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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.