Earnst Mayr has been called as "The Darwin of 20h century"He worked on Taxonomy, Zoogeography,Evolution,Systematics and History & Philosophy of biology. He gave the biological concept of species.
The number of species that are known and described ranges between 1.7-1.8 million
ICBN-Intenational Code of Botanical Nomenclature
ICZN-International Code of Zoological Nomenclature
Each biological name is made up of two components, generic name and specific epithet. This system is calledas bionomial system.
Biological names are generally in Latin and written in italics. They are latinised or derived from Latin irresepectiveto their origin.
Both the words in a biological name, when handwritten, are separately underlined, or printed iri italics to indicatetheir Latin origin.
Classification is the process by which any thing is grouped into convenient categories based on some easilyobservable characters.
The group included in taxonomic categories is called as taxon.
Characterisation, identification, nomenclature and classification are the processes that are basic to taxonomy.
Category is a part of overall taxonomic arrangement and all categories together constitute the taxonomic hierarchy.
As we go higher from species to kingdom the number of common characteristics goes on decreasing.
Herbarium is a store house of collected plant specimens that are dried, pressed and preserved on sheets.
Keys : The keys are based on the contrasting characters generally in a pair called couplet. Each statementin the key is called a lead.
Keys are generally analytical in nature.
Flora:It contains the actual account of habitat and distribution of plants of a given area. These provide theindex to the plant species found in a particular area.
Monograph : It contains complete informations on any one taxon.
CHAPTER-II:BIOLOGICAL CLASSIFICATION
Aristotle was the earliest to attempt a more scientific basis for classification.
Aristotle divided animals into two groups (1) Having red blood cells and (2) Do not having red blood cells.
R.H. Whittaker's Classification is phylogenetic classification.
Archaebacteria differ from other bacteria in having a different cell wall sturcture and this feature is responsiblefor their survival in extreme conditions.
Some cyanobacteria can fix atmospheric N2 in their specialised cells called heterocysts. eg.Nostoc& Anabaena.
In diatoms the cell walls form two thin overlapping shells, which fit together as in a soap box.
The cell wall of diatoms (chrysophytes) are embedded with silica and thus the walls are indestructible.
Red dinoflagellates undergo very rapid multiplication so they make the sea appear red, called as red tides.
The cell wall of fungi is composed of chitin and polysaccharides.
Some fungi can live as symbionts in association with algae (lichen) and with roots of higher plants as mycorrhiza.
In fungi the sexual cycle involves.
(1)Plasmogamy
(2)Karyogamy
(3) Meiosis.
Phycomycetes are found in aquatic habitats,on decaying wood on moist or damp places or as obligate parasiteson plants.
In ascomycetes and basidiomycetes dikaryotic (n + n, two nuclei per cell) condition is also found called as dikaryophase.
Many members of ascomycetes like morels and buffles are edible fungi.
Members of basidiomycetes are mushrooms, bracket fungi and puffballs.They produce basidiospores exogenouslyon their basidium (pl. basidia). Some times basidia are arranged in fruiting bodies called basidiocarp.
Deuteromycetes:they are commonly known as imperfect fungi because they reproduce only by asexual orvegetative reproduction, not by sexual reproduction. They produce septate and branched mycelium.Somemembers are saprophytes or parasites while a large number of them are decomposers of litter and help inmineral cycling.
CHAPTER-III:PLANT KINDGOM
Kingdom plantae includes all eukaryotic chlorophyllous autotrophic organisms. A few members are partiallyheterotrophic such as insectivorous plants or parasites. Bladderwort and venus fly trap are examples ofinsectivorous plants and Cuscuta is a parasite.
The artificial system gives equal weightage to vagetative and sexual characteristics, this is not acceptablesince thevegetative characters are more easily effected by envirnoment.
Natural classification is based on natural affinities among the organisms and consider not only the extemalfeatures but also internal features.
The phylogenetic systems are based on evolutionary relationships between the various organisms.
Numerical taxonomy is based on all observable characters. Number and codes are given to all the charactersand these data are made and processed by the help of computer for making the numerical taxonomy.
Cytotaxonomy : cytotaxonomy is based on cytological informations like chromosome number, structure andbehaviour.
Chemotaxonomy : Chemotaxonomy uses the chemical constituents of the plant.
ALGAE
Algae are highly variable in form and size, they are unicellular (microscopic), colonial, filamentous, and also formmassive plant bodies (kelps)
Isogamy:Fusion of similargametes in size is isogamy.These gametes maybe motile (Ulothrix) ornonmotile (Spirogyra).
Anisogamy :Fusion of two gametes dissimilar in size is anisogamy eg. some species of Chlamydomonas.
Oogamy : Fusion between one large, nonmotile (static) female gamete and a smaller, motile male gamete istermed as Oogamy. eg. Volvox, Fucus.
At least a half of the total CO, fixation on earth is carried out by algae through photosynthesis.
Many species of Porphyra, Laminaria and Sargassum are among the 70 species of marine algae usedas food.
Many algal products like algin (from brown algae) and carrageen (red algae) are used commercially.Agar-agar(from Gelidium and Gracillaria) are used to grow microbes and preparation of ice creams and jellies.
Chlorella and Spirullina are unicellular algae, rich in proteins and are used as food supplements even byspace travellers.
CHLOROPHYCEAE (Green algae)
Most of the members of chlorophyceae have one or more storage bodies called pyrenoids located in chloroplasts.Pyrenoids contain protein besides starch.
