5.3 Classification

Classification For centuries, humans have been attempting to classify the various species on Earth in order to learn more about the species and their evolutionary history. Classification attempts to group more related species together

Binomial System of Nomenclature A “2 name” naming system that was designed by Carolus Linneaus in the 18th century. Every species has a Latin name, The first part of the name is the name of the genus, the second part is the species. The name is printed in italics If hand written, underline the name The first letter of the genus is capitalized The first letter of the species is not

Examples: Humans: Homo sapiens GENUS SPECIES Dogs: Canis lupus familiaries SUBSPECIES

Linnaeus’ system was largely based on morphology and is not the best way to classify organisms (Modern methods use evolutionary relationships to classify organisms) However, Linnaeus’ system is still the basis of how we name organisms today.

International Cooperation & Classification Scientists all around the world use the binomial system as a universal naming system to identify a species rather than the many local names

Hierarchy of Taxa Taxonomists classify species using a hierarchy of taxa TAXON = group of something Taxon (singular), taxa (plural) The taxa form a hierarchy, as each taxon includes taxa from the level bellow

Three Domains Traditional classification systems have recognized 2 major categories of organisms based on cell types: eukaryotes and prokaryotes Think back to Topic 1 in grade 11. Do you remember the difference?

Three Domains Because prokaryotes are so diverse, most classifications systems recognize 3 major categories or domains Eubacteria (bacteria) Types of Archaea (archaeans) prokaryotes Eukaryota (eukaryotes)

Histones Associated with DNA BACTERIA ARCHAEA EUKARYOTA absent Proteins similar to histones bound to DNA Present

Presence of Introns BACTERIA ARCHAEA EUKARYOTA Rare or absent Present in some genes Frequent

Structure of Cell Walls BACTERIA ARCHAEA EUKARYOTA Made of chemical peptidoglycan Not made of peptidoglycan Not made of peptidoglycan, not always present

Cell Membrane Difference BACTERIA ARCHAEA EUKARYOTA Glycerol-ester lipids; Unbranched side chains; D-form of glycerol Glycerol-ether lipids; L-form of glycerol

Archaeans Found in a broad range of habitats: Ocean surface deep ocean sediments oil deposits below the Earth’s surface High salt concentrations High temperatures Ex: methanogens which live in the intestines of cattle and produce methane as a waste product.

Hierarchy of Classification for Eukaryotes Seven level hierarchy of taxa to classify organisms Kingdom Phylum Class Order Family Genus Species

Kingdoms Kingdoms are the broadest category Originally there were only 2 Kingdoms: Plants and Animals Today, we have identified 5

Modern Kingdoms Kingdom Plantae (plants) Kingdom Animalia (animals) Kingdom Fungi (fungi and moulds) Kingdom Protoctista (protozoa and algae – includes paramicium and amoebas) Kingdom Prokaryotae (bacteria)

Examples of Classification You need to know an example of 1 plant and 1 animals species from domain to species level See page 262 for an example of the grey wolf and the date palm

Ex: Humans KINGDOM Anamalia PHYLUM Chordata CLASS Mammalia ORDER Prima FAMILY Hominidae GENUS Homo SPECIES sapiens

Ex: Garden Pea KINGDOM Plantae PHYLUM Angiospermae CLASS Dicotyledoneae ORDER Rosales FAMILY Papilionaceae GENUS Pisum SPECIES sativum

Natural Classification The genus and accompanying higher taxa consist of all the species that have evolved from one common ancestor Because of the common ancestor we can expect the members of a natural group to share many characteristics

Natural vs Artificial Characteristics Plants and fungi were one time classified together because they both have cell walls, but this is an artificial classification as their cell walls evolved separately and molecular research shows they are no more similar to each other than to animals.

Natural vs Artificial Characteristics Ex: wings of insects, birds, and bats We will come back to this when we talk about convergent evolution and analogous traits.

Reviewing Classification Sometimes taxonomists reclassify species when new evidence shows that a previous taxon contains species that have evolved from different ancestral species The new evidence is usually DNA sequencing

Advantages of Natural Classification Natural classifications help in identification of species and allow the prediction of characteristics shared by species within a group

Plants All plants are found in a single kingdom During the life cycle of a plant, male and female gametes develop and fuse to form a zygote, which will develop into an embryo and then the particular plant

Expectation, page 266 Distinguish between the following phyla of plants using simple external recognition features Phyla: bryophyte ,filicinophyta, coniferophyta, angiospermophyta

Bryophyta Mosses and liverworts Small terrestrial plants that do not have true roots, stems or leaves (but may have similar structures) Leaf-like structures arranged in a spiral Usually live in clusters

Filicinophyta Ferns Have true leaves New leaves unroll Have an underground creeping stem (called a rhizome)

Coniferophyta Conifers Woody plants, with a single wooden trunk and side branches Leaves are long thin needles and dark green Produce seeds in cones

Angiospermophyta Angiosperms/ Flowering Plants Have flowers Seeds are in ovaries with become the fruit Leaves usually as a leaf blade and a leaf stalk, with veins visible on the lower surface

Animal Phyla Animals are divided into over 30 phyla Distinguish between the following phyla of animals, using simple external recognition features. (see page 267)

Porifera Sponges Most primitive animals with a simple body Live in water Do not move around No mouth, but have small holes through which water is pumped into body and have be filtered for food before pumping out

Cnidaria Jellyfish and sea anemones Have stinging cells Radially symmetrical Have a gastro-vascular cavity (a hollow space in the centre of the body) with only one opening to the cavity Often have tentacles around the opening

Plathyelminthes Flatworms Soft flattened body with a definite head region Bilateral symmetry Gastro-vascular cavity Usually one opening to cavity Live in water or damp environments Can be free-living or parasitic

Arthropoda Animals with jointed legs Ex: insects, arachnids, crustaceans Exoskeleton made of chitin (a polysaccharide) Segmented body Appendages to each segment At least 3 pairs of legs May be free living or parasitic

Annelida Worms and leeches Bodies of ring-like segments Have a mouth and an anus Live in water or moist soil May be free living or parasitic No legs Bristles from body which help them move

Mollusca Snails, squids, clams, slugs Soft unsegmented bodies May have a shell

Chordates - Vertebrates All are vertebrates because they have a backbone composed of vertebrae There are 5 major classes of chordates You need to recognise the features of birds, mammals, amphibians, reptiles, and fish (page 268)

Birds Skin with feathers made of keratin 2 legs, 2 wings Females lays eggs with shells Maintain constant body temp

Mammals Skin with follicles with hair made of keratin Lungs with alveoli, ventilated used ribs and diaphragm Give birth to live young and all feed young with milk from mammary glands Maintain constant body temperature

Amphibians Soft moist skins permeable to water and gases Simple lungs with small folds and moist skin for gas exchange 4 legs as an adult Larval stages lives in water and as an adult usually lives on land Do not maintain constant body temp

Reptiles Impermeable skin covered in scales of keratin Lungs with extensive folding to increase the surface area Female lays eggs with soft shells Do not maintain constant body temp

Fish Scales with are bony plates in the skin Gills No limbs Remain in water throughout their life cycle Do not maintain constant body temp

Dichotomous Keys Apply and design a key for a group of up to eight organisms. Keys are most commonly used to identify plants, insects, and birds. You need to be able to construct a dichotomous key page 265