CHAPTER 2 NOTES (PART 1)

SYSTEMATICS  

 

The systematic arrangement of organisms into groups and sub groups on the basis of their similarities and dissimilarities is called classification.

    Need for Classification:

i) There are millions of different kinds     of plants and animals on earth.

ii) They show great variation in shape, size, nutrition, habitat, character etc.

iii)   It could be impossible to remember the identifying characters of each one of them individually du to variations.

iv)   It is also impossible to study various kinds of plants and animals without arranging them into definite groups.

v) If the organisms are collected, scientifically studied and systematically studied arranged into groups, then thy can be easily studied.

vi) Therefore, such a systematic arrangement of organisms based upon similarities and dissimilarities i.e. Classification is necessary.

    Significance of classification:

i) It brings in the diversity of organisms.

ii) It helps in the scientific study of organism

iii)   It helps to understand similarities and differences between organisms.

iv)   It helps to study and understand the large quantity and vast variety of organisms.

v) It helps to determine the exact position of organism in classification system.

vi) It gives the information about the origin evolution of organism.

vii)  It also helps to know evolutionary relationship between different groups of organisms.

viii) It helps in research work.

ix)   It helps to discover new species of plants and animals.

    The system of giving scientific names to each properly identified plants or animals is called nomenclature.

   BINOMIAL NOMENCLATURE

    The method of giving scientific names to an individual which consist of two words, generic and specific is called binomial nomenclature.

    Explanation:

i) This system of nomenclature was developed by Carolus Linnaeus (1753)

ii) Linnaeus gave certain principles for this nomenclature in his book species Plantarum.

iii)   The binomial nomenclature follows certain rules laid by International code of Botanical Nomenclature (ICBN):

i) The scientific name consists of two words or two names or two parts.

ii) First name is of genus i.e. generic.

iii)   Second name is of species i.e. specific name.

iv)   The generic name is written first like a noun and it always starts with capital letter.

v) The specific name is usually an adjective and it starts with small letter.

vi)   The scientific names are given in Latin or Greek language.

vii) The scientific name should be printed in italics and underlined when in hand written form.

viii) The name of scientist (who first identified and named the plant) should be written after the specific name in Roman and without comma between them

ix)   To avoid confusion no two plants / animals can have the same name.

x)    The generic name is short. The specific name should be short but can be compound, e.g. Hibiscus rosasinensis.

    Example:

i) Homo               sapiens Linn.

ii) Mangifera       indica    Linn

    Generic name Specific name     name of the scientist

   Significance of binomial nomenclature:

1) Binomial names are simple and meaningful.

2)   They are precise, definite and self-descriptive.

3)   They are based on some characteristic of the organism.

4)   The names are in Greek or Latin so accepted all over the world (Latin is dead language and not used in any country)

5)   They indicate relationships between organisms.

6)   They avoid confusion created by common names in different areas.

7)   Scientific name is universally common in different countries.

8)   Organisms are known by the same name throughout the world.

    Taxon

    The group of organisms belonging to a definite category in classification system is called is taxon. (H.J. Lam 1984).

    Taxonomic Categories (Units of classification)   

    The taxonomic categories are also called as units of classification.

    The various obligate categories used in classification are -

   1.    Species:

i) The group of organisms which are similar in their vegetative and reproductive characters i.e. Morphological and interbreed truly is called species.

ii) It is basic unit of classification.

iii)   They are derived from common ancestor.

e.g. i)     Mangifera indica (Mango) - here indica is the name of species.

ii) Hibiscus rosa - sinensis (china rose) - Here rosa - sinensis is t name of species which include all the individuals of china rose plant.

iv)   They show similarity in their vegetative and reproductive characters.

v) The individuals of same species interbred freely in nature and produce fertile offspring.

   2. Genus:

i) The group of closely related species which are having the similar reproductive characters is called genus.

ii) They differ in vegetative characters.

iii)   All the species of genus have common features called corelated characters.

iv)   All the species of genus are derived from common ancestor.

e.g. i)     Solanum tuberosum (Potato), Solanum melongena (Brinjal), tuberosum and melongena are two species of some genus Solanum.

