Classification

(aka

Taxonomy) Living Environment

Why must we classify?

There are SO MANY critters out there!

How do we know who’s who and what’s

what?

Biologists use a classification system to

name organisms and group them in a

logical manner.

This is known as TAXONOMY!

Taxonomy

The discipline in which scientists classify

organisms and assign each organism a

universally accepted name.

Why do they need a “special name”?

Mountain Lion

Puma

Cougar

Catamount

Panther

Ghost Cat

Indian Devil

Ok you get the point…

The mountain lion is known to people all

over the world by different names

In the English language alone, it has 40

different names

That’s why we need a standardized

naming system! So everyone knows what

you’re talking about!

How do they do it?

When taxonomists classify organisms, they organize them into groups that have biological significance

This requires smaller as well as larger categories

Organisms are placed into a particular group with organisms that are more similar to each other than they are to organisms in other groups

18th Century

Back in to good old days European

scientists recognized that referring to

organisms by common name was way

too confusing!

Common names are different everywhere

you go!

Ex.) In the UK buzzard means hawk, but in

the US a buzzard is a vulture

18th Century

Scientists used Latin and Greek during the

18th century

They agreed to come up with a single

name for a species and they used Greek

or Latin to assign those names

We still use Greek or Latin for new

organisms that are discovered today

First Attempt at Naming

The earliest names tried to describe physical

characteristics of a species in great detail

This lead to names being up to 20 words long

NOT PRACTICAL

Ex.) An oak tree “Oak with deeply divided

leaves that have no hairs on their undersides

and no teeth around their edges.”

Binomial Nomenclature

A two-word naming system developed by Carolus Linnaeus

This system is still used today

The name is two words

First word is CAPITALIZED and is the GENUS

Second word is LOWERCASE and is the SPECIES

Italicized when typed and underlined when handwritten

Ex.) Ursus arctos

AKA Grizzly Bear

The first word is the genus

A genus is a group of closely related

species

What’s the genus in the example?

The second word is the species

A species is unique within the genus

What’s the species in the example?

More Bears

All have the same first word Ursus

Ursus arctos grizzly bear

Ursus maritimus polar bear

Ursus americanus american black bear

Ursus thibetanus asian black bear

Levels of Organization Each level is referred to as a taxon or

taxonomic category

From largest to smallest:

Kingdom

Phylum

Class

Order

Family

Genus

Species

Kingdom Largest and most inclusive category

Phylum Several different classes make up a

phylum

Class Composed of similar orders

Order A broad taxonomic category composed

of similar families

Family Genera that share many characteristics

Genus & Species The lowest two levels that help to identify

an organism

How the heck will I remember

this?

Simple!

King Phillip Came Over For Good

Spaghetti

Kingdom, Phylum, Class, Order, Family,

Genus, Species

Biomagnification

The increasing concentration of pesticides

or other toxic materials in living organisms

via the food chain.

Ecological Efficiency and

Biomagnificiation

Pesticides and toxic materials that

accumulate via biomagnification

CANNOT be metabolized.

Individuals cannot use them as a source

of energy.

Biomag. Cont’d

As the organism takes in food and uses its

energy, CO2 and H2O are returned to the

atmosphere but the pesticides remain.

The pesticides accumulate in the

organism’s tissue over its lifetime.

Increases by Trophic Level

Amplified by the flow of energy b/t

trophic positions

Each organism that eats a “toxic”

organism from a lower trophic position will

have a toxic concentration greater than

the organism that it ate.

Example: Osprey

Eats large bluefish that have

concentrations of pesticides up to 10x

greater than Atlantic silversides (smaller

fish).

Modern Evolutionary

Classification Scientists used to classify organisms based on

similarities in appearance

We know that doesn’t work!

Ex.) A shark and dolphin look alike, but they are not

closely related

Study of Phylogeny

Phylogeny is the study of evolutionary

relationships among organisms

Biologists now group organisms into

categories that represent lines of

evolutionary descent, or phylogeny, not

just physical similarities

Phylogenetic Trees

Family trees that hypothesizes about the

evolutionary relationships thought to exist

between different organisms

Evidence used for Phylogentic

Trees

1. DNA

2. Embryology

3. Fossil Record

4. Morphology (Comparative Anatomy)

To aid in making phylogenetic trees, a combination of these lines of evidence are used:

DNA

Embryology

Fossil Record

Morphology

Hyraxes and elephants share similar morphology:

1. Tusks that develop from incisors rather than canines

2. Similar foot and skull structure.

3. 4 toes on forelimbs, 3 toes on hind limbs.

4. Rounded hoof-like nails.

5. Internal testicles in males.

6. Mammary glands on females between forelimbs.

But…

Despite the fact that the dugong looks even nothing like either the elephant or the hyrax, it is a close relative…

This can be seen in the dugong’s skeletal structure (especially its limbs) which is similar to the hyrax and elephant even though its limbs serve very different functions. This is called HOMOLOGY.

