syllabus theme b plant classification & diversity ... · syllabus theme b plant classification...
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SYLLABUS THEME BPLANT CLASSIFICATION
& DIVERSITY
B1: Naming and classification of organisms
Biology of Plants - Raven et al. 2005pp. 219-237
INTRODUCTION TO TAXONOMY
TaxonomyNamingDescribingClassifying
ClassificationGrouping organisms by their similarities or relationships
SystematicsAnalytical study of the diversity and relationships of organisms
HISTORICAL DEVELOPMENT
Theophrastus – 4th Century• 500 plants based on leaf characteristics
13th Century – Monocots / Dicots based on stem structure18th Century – flower and fruit structures used in classification
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NAMING OF ORGANISMS
Why we use Latin names to name living organisms?
Facilitates international science
Initially – short phrase, polynomialMentha (genus name)
Mentha floribus spicatis, foliis oblongis serrattis(phrase name)
NAMING OF ORGANISMS
Swedish Scientist –Carolus Linnaeus (1707-1778)Binomial system of NomenclatureA plant is named according to the International Code of Botanical Nomenclature (I.C.B.N.)
Phaseolus vulgaris L.
Genus- Capital letter
Specific epithet- Small letter- Never stands alone
name consists of 2 parts (binomial): a generic name + a specific epithet
Authority- Abbreviation of the person who first published the name
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I.C.B.N. & PLANT NAMESplant nomenclature is independant of zoological nomenclature;the rules of the code are retrospective;the names are published in Latin, irrespective of its origin;the nomenclature of any taxon is based on the priority of publishing;every taxon can have only one correct name & it is the oldest name according to the rules;the application of botanical names is determined by means of nomenclatural types (typification).
TAXONOMIC RANKING
Taxon – Group of organisms of which all members share certain common characteristicsThe aim of a taxonomic ranking (hierarchy) is to arrange the taxa in such a way to reflect at best the differences and similarities amongst themEach taxonomic level is more general than the one below it
CATEGORY NAME OF TAXON
DESCRIPTION
Kingdom Plantae Multicellular eukaryotic organisms, photosynthetic
Phylum Anthophyta Flowering plants with ovules born in a closed ovary
Class Monocotyledones Embryo with one cotyledon, flowers trimerous
Order Commelinales Reduced flower parts, elongated leaves and dry 1-seeded fruits
Family Poaceae Grass family. Reduced green flowers in spikelet. Fruit is a caryopsis (grain)
Genus Zea Tall annual grass with separate female and male flowers
Species Zea mays Only one species in genus - maize
HIERARCHICAL CLASSIFICATION
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B3: Kingdom Plantae
THE FIVE KINGDOM SYSTEM
Robert Whittaker
Plantae Fungi Animalia
Protista
Monera
Eukaryo
tes
Prokaryotes
THE THREE DOMAIN SYSTEM
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APICAL MERISTEMS
Apicalmeristem
Developingleaves
100 µm
Apical meristem
Root 100 µmShoot
gametophyteMitosis Mitosis
Gametes
Zygote
sporophyte
MEIOSIS FERTILIZATION
2n2n
n
nnn
nSpores
Mitosis
ALTERNATION OF
GENERATIONS
FIVE KEY CHARACTERISTICS IN LAND PLANTS
WALLED SPORES PRODUCED IN SPORANGIA
MULTICELLULAR GAMETANGIA
MULTICELLULARDEPENDENT EMBRYOS
SporesSporangium
SporophyteGametophyte
Sporophyte and sporangium of Sphagnum (a moss)
Female gametophyteArchegoniumwith egg
Antheridiumwith sperm
Malegametophyte
Archegonia and antheridia of Marchantia (a liverwort)
EmbryoMaternal tissue
2 µm
Wall ingrowthsPlacental transfer cell
10 µm
Embryo of Marchantia
THE GROUPS OF PLANTS
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Ovule is borne naked
GymnospermsNaked seeds
Eg. pine, cycads
Ovule is enclosed in ovary
AngiospermsEnclosed seed
Eg. Proteaceae, Fabaceae
Seed plants
A specimen of Welwitschia mirabilis living in Namib Desert, Namibia – survives on fog
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ANGIOSPERM CHARACTERISTICS
Vascular plantsProduce flowers and seeds enclosed in a fruitLife cycle:
Sporophyte is dominantGametophytes are reduced and dependant on the sporophyte
ANGIOSPERM CHARACTERISTICS
Heterosporous - having two types of sporesMicrospores – pollen grain
Megaspore – embryo sac
Double fertilization2n zygote
3n endosperm
DICOTS VS MONOCOTS