   3. Family:

i) The group of related genera which have certain common character is called family

ii) It is higher category than genus.

iii)   The genera of a family have one or another corelated characters which indicate common ancestry.

iv)   The name of family ends with ‘aceae’ or ‘eae’.

e.g. The genera Brassica, Raphanus have some common characters (cruciform corolla) and hence place in family Cruciferae (Brassicaceae)

   4. Order: (Cohort)

i) The group of one or more related families with some common characters is called order.

ii) It is category of higher than family

iii)   The families of one order shows similarity in few characters.

iv)   The name of order ends with ‘ales.

e.g.        Families like Cruciferae, papaveraceae, capparidaceae are placed under the order Parietals (parietal placentation).

   5. Class:

i) The group of closely related orders is called class.

ii) The name of class ends with ‘a’ or ‘opsida’.

iii)   Class Dicotyledonae includes several orders like parietals, malvales, Rosales etc with two cotyledons, taproot system, reticulate venation.

iv)   When class is larger, it is sub-divided into sub-classes and sub classes into series.

e.g.        Dicotyledonae, Monocotyledonae.

   6. Division or phylum.

i) The group of classes having similar characters is called division.

ii) The name of division ends with ‘phyta’.

iii)   The term phylum is used for animals and divisions as Angiosperms and gymnosperms.

   7. Kingdom:

i) The group of divisions or phyla having organisms with few basic common characters is called kingdom.

ii) It is the highest category in the classification.

iii)   It is group of divisions or phyla which have few basic common characters.

iv)   In two kingdom system (Linnaeus), all the plants are included in kingdom - plantae and all animals are included in Kingdom - Animalia

v) But now five kingdom of living organisms are known -

e.g. Monera, Protista, Plantae, Fungi and Animalia.

    The sequence of arrangement of different taxonomic categories in a descending order on the basic of their ranks is called taxonomic or systematic hierarchy.

    Five kingdom classification of Whittaker is based on the following criteria -

i) Complexity of cell structure

ii) Complexity of body organization

iii)   Mode of relationship

   1.    Complexity of cell structure

i) The organisms are primarily divided on three basis of cell structure into prokaryotes and eukaryotes.

ii) Prokaryotes are those organisms in which the cell are without well organised nucleus or membrane bounded structure.

iii)   Eukaryotes are those organisms with cell organised nucleus in their cells (with membrane bounded structures)

    e.g. protists, plantae, fungi, animalia etc.

   2. Complexity of organism’s body:

i) The organisms may be unicellular or multicellular acc/to their organization

ii) In unicellular organisms, the single cell performs all the activities i.e. no division of labour.

iii)   In multicellular organisms many cells are present which grouped into tissue into organs, organs into organ system etc, and performs specific functions i.e. division of labour is present.

   3. Mode of Nutrition:

    Two main modes of nutrition are found in organisms:

i) Autotrophic Nutrition: (Auto - self - tropic - producing)

    The organisms synthesize their own food from simple inorganic substance like water, Co2, minerals, H2s etc. It is further of two types -

a) Photosynthetic autotrophs: The autotrophic organisms which use light as a source of energy and synthesize organic food are called photosynthetic autotrophs.

    e.g. Cyanobacteria, algae, bryophytes, higher plants.

b)    Chemosynthetic autotrophs: The autotrophic organisms which synthesize organic compounds with the help of energy released during chemical reaction are called chemosynthetic autotrophs.

    e.g. Many bacteria - iron bacteria, Sulphur bacteria, etc.

ii) Heterotrophic Nutrition: (Hetero-others)

    The organisms are unable to synthesize their own food, and are dependent on other organisms or organic matter.

   It is further of two types:

   a) Holozoic (ingestive):

    When the organisms ingest or intake food in solid from, the mode of nutrition is called holozoic nutrition e.g. Protozoans, and higher animals

   b) Holophytic (absorptive):

    When the organisms absorb food in liquid form, the mode of nutrition is called Holophytic nutrition.

i) Parasitic nutrition: If the source is another organism

    e.g. Some bacteria, fungi, non-green angiosperms, leech, etc.

ii) saprobic nutrition: When the source of food is dead, decaying organic matter.

    e.g. Most fungi, bacteria, etc.

