Systematics of Living Organisms Notes PDF

MITHIBAI COLLEGE BIOLOGY DEPARTMENT Chapter 2 : SYSTEMATICS OF LIVING ORGANISMS Systematics: It is the study of kinds and diversity of organisms and their comparative and evol...

MITHIBAI COLLEGE BIOLOGY DEPARTMENT Chapter 2 : SYSTEMATICS OF LIVING ORGANISMS Systematics: It is the study of kinds and diversity of organisms and their comparative and evolutionary relationship. Taxonomy: It is the classification following certain rules or principles. Classification: It is the arrangement of organisms or groups in distinct categories in accordance with a particular and well established plan. Three Domains of life: It was proposed by Carl Woose in 1990. All the three domains have unique rRNA structure. A category in classification is a rank involved in the hierarchy of steps. Chemotaxonomy: considers characteristics of compunds present in the Branches of taxonomy organisms. Eg. Cell wall composition of different organisms Numerical taxonomy: it evaluates resemblances and differences based on large number of characters obtained from all disciplines of biology. Cladogram: a typical branching pattern showing hypothetical reationship denoting a comparison of organisms and their common ancestors. Phylogeny: Takes into consideration the morphological features and also the relationship of one group of organism with other groups of life. DNA barcoding: it is a new method for identification of any species based on its DNA sequence from a tiny tissue sample of the organism under study. A horse and an ass are considered as two different species because they cannot interbreed under natural conditions to produce fertile offspring. 1 MITHIBAI COLLEGE BIOLOGY DEPARTMENT Rules of Binomial Nomenclature:  it contains two words – Genus (first word) Importance of binomial nomenclature over and species (second) vernacular names:  generic name is a noun and begins with a 1. One organism can have many capital alphabet. different names in different languages which creates  Specific name is a descriptive adjective and confusion. begins with a small letter. 2. Binomial nomenclature system is  If handwritten, the name should be easy and simple. underlined and if typed it should be in 3. Does not change from place to place thus creates uniformity. italics.  The generic and specific name should have 3 to 13 letters each. Binomial system of Nomenclature  Usually the name of the author who names was proposed by Carl Linnaeus. a plant or animal is also written in full or abbreviated form after scientific name. Eg. Mangifera indica L. L stands for Linnaeus. 2 MITHIBAI COLLEGE BIOLOGY DEPARTMENT Five kingdom classification was proposed by R.H Whittaker SALIENT FEATURES OF FIVE KINGDOMS: 1. Kingdom Monera:  Membrane bound cell organelles (chloroplast, mitochondria, ER etc.) absent.  Ribosomes are 70S type.  Mode of reproduction – asexual or binary fission or budding. Rarely sexual (conjugation method).  Types of bacteria on basis of shape: Spherical (coccus), rod like (bacillus), comma shaped (vibrio), Spiral (spirillum).  Types of bacteria on basis of evolution – Archebacteria and Eubacteria. Archebacteria: These are found in extreme/harsh environments (extremophiles) like saline areas (halophiles) or hot springs with very high temperatures (thermophiles). Methanogenic bacteria found in the gut of ruminant animals like cows and buffaloes produce methane which is used in biogas plants. Eubacteria: These are true bacteria with cell wall made of peptidoglycan. They may be autotrophs or heterotrophs. Autotrophs may be photosynthetic (eg. Chlorobium, Chromatium) or chemosynthetic (eg. Sulphur bacteria) Heterotrophs are more abundant and are mostly filamentous, help in nitrogen fixation and act as decomposers. Eg. Cyanobacteria like Nostoc Useful and harmful bacteria: i. Lactobacilli – curdling of milk. ii. Azotobacter – nitrogen fixation iii. Streptomyces – antibiotic production iv. Pathogenic bacteria cause diseases like typhoid, cholera, tuberculosis, tetanus. Mycoplasma: these are smallest living organisms without cell wall and hence are resistant to antibiotics (pathogenic). 2. Kingdom Protista:  It forms the connecting link between unicellular Kingdom Monera and all eukaryotic Kingdoms Plantae, Fungi and Animalia. a) Plant like Protists (Chrysophytes / Phytoplanktons)  These are photosynthetic and are also major producers in oceans.  Diatoms – cell wall is present and is made of silica. Body wall is made of two soap box like fitting covers.  Left over shells over the years form granular “Diatomaceous earth” used in polishing and filtration`. 