Classification

Cell Types• Cells come in all types of shapes and sizes.

Cell Membrane – cells are surrounded by a thin

flexible layer• Also known as a plasma membrane

Eukaryotes – are cells that enclose their DNA in

nuclei

Prokaryotes – are cells that do not enclose DNA in

nuclei

Cell Types• Eukaryotic cells have the ability to specialize

• Have a specific function in a multicellular organism • This gives rise to multicellular and more complex

organisms

Cell Types• Prokaryotic cells do not have the ability to

specialize• This limits their ability to form multicellular

organisms• Prokaryotes also need to rely on outside sources to

feed• Eukaryotes have the ability to in some cases

manufacture food.• Eukaryotes have the ability to break down larger

molecules for food

Taxonomy and Evolution

Taxonomy – (a branch of Biology) involves the

identification, naming, and

classification of species• To reduce confusion in discussing organisms

• One goal of taxonomy is to assign a universal scientific name to each known species

Systemics – the science of naming things

Taxon – the groups that systematics organize

living organisms in

DomainsLarger, more inclusive category than a kingdom• Domains:

• Bacteria (corresponds to the kingdom Eubacteria)• Archaea (corresponds to the kingdom Archaebacteria)• Eukarya (corresponds to the kingdoms Fungi, Plantae,

Animalia, and Protista)

Six Kingdom Scheme

• Eubacteria• Archaebacteria• Protist• Fungi• Plantae• Animalia

The Linnaean System of Classification

Developed by botanist Carolus Linnaeus (1707-1778)

The Linnaean System of Classification• Groups of similar (genera – plural of genus) in the same

family• Families placed in orders

• Orders into Classes• Classes into Phyla

• Phyla are grouped into Kingdom

Binomial Nomenclature

• Each species is assigned a two part scientific name• Scientific names are written in italic• First word begins with a capital letter

• Genus• Second word is lowercase

• Species (can interbreed and form fertile offspring)

Modern Evolutionary Classification

Phylogeny – the evolutionary history of lineages• The goal of phylogenetic systematics, or

evolutionary classification, is to group species into larger categories that reflect lines of evolutionary descent, rather than overall similarities and differences

Molecular Data as a Taxonomic Tool

Relatedness is measured by comparing genes and gene products (proteins)

• The more sequences match, the closer they are related.• Molecular data is independent of structural data

• Structural is a traditional method• Accuracy will depend on molecular data supported by

structural data• Fossil data supports:

Whales are closely related to Hippos, pigs, camels…. Supported by molecular data

Phylogenetic Trees

• DNA began a new era in Taxonomy in the 1960’s• Along with computers

• The pattern of branches can tell you how closely related species are• The deeper the “split” the further “away” the

two species are from each other• The closer the “split” the more related

Phylogenetic Trees

Clade – each evolutionary branch in a polygenetic tree

A group of species that include a single common ancestor • Clades can nest within larger clades• Each item in a clade may be an individual species

genus, a family or other taxonomic group

Cladistics• Method mostly used today• Key rule: all organisms of a clade share homologous

structures that do not occur outside the clade

Derived Characters – unique features that unite the

organisms as a clade

Cladogram – links groups of organisms by showing how

evolutionary lines, or lineages, branched off

from common ancestors.

Cladistics

Monophyletic Group – includes a single common

ancestor and all its

descendants

Building A Cladogram

Refer to page 517• Speciation event – when one ancestral species

splits into 2 new ones.• This is the basis of each branch point or node

• The node represents the last point which the 2 lineages shared a common ancestor

• The bottom or “root” of a cladogram represents the common ancestor shared by all of the organisms in the cladogram

Building A Cladogram

• A cladogram’s patterns degrees of relatedness among organisms

Building A Cladogram

Derived Character – A trait that arose in the most recent

common ancestor of a particular lineage

and was passed along to their decedents.

In your Composition Book

Quick Lab• Page 520• Answer all questions

DNA in Classification

• All organisms carry genetic information in their DNA• Passed on from earlier generations

• Many different organisms share many genes and show important homologies that can be used to determine evolutionary relationships

• Using DNA has made evolution more accurate

Molecular Clock• Method used by researchers that uses mutation

rates in DNA to estimate the length of time that 2 species have been evolving independently