Alberts, B

ray, H

opkins, Johnson

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings

Professor: Dr. Barjis

Room: P313

Phone: (718)2605285

Email: ibarjis@citytech.cuny.edu

General BiologyS

ylvia S M

ader

Lecture 1: Chapter 20

Classification of Living Things

Outline

• Taxonomy– Binomial System

• Species Identification• Classification Categories• Phylogenetic Trees

– Tracing Phylogeny• Cladistic Systematics• Phenetic Systematics• Classification Systems

Taxonomy (arrange” and “law )

• Taxonomy is the branch of biology dealing with the naming, identification, and classification of organisms.

• Taxonomy uses a binomial system developed by Linnaeus.

• Taxonomy uses reproductive isolation as the basis of definition of a species.

• taxonomists use following categories of classification: domain, kingdom, phylum, class, order, family, genus and species

Classifying Organisms

Binomial System

• In mid-eighteenth century, Linnaeus developed the binomial system of naming species.– First word is genus.– Second word (specific epithet) refers to

one species within genus.A species is designated by the full

binomial name (Genus species). Genus can be used to refer to group

of related species.

Species Identification

– Character traits are used to distinguish one group from another are:

structural features. chromosomal. molecular features.

– A primitive character is one that is present in the common ancestor and all members of a group

– Early biologists referred to animals as ‘‘simple’’ and ‘‘advanced,’’ but now it is more accurate to use the terms: ‘‘primitive’’ and ‘‘derived,’’

Classification Categories

• Modern taxonomists use the following classification:– Species– Genus– Family– Order– Class– Phylum– Kingdom– Domain

Classification Categories

• The higher the category, the more inclusive.• Organisms in the same domain have

general characteristics in common.

Phylogenetic (tribe” and “producing”) Trees

• Systematics is the study of the diversity of organisms at all levels of organization.

• One goal of systematics is to determine phylogeny or evolutionary history of organisms by gathering

– Fossil Record - – Homology –– Molecular Data

Protein comparison RNA and DNA comparison DNA hybridization Molecular Clock

Phylogenetic (tribe” and “producing”) Trees

• Phylogenetic tree is a diagram that: – Indicates common ancestors and lines of

descent.– Explain similarities and differences among

modern living groups.– Reflect patterns of shared and unique

sections of DNA among groups of animals.

Classification and Phylogeny

Tracing Phylogeny

• Fossil Record– Fossil record is incomplete; thus, it is often hard

to tell to which group a fossil is related.• Homology is character similarity stemming from a

common ancestor.– Convergent evolution is similarities in structure

in distantly related groups due to adaptation to the environment

– Parallel evolution similarities in structure in related group that cannot be traced to a common ancestor.

Tracing Phylogeny

• Molecular data– Protein comparison- distinction between

two organisms are determined by sequencing of amino acids

– DNA and RNA comparison, – DNA hybridization, – Molecular clock

Systematics Today

• There are three main schools of systematics today– Cladistic– Phenetics– Traditional

Cladistic Systematics

• Uses shared derived characters to classify organisms and arrange taxa (like phylogenetic tree) called cladogram.

Phenetic Systematics

• In phenetic systematics, species are classified according to the number of their similarities.– Ignores the possibility that some of the

shared characteristics are probably the result of convergence or parallelism.

Traditional Systematics

• Traditional systematics mainly use anatomical data to classify organisms and construct phylogenetic trees based on evolutionary principles.– Stress both common ancestry and degree

of structural difference among divergent groups.

Not strict in making sure all taxa are monophyletic.

Five-Kingdom System

The evolution of organisms in the five kingdoms is most accurately described as Monera to Protists, from Protists separately to Fungi, Plants, and Animals

Three-Domain System

• Molecular data suggest there are two groups of prokaryotes, the bacteria and archaea, that are so different, they should be assigned to separate domains.

Three-Domain System

– Archaea live in extreme environments. Methanogens Halophiles Thermocidophiles

Three-Domain System

• Domain Eukarya contains unicellular and multicellular organisms whose cells have a membrane-bound nucleus.– Sexual reproduction common.– Contains 4 kingdoms:

ProtistaAnimalsFungiPlants

Review

• Taxonomy– Binomial System

• Species Identification• Classification Categories• Phylogenetic Trees

– Tracing Phylogeny• Cladistic Systematics• Phenetic Systematics• Classification Systems