3 MITHIBAI COLLEGE BIOLOGY DEPARTMENT b) Animal like Protists (protozoans)  Lack cell wall. Type of protozoan Example Diseased caused if any Amoeboid protozoan Amoeba ----- (pseudopodia is locomotary organ) Entamoeba Amoebic dysentery Flagellated protozoan Trypanosoma Sleeping sickness Ciliated protozoan Paramoecium ----- Sporozoan protozoa Plasmodium Malaria c) Dinoflagellates  Mostly marine and photosynthetic  Cell wall made of stiff cellulosic plates  Gonyaulax – famous for causing ‘Red Tides’ which makes the sea appear red. d) Fungi like protists  Saprophytic – found on decaying leaves  Cells aggregate to form plasmodium which produces spores that can survive in harsh conditions. e) Euglenoids  Lack cell wall but have a tough covering called pellicle made of protein.  In presence of light behaves like an autotroph and in absence of light is heterotrophic.  Contain photosynthetic pigments similar to higher plants. 3. Kingdom Plantae:  Mostly autotrophs, very few are semi autotrophic insectivorous plants like Venus Fly trap, pitcher plant, bladder wort, etc or heterotrophic parasites like Cuscuta.  Kingdom Plantae is divided into Cryptogams and Phanerogams. 4. Kingdom Fungi:  Fungal body is called mycelium made of many hyphae.  Hyphae may be septate or aseptate.  Multinucleate coenocytic hyphae (hphae without septa thus showing one cell with many nuclei) are commonly present.  Cell wall made of chitin or fungal cellulose. 4 MITHIBAI COLLEGE BIOLOGY DEPARTMENT  Reproduction may be sexual or asexual (fragmentation, fission, or budding)  These show heterotrophic mode of nutrition with extracellular digestion since they are dependent on dead and decaying organic matter for food. Some are parasitic or predators. Some live as symbionts (in lichens) or as mycorrhiza (in roots of higher plants). NOTE ON USEFUL & HARMFUL FUNGI  As food – mushroom, morels, truffles  In baking and brewing industry – Saccharomyces (yeast)  Antibiotic production – Penicillium  In research – Neurospora  Disease causing: Albugo (Parasite on Mustard), Puccinia (Rusts), Ustilago (Smuts) CLASSIFICATION OF FUNGI Kingdom Fungi sexual sexual reproduction not reproduction known known Deuteromycetes mycelium aseptate and mycelium septate (Imperfect Fungi) coenocytic Phycomycetes Ascomycetes Basidiomycetes Eg. Alternaria (Algal Fungi) (Sac Fungi) (Club Fungi) Eg. Rhizopus, Eg. Penicillium, Neurosopra, Eg. Agaricus, Mucor, Sacharomyces, Ustilago, Puccinia Albugo Morels, Truffles 5 MITHIBAI COLLEGE BIOLOGY DEPARTMENT 5. Kingdom Animalia  These are heterotrophs with holozoic mode of nutrition.  Most of them have the capacity of locomotion.  These are multicellular eukaryotes which lack chlorophyll and cell wall but show definite growth. Differences between Kindom Plantae and Kingdom Animalia Kingdom Plantae Kingdom Animalia 1. Cell wall present 1. Cell wall absent 2. Plastids are present 2. Plastids absent 3. Autotrophic mode of nutrition 3. Heterotrophic (holozoic or parasitic) mode of nutrition 4. Indefinite growth 4. Definite growth 5. Do not show locomotion 5. Have the capacity to locomote (except Sponges) Viruses:  These are obligate parasites (need a host to complete its life cycle).  They lack their own cell machinery.  They have a protein c oat (capsid) around nucleic acid strand and hence are considered to be acellular organisms.  Viruses are called as infectious nucleoproteins – because – they are inactive outside a host cell. But once they enter their specific host cell they take charge of cellular machinery of host cell and duplicate themselves.  The genetic material in viruses can be single or double stranded DNA or RNA.  Viruses that infect bacterial cell are called bacteriophages which normally have double stranded DNA. Plant Diseases caused by Viruses Animal Diseases caused by Viruses Leaf curling, yellowing, mosaic Foot and mouth disease, Small pox, formation mumps, herpes, common cold, AIDS, CoVID 6 MITHIBAI COLLEGE BIOLOGY DEPARTMENT Viroids:  These are low molecular weight RNA which lack protein coat and are smaller in size than viruses.  Potato spindle tuber disease was found to be caused by viroids. Differences between viruses and viroids Viruses Viroids 1. The genetic material is enclosed 1. Protein coat is absent inside capsid (a protein coat) 2. These are bigger in size than the 2. These are smaller in size than the viroids viruses 3. Genetic material may be either DNA 3. Genetic material is always RNA. or RNA Lichens:  Lichen is a co-existence of an algae (a phycobiont) and a fungus (a mycobiont) thus living in a symbiotic association.  The algae provide food to the fungus and in return the fungus provides shelter, absorbed water and minerals to the algae.  Lichens are found in extreme environments like snow clad poles but are sensitive to pollution. They are not found in polluted regions and hence are considered as pollution indicators. 7