordata Mammalia Primates Hominidae

Homo sapiens

•

Evolutionary Classification

similarities : Biologists now group organisms into categories that represent lines of evolutionary descent, or phylogeny, not just physical •

Cladogram:

cladogram.

Characteristics that appear in recent parts of a lineage but not in its older members are called derived characters and can then be used to construct a

Molecular Clocks (DNA and RNA)

• The genes of many organisms show important similarities at the molecular level. Similarities in DNA can be used to help determine classification and evolutionary relationships.