    General Characters of Kingdom Monera:

i) They are microscopic prokaryotic unicellular or multicellular.

ii) They are motile and nonmotile.

iii)   They are adopted to all types of habitats (living places). i.e. ubiquitous.

    e.g. Hot springs, ocean bottom, snow, dust, in an outside of organism’s body, sulphur spring etc.

iv)   All have single envelope organization (i.e. whole protoplast is covered by plasma membrane but internal compartmentalisation is absent).

v) Rigid cell wall is present, made up of peptidoglycans or Murein.

vi)   The genetic material is the circular, double stranded, helical DNA.

vii) They lack nuclear membrane (i.e. organised nucleus is absent)

viii) DNA lies as a coiled mass in the cytoplasm called as nucleoid

ix)   Membrane bounded cell organelles i.e. mitochondria, Golgi complex, plastids, endoplasmic, reticulum etc. are absent

x)    Nutrition may be autotrophic or heterotrophic. They may be photosynthetic, chemosynthetic, saprotrophic, parasitic or symbiotic.

xi)    Reproduction is primarily asexual by budding or binary fission.

xii)   Many monerans fix atmospheric nitrogen and enrich the soil.

xiii) Flagella, if present, consist of intertwined chains of flagellin protein.

xiv) Respiration may be aerobic or anaerobic.

     General Characters of Kingdom Protista

i)   They are unicellular, eukaryotic organisms, some forms colonics.

ii) They are mostly aquatic organisms.

iii)    Cell wall may not present, if present contains cellulose.

iv)    The organization is of two envelope type i.e. with outer cell membrane around cytoplasm and number of membranes bound organelle’s inside cytoplasm

v) A well-defined nucleus is present, they can b uninucleate, binucleate or multinucleate.

vi)    The genetic material is linear, double stranded helical DNA associated with histone proteins and forms chromosomes.

vii)   Membrane bounded organelles such as mitochondria, plastids, endoplasmic reticulum, Golgi complex Ribosomes, (80S) are present.

viii) Locomotory organs as flagella, cilia, pseudopodia may present, some are non-motile.

     (Flagella, cilia show 9 + 2 pattern of microtubules).

ix)    Nutrition may b -photosynthetic, holozoic, saprophytic or parasitic.

x) Reserved food is starch, glycogen, fat, etc.

xi)    Reproduction occurs by both asexual and sexual methods.

xii)   Asexual reproduction by budding binary fission etc.

xiii) Sexual reproduction by no jacketed gametangia.

     General character of kingdom Plantae:

i)   They are mostly multicellular, eukaryotic organisms except few which are unicellular.

ii) Cells have rigid cell wall made up of cellulose.

iii)    Cells are organised into tissues, organs, organ systems.

iv)    Growth is indefinite with meristematic tissues.

v) Locomotion is absent except in some lower forms.

vi)    Mostly autotrophic (Photosynthetic) and some are heterotrophic - may be total or partial parasites.

vii)   Some autotrophic plants are insectivorous, g. Drossera, Nepenthes, etc.

viii) Photosynthetic plastids are called chloroplasts having photosynthetic pigments as chlorophyll a, b, xanthophyll, carotenes, etc.

ix)    Reserve food is starch and fat.

x) Reproduction occurs by both sexual and asexual method.

xi)    These are main food producers on land and in water.

   General character of Kingdom Fungi:

i)   Mostly multicellular, eukaryotic organisms, only yeasts are unicellular.

ii) There is total absence of chlorophyll or other photosynthetic pigments.

iii)    The plant is extremely delicate, thread like and branched called mycelium.

iv)    The filaments (threads) of mycelium are called hypha

v) The hyphae may be multinucleate and non-septate (coenocytic) in lower forms of divided by septa (cross - walls) into uninucleate cells.

vi)    Cell wall contains fungal cellulose or chitin or both (but never pure cellulose).

vii)   Reserve food is glycogen, fat and oil.

viii) They are heterotrophic with absorptive mode of nutrition.

ix)    Accordingly, fungi may be saprophytic (penicillium, mushrooms), parasitic (algugo, phytophthora), symbiotic (Lichens, mycorrhiza) etc.

x) Reproduction by vegetative, asexual and sexual methods.

     General Characters of Kingdom animalia:

i)   They are multicellular, eukaryotic organisms.

ii) The photosynthetic pigments and chloroplast are absent.

     Cells are without cell wall.

iii)    They have nerve cells; sense organs & nervous system hence show co - ordinate movements and quick response to stimuli.

iv)    They are heterotrophic and obtain their food directly or indirectly from plants.

v) Nutrition is holozoic or ingestive type.

vi)    Few are parasitic on or inside the body of other organisms.

vii)   They are motile and show locomotion.

viii) Reproduction is mostly sexual and embryo stage present.

ix)    May be aquatic, terrestrial, amphibious or parasitic in habitat.ae forms are diploid stages.

x)     The animal kingdom shows greater diversity than others.