The Origin and Classification of Life

Classification and Evolution of Organisms

Taxonomy

• Taxonomy is the science of naming organisms and grouping them into categories.

• Derived from the Greek word taxis, which means arrangement.

Binomial System of Nomenclature

• The binomial system of nomenclature was developed by Carolus Linnaeus in 1758.

• The system uses only two latin names – the genus and the specific epithet for each species of organism.

Carolus Linnaeus

Binomial System of Nomenclature

• A species is a population of organisms capable of interbreeding and producing fertile offspring.

• A genus is a group of closely related organisms.

Hierarchy of Classification

Domains

• A Domain is the largest category of organisms.• There are three main domains: Eubacteria,

Archaea, and Eucarya.• The Eubacteria and Archaea are prokaryotic

and the Eucarya are eukaryotic.

Domains of Life

Kingdom

• A kingdom is a subdivision of a domain.• There are several kingdoms within the

Eubacteria and Archaea based primarily on differences in the metabolism and genetic composition of the organisms.

Kingdom

• There are four kingdoms within the Domain Eucarya.– Plantae– Animalia– Fungi– Protista (protozoa and algae)

Kingdoms

Phylum

• A phylum is a subdivision of a kingdom.• Organisms are based into phyla based upon

careful investigation of their structure, metabolism, and biochemistry.

Phylum

• An attempt is made to classify natural groups rather than imposing artificial subdivisions.

• Only flowering plants produce flowers and have seeds; conifers lack flowers but have seeds in cones; ferns lack flowers, cones, and seeds; and mosses lack tissues for transporting water.

Class

• A class is a subdivision within a phylum.• Within the phylum Chordata within the the

kingdom Animalia, there are seven classes: mammals, birds, reptiles, amphibians, and three classes of fish.

Order

• An Order is a category within a class.• The order Carnivora is an order of meat-eating

animals within the class Mammalia.

Family

• A Family is a subdivision of an order that consists of a group of closely related genera, which in turn are composed of closely related species.

Family

• The cat family, Felidae, is a subgroup of the order Carnivora; it includes many species in several genera, including the Canada lynx and bobcat (genus Lynx); the cougar; the leopard, tiger, jaguar, and lion (genus Panthera); the house cat (genus Felis); and several other genera.

All Life On Earth

Kingdom: Animalia

Phylum: Chordata

Class: Mammalia

Order: Rodentia

Family: Sciuridae

Genus: Sciurus

Species: Vulgaris

Classification of HumansTaxonomic Category

Human Classification

Characteristics Other Representatives

Domain Eucarya Cells containing a nucleus and other organelles

Plants, animal, fungi, protozoa, algae

Kingdom Animalia Eukaryotic heterotrophs, usually motile, specialized tissues

Sponges, jellyfish, worms, clams, insects, snakes, ctas

Phylum Chordata Stiffening rod down back

Fish, amphibians, reptiles, birds, mammals

Classification of HumansTaxonomic Category

Human Classification

Characteristics Other Representatives

Class Mammalia Hair and mammary glands

Kangaroos, mice, whales, skunks, monkeys

Order Primates Relatively large brain and opposable thumb

Monkeys, gorillas, chimpanzees, baboons

Family Hominidae Primates that lack a tail and have an upright posture

Humans and extinct relatives (australopithecus, Paranthropus, Homo)

Classification of HumansTaxonomic Category

Human Classification

Characteristics Other Representatives

Genus Homo Hominids with large brains

Humans are the only surviving member of the genus (past members: homo erectus, homo neanderthalensis)

Species Homo Sapiens Humans

Phylogeny

• Phylogeny is the science that explores the evolutionary relationships among organisms, seeking to reconstruct evolutionary history.

• Taxonomists and phylogenists work together, so that the products of their work are compatible.

Evidence Used to Establish Phylogenetic Relationships

• Several lines of evidence are used to develop evolutionary histories: fossils, comparative anatomy, life cycle information, and biochemical and molecular evidence.