In green algae the cell wall is made of inner layer of cellulose and an outer layer of pectose.
PHAEOPHYCEAE:(Brown algae)
The members of brown algae show great variation in size andform.They range from simple branched, filamentousforms to profuselybranched form, which may reach a height of 100 meters.
Their cellulosic cell wall is covered on outside by a gelatinous coating of algin.
Food is stored in them as complex carbohydrate, laminarin or mannitol.
The gametes of these algae are pyriform (pear shaped) and bear two laterally attached flagella.
Common members of phaeophyceae are - Ectocarpus, Dictyota, Laminaria, Sargassum & Fucus.
RHODOPHYCEAE(Red algae)
Majority of red algae are found in marine water with greater concentrations in warmer areas.The reserve food in red algae is floridean starch which is very similar to amylopectin and glycogen.Sexual reproduction in red algae is Oogamous and accompanied by complex post fertilisation developments.
Examples of red algae are Polysiphonia, Porphyra, Gracillaria, Gelidium.
BRYOPHYTA
Bryophytes lack true roots, stem or leaves. They may possess root like, stem like or leaf like structures.
Main body of bryophytes is made of haploids cells and it produces gametes hence is called as gametophyte.
Sporophyte in them is not free living, but attached to the photosynthetic gametophyte and derives nourishmentfrom it.
Sphagnum provides peat that have long been used as fuel and also used as packing material for trans-shipmentof living material because of its high water holding capacity.
Mosses along with lichens are the first organisms to colonies rocks and hence are of great ecological importance.Mosses form dense mats on the soil, they reduce the impact of falling rain and prevent soil erosion.
LIVER WORTS:
The plant body of liver wort is thalloid and the thallus is dorsiventral and closely appressed to the substratum.The leafy members of liverworts have tiny leaf like appendages in two rows on the stem like structures.
Asexual reproduction in liverworts takes place by fragmentation of thalli or by the formation of specialised structurescalled gemmae (gemma-singular). Gemmae are green multicellular, asexual buds, which develop in smallreceptacles called gemma cups.
The sporphyte is differentiated into a Foot, Seta and Capsule (Marchantia). After meiosis spores are producedwithin the capsule.
MOSS
The gametophyte body of moss is made up of two stages.
(i) Protonema-first stage produced from spore.
(ii)Leafy stage - The second stage produced from buds of protonema.
Vegetative reproduction in mosses is by fragmentation and budding in;the secondary protonema.
Common example of mosses are Funaria, Polytrichum and Sphagnum.
PTERIDOPHYTA
In pteridophytes the main plant body is sporophyte which is differentiated into root, stem & leaves. They havewell differentiated vascular tissues.
The leaves in pteridophyta are small (microphylls) as in Selaginella or large (macrophylls) as in ferns.
Only few genera of pteridophytes show heterospory; they produce two types of spores, Macrospores (large)and Microspores(small).
In heterosporous pteridophytes the female gametophytes are retained on the parent sporophyte for variableperiod.The development of zygote into young embryo takes place within the female gametophytes. This isprecursor to the seed habit, considered as an important step in evolution.
GYMNOSPERMS
In gymnosperms ovules are not enclosed in ovary walls and remain exposed both before and after fertilisation,so they produce naked seeds.
Gymnosperms are medium sized trees or tall trees and shrubs.
The giant redwood tree Sequoia is one of the tallest tree species.
In gymnospemrs the stem may be unbranched (Cycas) or branched (Pinus. Cedrus).
The leaves may be simple or pinnately compound.
The leaves in gymnosperms are well adapted to withstand extremes of temperature, humidity and wind.In conifers,the needle like leaves reduce the surface area. Their thick cuticle and sunken stomata also help to reduce waterloss. These are the xerophytic characters in gymnosperms.
The male and female cones (strobili) may be produced on the same tree (Pinus) or on different trees(Cycas)
In Gymnosperms the male and female gametophytes do not have an independent free living existence.
Lichens:
Lichens are symbiotic associations between algae and fungi.
The algal component of lichen is known as phycobiont and fungal component is known as mycobiont.
Algal component-Autotrophic
Fungal component-Heterotrophic
In lichens algae prepare food for fungi and fungi provide shelter and absorb mineral nutrients and water foralgae.
Lichens are very good pollution indicators, they do not grow in polluted areas.
Most of the lichens are ascolichen (on the basis of fungal component).
Most common phycobiont in Lichens :-Trebouxia
Parmelia species are used as a curry powder in India.
Cetaria islandica is used as laxative.
Cladonia rangiferina is commonly known as reindeer moss.
Viruses:
The viruses are non-cellular organisms that are characterised by having an inert crystalline structure outsidethe living cell.
The name virus that means venom or poisonous fluid was given by Pasteur.
Viruses are obligate parasite.
Viruses are inert outside their specific host cell.
In addition to proteins viruses also contain genetic material that could be either RNA or DNA.
Generally, plant viruses are single stranded RNA viruses.
Bacteriophages are generally double stranded DNA viruses.
The protein coat of virus is called Capsid made of small subunits called capsomeres. These capsomeres arearranged in helical or polyhedral geometric forms.
Viroids:
Discoverer-T.O.Diener
They have only low molecular weight RNA, no protein coat.
Potato spindle tuber disease is caused by potato spindle tuber viroid.
Note:Viruses,Viroid and Lichens are not included in five kingdom system of classification.
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