THE LIVING WORLD
THEORETICAL PARTS
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1. CHARACTERISTICS OF LIVING ORGANISM
1.1 Growth
- All living organisms grow.
- Increase in mass and increase in number of individuals are twin characteristics of growth.
- Non-living objects also grow if we take increase in body mass as a criterion for growth.
- However, this kind of growth exhibited by non-living objects is by accumulation of material on the surface.
- In living organisms, growth is from inside.
- Growth, therefore, cannot be taken as a defining property of living organisms.
1.2 Reproduction
- Reproduction, likewise, is a characteristic of living organisms.
- In multicellular organisms, reproduction refers to the production of progeny possessing features more or less similar to those of parents.
- Organisms reproduce by asexual means also.
- There are many organisms which do not reproduce (mules, sterile worker bees, infertile human couples, etc).
- Hence, reproduction also cannot be an all-inclusive defining characteristic of living organisms.
1.3 Metabolism
- The sum total of all the chemical reactions occurring in our body is metabolism.
- No non-living object exhibits metabolism.
- Hence, cellular organisation of the body is the defining feature of life forms.
1.4 Consciousness
- Human being is the only organism who is aware of himself, i.e., has self consciousness.
- Consciousness therefore, becomes the defining property of living organisms.
2. NOMENCLATURE
- Naming of organisms.
- The names are unique and universal.
- Rules for nomenclature are provided by:
- ICBN – International Code for Botanical Nomenclature
- ICZN – International Code for Zoological Nomenclature
- Each name has two components – the Generic name and the specific epithet.
- This system of providing a name with two components is called binomial nomenclature.
- This naming system given by Carolus Linnaeus is being practised by biologists all over the world.
- Carolus Linnaeus – Father of Taxonomy
- Guidelines and Principles for Nomenclature:
- (a) It should be in Latin / derived from Latin.
- (b) If it is written in Italics when types and underlined when handwritten.
- (c) It contains two parts, the first word is Genus ; the second word is Species.
- (d) Genus name starts with Capital while species name starts with small letters.
- (e) Name should be short, precise and easy to pronounce.
- (f) Name of the author is written as an abbreviated form after the species name.
- e.g. Mangifera indica Linn.
- Example: Mangifera indica ( Mango)
- Homo sapiens ( Human)
- Panthera pardus (Leopard)
- Felis domestica (Cat)
- Tautonym- A taxonomic designation, such as Gorilla gorilla, in which the genus and species names are the same, commonly used in zoology but no longer in botany.
3. CLASSIFICATION
- Classification is the process by which anything is grouped into convenient categories based on some easily observable characters.
- The scientific term for these categories is taxa.
- Based on characteristics, all living organisms can be classified into different taxa. This process of classification is taxonomy.
- Systematics is the study of different kinds of organisms and their relationships.
- Linnaeus used Systema Naturae as the title of his publication.
- The scope of systematics was later enlarged to include identification, nomenclature and classification.
- Systematics takes into account evolutionary relationships between organisms.
4. TAXONOMIC CATEGORIES
- Taxonomy is the science of naming, defining and classifying groups of biological organisms on the basis of shared characteristics.
- Taxonomic hierarchy is the process of arranging various groups of organisms, into successive levels of the biological classification in a sequence either in a decreasing or increasing order from kingdom to species and vice versa.
- Each category, referred to as a unit of classification, in fact, represents a rank and is commonly termed as taxon.
- Species: a group of individual organisms with fundamental similarities.
- Genus comprises a group of related species which has more characters in common in comparison to species of other genera.
- Family, has a group of related genera with still less number of similarities as compared to genus and species.
- Order being a higher category, is the assemblage of families which exhibit a few similar characters. The similar characters are less in number as compared to different genera included in a family.
- Class, this category includes related orders.
- Phylum, classes comprising animals like fishes, amphibians, reptiles, birds along with mammals constitute the next higher category called phylum.
- Kingdom- All animals belonging to various phyla are assigned to the highest category called Kingdom Animalia in the classification system of animals. The Kingdom Plantae, on the other hand, is distinct, and comprises all plants from various divisions.
5. TAXONOMICAL AIDS
5.1 Herbarium
- Herbarium is a store house of collected plant specimens that are dried, pressed and preserved on sheets.
5.2 Botanical Gardens
- These specialised gardens have collections of living plants for reference.
- The famous botanical gardens are at Kew (England), Indian Botanical Garden, Howrah (India) and at National Botanical Research Institute, Lucknow (India).
5.3 Museum
- Museums have collections of preserved plant and animal specimens for study and reference.
5.4 Zoological Parks
- These are the places where wild animals are kept in protected environments under human care and which enable us to learn about their food habits and behaviour.
5.5 Key
- Key is another taxonomical aid used for identification of plants and animals based on the similarities and dissimilarities.
- The keys are based on the contrasting characters generally in a pair called couplet.
- It represents the choice made between two opposite options.
- Each statement in the key is called a lead.
- Keys are generally analytical in nature.
- Flora, manuals, monographs and catalogues are some other means of recording descriptions.
- Flora contains the actual account of habitat and distribution of plants of a given area.
- Manuals are useful in providing information for identification of names of species found in an area.
- Monographs contain information on any one taxons.