Homologous Structures - characteristics in different organisms that carry out different functions and which may appear superficially different but which were inherited from a common ancestor that also had that character – share an evolutionary history.

Homology is caused by ADAPTIVE RADIATION

Adaptive radiation –

When an ancestral species diversifies rapidly and

gives rise to a variety of new physiological forms

that fill different ecological niches.

Sometimes, morphology can be misleading…

These animals have evolved similar adaptations for obtaining food because they occupy similar niches. What can you infer about their phylogeny from their geographic locations?

Analogous Structures = traits that are superficially

similar and which carry out the same function but

which have separate evolutionary origins.

Analogous Structures are caused by CONVERGENT

EVOLUTION • the process whereby organisms not closely related,

independently evolve similar traits as a result of having to adapt

to similar environments or ecological niches.

Structural patterns are clues to the history of a species.

Vestigial structures are remnants of organs or structures that had a function in an early ancestor.

Examples include ostrich wings, human appendix, and wisdom teeth, whale and snake pelvis/hind legs

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Pythons have tiny femurs (leg bone)

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Cladistics

A relatively new system of phylogenetic

classification that uses shared derived

characteristics to establish evolutionary

relationships

Cladograms

Use characteristics that appear in the recent

parts of a lineage but not in its older members

These are called derived characteristics

A feature that only evolved within the group under consideration

Derived characteristics can be used to

construct a cladogram

A diagram that shows the evolutionary

relationships among a group of organisms

Help scientists see evolutionary

relationships

The last common ancestor is

where lines last connected

Three Basic Assumptions of

Cladistics

1. Organisms within a group are

descended from a common ancestor

2. There is a branching off from common

ancestor showing a new species is

formed

3. Change in characteristics occurs in

lineages over time

Perhaps the first and most

important split in the tree of life is

what separates the two types of

cells that represent life on Earth.

Prokaryotic Cell

• Unicellular

• No nuclear membranes

(nucleus)

• Instead there is a nucleoid

region

• No membrane bound

organelles

• Appeared around 4 billion

years ago

Eukaryotic Cell

• Can be

unicellular or

multicellular

• More advanced

than prokaryotes

• Nucleus present

(nuclear

membrane)

• Membrane

bound organelles

• Appeared about

1 billion years

ago

Three Domains

Domains are the most inclusive category.

Larger than kingdoms

There are three domains:

1. Bacteria

2. Archaebacteria

3. Eukarya

Domain Bacteria

Unicellular organisms

Prokaryotic

Thick, rigid cell walls that surround a cell

membrane

Contain peptidoglycan (made of sugars

and amino acids)

Very diverse bacteria ranging from

harmless to deadly

Domain Archaea

Unicellular and prokaryotic

Live in some of the most extreme

environments imaginable

Hot springs, brine pools, mud without

oxygen

Cell walls lack peptidoglycan

Cell membranes are made of lipids that

are not found in other organisms

Domain Eukarya

Consists of all organisms that have a

nucleus

Composed of very diverse organisms that

make up four kingdoms

Kingdoms Kingdoms are the second highest rank below

domain

They are composed of smaller groups called phyla

There are currently six kingdoms: 1. Eubacteria

2. Archaebacteria

3. Protista

4. Fungi 5. Plantae

6. Animalia

Eubacteria

The only kingdom in the domain Bacteria

They are very diverse bacteria that may

make you sick or help you stay healthy

Can be autotrophic or heterotrophic

Ex.) Streptococcus or Escherichia coli

Archaebacteria

Only kingdom in the domain Archaea

Can be autotrophic or heterotrophic

Ex.) methanogens & halophiles

Protista

Composed of eukaryotic organisms that cannot be classified as animals, plants, of fungi

Members display great variety

Most are unicellular, but not all

Can be photosynthetic or autotrophic

Can share characteristics with plants, fungi, or animals

Ex.) algae

Fungi

Heterotrophs

Most feed on dead or decaying organic

matter

Secrete digestive enzymes into their food

source and absorb the smaller food

molecules into their bodies

Ex.) mushrooms & yeast

Plantae

Multicellular organisms

Photosynthetic

Autotrophs

Nonmotile – can’t move from place to

place

Cell walls with cellulose

Animalia

Multicellular

Heterotrophic

Lack cell walls

Motile (mostly) – can move about at least

for part of their life cycle

Dichotomous Key

Device used to identify an organism

based on previous descriptions

Follow a series of steps to find the identity

of the organism

Sequence of choices between two

statements that lead you to another

choice

Sort of like a treasure hunt!

1.

A. one pair of wings

B. Two pairs of wings