Until more recent times, scientists namedThings with crazy long names that

Just described the organism.

Apis pubescens, thorace subgriseo,abdomine fusco, pedibus posticisglabis, untrique margine cilatus.

Taxonomy

The science of naming and classifying organisms is called taxonomy.

Until the mid-1700s, biologists named a particular type of organism by

adding descriptive phrases to the name of the genus

A Simpler System

A simpler system for naming organisms was developed by the Swedish biologist Carl Linnaeus

Linnaeus’s two-word system for naming organisms is called binomial

nomenclature

Over the past 250 years since Linnaeus first used two-part binomial

species names, his approach has been universally adopted

Scientific Name

The unique two-part name for a species is now referred to as its

scientific name

The first word is the genus to which the organism belongs. A genus is a

taxonomic category containing similar species

The second word in a scientific name identifies one particular kind of

organism within the genus, called a species. A species is the basic

biological unit in the Linnaean system of classification

With Linnaeus’ system, the honey bee Is now called Apis mellifera.

Classifying Organisms

Linnaeus worked out a broad system of classification for plants and animals

in which an organism’s form and structure are the basis for arranging

specimens in a collection

The genera and species that he described were later organized into a

ranked system of groups that increase in inclusiveness

Similar genera are grouped into a family

Similar families are combined into an order

Orders with common properties are united in a class

Classes with similar characteristics are assigned to a phylum

Similar phyla are collected into a kingdom

Similar kingdoms are grouped into domains

Classification of the Honeybee

Each level of classification is based on characteristics shared by all the

organisms it contains

The honeybee’s scientific name, Apis mellifera, indicates that it belongs to the genus Apis, which is classified in

the family Apidae

All members of the family Apidae are bees that live either alone or in hives,

as does Apis mellifera

What Is a Species?

In 1942, the biologist Ernst Mayr of Harvard University proposed a biologically based definition of

species, which is called the biological species concept

Mayr defined a biological species as a group of natural populations that are interbreeding or that could interbreed,

and that are reproductively isolated from other such groups

Sometimes individuals of different species interbreed and produce

offspring called hybrids

Evaluating the Biological Species Concept

The biological species concept works well for most members of the kingdom

Animalia, in which strong barriers to hybridization usually exist

In practice, modern biologists recognize species by studying an

organism’s features

But the biological species concept fails to describe species that reproduce

asexually, such as all species of bacteria and some species of protists, fungi, plants, and even some animals

Number of Species

The number of species in the world is much greater than the number

described Only about 1.5 million species have

been described to date

Scientists estimate that 5 million to 10 million more species may live in the

tropics alone

Evolutionary History

Classification based on similarities should reflect an organism’s

phylogeny, that is, its evolutionary history

Through the process called convergent evolution, similarities

evolve in organisms not closely related to one another, often because the organisms live in similar habitats

Similarities that arise through convergent evolution are called

analogous characters

Phylogenic Diagram of Mammals

Cladistics

Cladistics is a method of analysis that reconstructs phylogenies by inferring relationships based on

shared characters With respect to two different groups, a character is defined as an ancestral character if it evolved in a common

ancestor of both groups

A derived character evolved in an ancestor of one group but not of the

other

Cladistics is based on the principle that shared derived characters provide

evidence that two groups are relatively closely related

A biologist using cladistics constructs a branching diagram called a cladogram, which shows the evolutionary relationships among groups of organisms Organisms that share derived characters, are grouped together on the cladogram

Cladogram: Mammals, Reptiles, and Birds

Cladogram: Major Groups of Plants

Considering Characters

The great strength of cladistics is objectivity. If a computer is fed the same set of data repeatedly, it will make exactly the same cladogram

every time

The disadvantage of cladistics is that the degree of difference between

organisms is not considered

Cladistic analysis does not take into account variations in the “strength” of

a character, such as the size or location of a fin or the effectiveness of

a lung. Each character is treated equally

Evolutionary Systematics In evolutionary systematics, taxonomists give varying degrees of importance to characters and thus produce a subjective analysis of

evolutionary relationships In this type of analysis, evolutionary relationships are displayed in a

branching diagram called a phylogenic tree

Evolutionary systematics involves the full observational power of the

biologist, along with any biases he or she may have.

Evolutionary Systematics and Cladistic Taxonomy

How many domains are there?

3

The three domains are….

Bacteria, Archaea, Eukarya

Eukarya has 4 kingdoms…

Protista, Fungi, Plantae and Animalia