Topic 5.5 - Classification

What is Taxonomy?

• Systematics is the study of the diversity of life and its evolutionary history

• Systematics is combinaton of several sciences:

1. Taxonomy is science of naming and arranging living organisms into groups

2. Phylogeny is the evolutionary history of an organism or group

Goals of Taxonomy

Three important goals:

1. Sort out closely related organisms into individual species

2. Assign a single universal name to all living organisms

– Necessary to facilitate communication between all scientists worldwide

3. To place all living organisms into groups with real biological meaning.

Benefits of Taxonomy

• Species Identification – a system allows us to quickly identify organisms

• Predictive value – if several members of a group have a common trait, another species will probably have that trait too

• Evolutionary links – species in the same group probably share a common ancestor – helps indicate how they evolved

The Beginnings of Classification

• The first classification scheme was developed by Aristotle about 2000 years ago

Aristotle’s System

• Artistotle grouped organisms into:

Plants

And

Animals

Changing the System

• Aristotle’s system was used until the 1400s– At that point “modern,” science was

beginning to realize that system was too simplistic

– Too often names for species varied from location to location and did not accurately describe the organism.

Carolus Linneaus

• Swedish Biologist who developed the basis for the classification system still in use today (mid 1700s)

• Utilized morphology (structure and function) to classify all living organisms

Linneaus’s System

• Linneaus created a “filing,” system for grouping organisms

• Hierarchy of increasingly more general categories:– Species are grouped into genera ( sing. genus)– Genera into families– Families into orders– Orders into classes– Classes into phyla (sing. phylum)– Phyla into kingdoms 5.5.2

• Each group is called a taxon (plural taxa)

• Individual species are classified into a series of taxa – each one larger than the previous one

Linneaus’s System

5.5.2

An Example - Human Classification

• Kingdom: Animalia

– Phylum: Chordata

• Class: Mammalia–Order: Primate

» Family: HominidaeGenus: Homo

Species: sapien

Larger group

Smaller group

5.5.2

Another Example - Corn Classification

• Kingdom: Plantae

– Phylum: Magnoliophyta

• Class: Liliopsida–Order: Cyperales

» Family: PoaceaeGenus: Zea

Species: mays

Larger group

Smaller group

5.5.2

Linneaus’s System

• Linneaus assigned each species a two-part scientific name – binomial nomenclature

• Why mostly Latin or Greek?

• First name – Genus

• Second name – species

5.5.1

Binomial Nomenclature

Canis familiaris 5.5.1

Binomial Nomenclature

Rules for naming organisms:1. The genus name is always upper-

case.2. The species name is always lower-

case3. Italics are used if the name is printed

(typed)4. Handwritten names are underlined

with two separate lines. 5.5.1

Modern Classification

• Linneaus only created two kingdoms for living organisms – plants and animals – why?

• Modern taxonomists argue about the number of kingdoms – five or six– Prokaryote (monera) – archaebacteria and

eubacteria?– Protoctista (protist)– Fungi– Plantae– Animalia

Kingdom Plantae

• All organisms in Kingdom Plantae have the following characteristics:– Multicellular– Eukaryotic– Photosynthetic autotrophs– Almost all terrestrial

• Plants are divided into divisions (instead of phyla) based on evolutionary characteristics

5.5.3

Division Bryophyta

• Display evolutionary adaptations that helped bryophytes move from water to land:– Covered with a waxy cuticle – why?

• However, bryophytes are NOT totally independent of water.– Flagellated sperm must “swim,” to egg for

fertilzation to occur– No vascular tissue – must absorb water from

surface instead of absorbing from roots• Moss are commonly found in damp, shady

areas5.5.3

Division Bryophyta

5.5.3

Division Filicinophyta

• First group of vascular plants:– Evolved as a means to obtain all required

resources– Xylem and phloem transport resources

between distant organs:• Soil and roots provide minerals and water• Above ground provides light for leaves and

photosynthesis• Includes over 12,000 species of ferns

– Located in tropical and temperate forests5.5.3

Division Filicinophyta

5.5.3

Division Coniferophyta

• Includes ~ 550 species of large trees including pines, firs, spruces, and redwoods

• All produce seeds in cones• Most use wind pollination

for reproduction.• Almost all conifers are

evergreens• Most conifers have needles

– leaves modified to prevent water loss

5.5.3

Division Angiospermophyta

• Angion means “container,” – seeds are enclosed in fruits

• Includes ~ 235,000 species of flowering plants

• May rely on wind, birds, insects, and even mammals for pollination and reproduction.

5.5.3

Kingdom Animalia

• All organisms in Kingdom Animalia have the following characteristics:

– Eukaryotic

– Multicellular

– Heterotrophic

Phylum Porifera

• Includes sponges

• Characteristics: no body symmetry, no tissues, no organs; hermaphrodites; filter feeders; sessile

5.5.4

Phylum Cnidaria

• Includes corals, jellyfish, and sea anemone

• Characteristics: stinging cells for food and protection; two-way digestive tract; radial symmetry; drifters or sessile 5.5.4

Phylum Platyhelminthes

• Includes flatworms like planaria, flukes, and tapeworms.

• Characteristics: distinct head region (cephalization); bilateral symmetry; most are parasites; two-way digestive tract; no heart or lungs; flat shape - why?

5.5.4

Phylum Annelida

• Includes earthworms, marine worms, and leeches.

• Characteristics: segmented; well developed nervous, digestive, and circulatory systems; one-way digestive system.

5.5.4

Phylum Mollusca

• Includes snails, clams, octopus and squids.

• Characteristics: bilateral symmetry; one or more shells; soft bodies; most are aquatic

5.5.4

Phylum Arthropoda

• Includes insects, arachnids (spiders), and crustaceans

• Characteristics of all arthropods: exoskeleton made of chitin; jointed appendages; segmented body; open circulatory system

• Molting – process of shedding and exoskeleton and growing a new one to grow larger.

5.5.4

Insects

• The largest group of all animals (more than 1 million species)

• Characteristics: three body segments (head, thorax, and abdomen); six legs; live in water and land.

5.5.4

Crustaceans

• Include lobsters, shrimp, crayfish, crabs, and barnacles.

• Characteristics: aquatic; two body segments (cephalothorax and abdomen); gills

5.5.4

Arachnids

• Include spiders, scorpions, mites, horseshoe crabs, and ticks

• Characteristics: 2 body segments; eight legs; book lungs

5.5.4