5. Ecology and evolution

5.4 Classification

Some vocabulary

• Phylogeny: the evolutionary history of a group of organisms.

• Phylogenetic trees: formal hypotheses that identify likely relationships among species.

• Taxonomy: the identification and naming of species and their placement in a classification.

• Classification: an arrangement of organisms into hierarchical groups that reflect their relatedness

• Taxon: The organisms included within any category of the taxonomic hierarchy

The Binomial System of Nomenclature

• Carl von Linné (Carolus Linnaeus) invented a system in which species are assigned a two-part name, hence binomial.

• The first part identifies a group of species with similar morphology: genus

• The second part is the specific epithet or species• Ex.: Ursus maritimus (polar bear), Pan troglodyte

(chimpanzee), Homarus americanus (lobster).

Rules for binomial nomenclature

1. the first name is the genus name2. the genus name is always capitalized3. the second name is the species name4. the species name is not capitalized5. italics are used if the name is printed6. the name is underlined if handwritten

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Taxonomic Hierarchy

The taxonomic hierarchy Linnaeus defined is easily applied to Darwins

Arranges organisms into ever more inclusive categories or taxa. Largest to smallest:

• Kingdoms : Prokaryotae, Protoctista, Fungi, Plantae and Animalia.

• Phylum, Class, Order, Family, Genus, Species

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Kingdom

Phylum

Class

Order

Family

Genus

Species

AnimaliaChordataMammaliaCetaceaBalaenopteridaeBalaenopteramusculus

PlantaeConiferophytaPinopsidaPinalesTaxodiaceaeSequoiasempervirens

Blue Whale Coast Redwood

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Taxon

Taxon Grey wolf Date palm Truffle

Kingdom Animalia Plantae Fungi

Phylum Chordata Angiospermophyta Ascomycota

Class Mammalia Monocotyledoneae Pezizomycetes

Order Carnivora Palmales Pezizales

Family Canidae Arecaceae Tuberaceae

Genus Canis Phoenix Tuber

Species lupus dactylifera melanosporum

Traits of organisms as systematic characteristics

• Linnaeus focused on external anatomy. Ex.: a bird is a class of oviparous (egg-laying) animals, with feathered bodies, two wings, two feet, and a bony beak. No other animals possess all these characteristics.

• Two types of characteristics: morphological characters and behavioral characters

• Molecular differences also help classify different organisms with similar characters

Examples using simple external recognition features

• Plant classification:• Life cycle of a plant: male and female gametes

fuse together zygote develops into an embryo how embryo develops depends on the type of plant it is

• Four plant phyla:– Bryophyta – mosses, liveworts and hornworts– Coniferophyta – conifers– Filicinophyta – ferns– Angiospermophyta – flowering plants

AngiospermophytaEmbryo develops inside a seed *

Embryos develop into flowering plants with roots, stems and leaves

Flowers develop with ovaries and anthers

Egg cells develop in ovules enclosed inside ovary. Pollen develops in anthers

Male gametes transferred from flower to flower in pollen grains

Zygote formed by fusion of male and female gametes

ConiferophytaEmbryo develops inside a seed *

Embryos develop into conifers with roots, stems and leaves

Male and female cones develop

Egg cells develop in ovules on surface of scales in female cones. Pollen develops in anthers in male cones

Male gametes transferred from male to female cones in pollen grains

Zygote formed by fusion of male and female gametes

FilicinophytaEmbryo develops into a fern plant with stems, leaves and roots.

Fern produces spores inside sporangia *

Spores germinate and grow into prothalli (tiny, green plants)

Male and female gametes produced by prothalli

Male gamete swims to female gamete in another prothallus

Zygote formed by fusion of male anf female. Embryo initially fed by prothallus

BryophytaEmbryo develops into a sporophyte attached to a bryophyte plant

Sporophyte produces spores inside a sporangium *

Spores develop into bryophyte plant – no roots, but some have simple stems and leaves

Male and female gametes produced by bryophyte plant

Male gametes swim to female gamete

Zygote formed by fusion of male and female. Embryo fed by bryophyte

* Indicates dispersal stage

Examples using simple external recognition features

• Animal classification:• Life cycle of an animal: gametes fuse zygote

develops into an embryo blastula different systems form, such as skeletal, nervous, digestive, blood, etc.

