Classification

Taxonomy and EvolutionTaxonomy – (a branch of Biology) involves the

identification, naming, and

classification of species• To reduce confusion in discussing organisms• Trying to make sense of the environment• Showing evolutionary Links• Predicting characteristics shared by members of

a group• One goal of taxonomy is to assign a universal

scientific name to each known species

The Linnaean System of Classification

• Most widely used• Developed by botanist Carolus Linnaeus (1707-1778)

The Linnaean System of Classification

Two Main Characteristics

1. A two part Latin name for each species and a hierarchy, or ordering, of species into broader and broader groups

Binomial – Linnaean System assigns a 2-part name, to

each species

1st Part – the genus the species belongs

2nd Part – one species within the genus

2. The system groups species into broader categories; starting with genus in the binomial

• Closely related species are grouped into the same genus

The Linnaean System of Classification• The first name in the binomial nomenclature system is

always capitalized and it refers to the genus • The second name always begins with a small letter and

refers to the species• Both are always written in italics when typed or

underlined when written by hand. • Most words are Latin or Greek in origin

Genus

Species

The Linnaean System of Classification

• Early classification organisms were placed into 2 groups:• Plants• Animals

• As more organisms were discovered as well as the invention of the microscope early system had to be modified.

The Linnaean System of Classification

Five Kingdoms• Most widely accepted system

• Kingdom Plantae – plants (cactus to moss)• Kingdom Animalia – animals• Kingdom Fungi – Fungi and mold• Kingdom Protoctista – protozoa and algae• Kingdom Prokaryotae – the bacteria

The Linnaean System of Classification

Seven Taxa• System was established because of the

hundreds of thousands of different plant and animals:• Kingdom• Phylum• Class• Order• Family• Genus• Species

Other Classification

• Feeding Habits: CarnivoreHerbivore• Habitat: Land dwelling / Aquatic• Daily activity: Nocturnal/Diurnal (active in the day time)• Risk: harmless/venomous• Anatomy: vertebrates/invertebrates

Depending on the reason there is no right or wrong way to classify as long as you are consistent

Some Plant Phyla

4 Phyla Most Familiar:1. Bryophyta – includes plants of very short

stature (moss)

2. Filicinophyta – Ferns and Horse tails

3. Coniferophyta – Conifer phylum (cedar & pine trees)

4. Angiospermophyta – include all flowering plants which have their seeds surrounded by fruit

Plant Characteristics

Vegetative Characteristics• Bryophytes are non-vascular because they

do not have a true vascular system

Xylem Tissue – transports water and

nutrients up from the roots

Phloem Tissue – transports water and

nutrients from the leaves

towards the stem and roots

Plant Characteristics

• Conifers can be recognized by woody stems and leaves in the form of needles or scales

• Angiosperms are recognized by their flower and seeds in their fruit

Reproductive Characteristics

• Bryophytes do not produce flowers or seeds• They produce spores

• Microscopic reproductive devises • Spores are transported by rainwater and

humidity• This is why they are found in damp habitats

• Angiosperms rely on birds, insects, and mammals to transport pollen• The sexual reproductive organ of

angiosperms is the flower

Some Animal Phyla

Six Invertebrate Animal Phyla

1. Porifera• Sponges – very simple marine animals

• Sessile – stuck in place• They do not have mouths or digestive tracts

• They feed by pumping water through their tissues to filter out food

• No muscle or nerve tissue or distinct internal organs

Some Animal Phyla

2. Cnidarians• Corals, sea anemones, jellyfish, hydra, floating colonies

(Portuguese man-of-war)• Nematocysts – stinging cells

• One characteristics common to all in this group• Some are sessile others are fee – swimming or float

using currents• Catch food with their tentacles and they have a gastric

pouch with one opening

Some Animal Phyla3. Platyhelminthes• Flatworms

• They have only one body cavity• A gut with one opening for food to enter and

waste to exit• No heart or lungs

Tapeworm

Some Animal Phyla4. Annelida• Segmented worms

• Earthworms, leeches, and polychaetes• Bodies are divided up into segments separated by rings• They have bristles on their bodies (not always visible)• They have a gastric tract where they have a mouth on

one end and intestines and an opening on the other end where waste are released

polychaetes

Some Animal Phyla5. Mollusca• Most are aquatic

• Snails, clams, and octopuses• Produce shells using calcium• Bodies are not segmented

6. Arthopoda• Have a hard exoskeleton made with chitin, segmented

bodies, and limbs that are jointed• Limbs can be used for walking, swimming, are eating

• Spiders, insects, scorpions, and crustaceans (crabs & shrimp)

• Over a million different species all over the world

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• 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 – a phylogenetic diagram that specifies the

derived characteristics of clades

Using A Dichotomous Key

1. You look at the first section of the key which has a pair of sentences describing a characteristic

2. Next, you look at the organism to see if the particular characteristic described in the first line is present in the organism

3. If the answer is yes, then go to the end of its line and find the number of the next pair of statements to look at, follow the number given and continue until the end

4. Keep going until the end of the line has a name instead of a number

• If you have answered each question correctly, that will be the name of your organism

Using A Dichotomous Key