• Animals are divided into over 30 phyla based on their characteristics

• Examples of 6 phyla

Phylum Mouth/anus

Sym-metry

Skeleton Other external recognition features

Porifera – Fan, cup, tube and glass sponges

No mouth or anus

None Internal spicules (skeletal needles)

Many pores over the surface through which water is drawn in for filter feeding. Very varied shapes

Cnidaria – hydras, jellyfish, corals, sea anemones

Mouth Radial Soft, but hard corals secrete CaCO3

Tentacles arranged in rings around the mouth with stinging cells. Polyps or medusae

Platyhelmintes – flatworms, flukes, tapeworms

Mouth only

Bilateral Soft, with no skeleton

Flat and thin bodies in the shape of a ribbon. No blood or gas exchange system.

Mollusca – bivalves, gastropods, snails, chitons, squid, octopus

Mouth and anus

Bilateral Most have shell made of CaCO3

A fold in the body wall called the mantle secretes the shell. A hard rasping radula is used for feeding

Annelida – marine bristleworms, oligochaetes, leeches

Mouth and anus

Bilateral Internal cavity with fluid under pressure

Bodies made up of many ring-shaped segments, often with bristles. Blood vessels often visible

Arthropoda – insects, arachnids, crustaceans, myriapods

Mouth and anus

Bilateral External skeleton made of plates of chitin

Segmented bodies and legs or other appendages with joints between sections.

Examples from six animal phyla

Arthropoda

• With jointed legs & segmented body.

• Have a hard exoskeleton made up of chitin.

• True champions of diversity & adaptation as they have conquered most habitat world wide.

• There are over a million species of arthropods worldwide.

• Eg.: insects, spiders, scorpions & crustacean like crabs & shrimps.

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Time to put you to the test!• From the following pictures:1. Study the organisms and assign each one to its phylum

2. List the organisms that are– A) bilaterally symmetric– B) radially symmetric– C) not symmetrical in their structure

3. List the organisms that have a) Jointed appendagesb) Stinging tentaclesc) Bristles

4. List the organisms that filter feed by pumping water through tubes inside their bodies.

Invertebrate diversity

Adocia cinerea

Alcyonium glomeratum

Nymphon gracilis

Pycnogonum littorale

Invertebrate diversity

Corynactis viridis

Cyanea capillata

Lepidonotus clava

Polymastia mammiliaris

Invertebrate diversity

Procedores littoralis

Arenicola marina

Loligo forbesii

Prostheceraeus vittatus

Caprella linearis

Gammarus locusta

Dichotomus key

It consists of a numbered series of pairs of descriptions to help assign a species to the correct group.

One description should clearly match the species and the other should clearly be wrong. They should be reliable and easily visible.

Each description leads either to another numbered pair in the key, or to an identification

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Dichotomus key, example

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Key to groups of marine mammals

1 Fore and hind limbs visible, can emerge on land……………………………………………………………….. 2Only fore limbs visible, cannot live on land....... 6

2 Fore and hind legs have paws ……………………….. 3Fore and hind limbs have flippers …………………. 4

3 Fur is dark ………………………………………… sea ottersFur is white ……………………………….…… polar bears

4 External ear flap visible .… sea lions and fur sealsNo external ear flap ………………………………………. 5

5 Two long tusks ……………………………….….. walrusesNo tusks ………………………………………….… true seals

6 Mouth breathing, no blow hole ……………… ……… … …………………………………. dugongs and manateesBreathing through blowholes ……………………….. 7

7 Two blow holes, no teeth ……….... baleen whalesOne blowhole, teeth …….. Dolphins, porpoises and whales

Dichotomos keys, homework

• Apply and design a key for the ten organisms in your handout based on their footprints.