The Living World_Notes

Characteristics exhibited by living organisms

1. Growth
2. Reproduction
3. Metabolism
4. Ability to sense environment (Consciousness)
5. Cellular organisation

GROWTH

• Increase in mass and increase in number of individuals are twin characteristics of growth.
• A multicellular organism grows by cell division.
• In plants, this growth by cell division occurs continuously throughout their life span.
• In animals, this growth is seen only up to a certain age.
• In majority of higher animals and plants, growth and reproduction are mutually exclusive events.
• Non-living objects also grow if we take increase in body mass as a criterion for growth. Mountains, boulders and sand mounds do grow

REPRODUCTION

• In multicellular organisms, reproduction refers to the production of progeny possessing features more or less similar to those of parents.

• Fungi multiply and spread due to the millions of asexual spores they produce.
• In lower organisms like yeast and hydra reproduce by budding.
• In Planaria (flatworms) a fragmented organism regenerates the lost part of its body and becomes a new organism.-TRUE REGENERATION
• The fungi, the filamentous algae, the protonema of mosses etc multiply by fragmentation.
• reproduction also cannot be an all-inclusive defining characteristic of living organisms.

METABOLISM

• All living organisms are made of chemicals. These chemicals, small and big, belonging to various classes, sizes, functions, etc., are constantly being made and changed into some other biomolecules.
• These conversions are chemical reactions or metabolic reactions.
• The sum total of all the chemical reactions occurring in our body is metabolism.
• Metabolic reactions can be demonstrated outside the body in cell-free systems.
• Isolated metabolic reactions in vitro are not living things but surely living reactions.

CONSCIOUSNESS

• Living organisms are self-replicating, evolving and self-regulating interactive systems capable of responding to external stimuli.
• All living organisms are linked to one another by the sharing of the common genetic material, but to varying degrees.

CELLULAR ORGANISATION

• living organisms consist of cells & their products.

DIVERSITY IN THE LIVING WORLD:

Biodiversity:  The number of species comes to the range between 1.7 – 1.8 million

Nomenclature: There are millions of plants and animals in the world; their names need to be standardised all over the world. This process is called nomenclature.

Identification:
Nomenclature or naming is only possible when the organism is described correctly and the name is attached to. This is identification.
For plants, scientific names are based on agreed principles and criteria, which are provided in International Code for Botanical Nomenclature (ICBN).

• For animals International Code of Zoological Nomenclature (ICZN).

Binomial Nomenclature:

• This naming system given by Carolus Linnaeus is being practised by biologists all over the world.

• Universally accepted principles to provide scientific names to known organisms.
• Each name has two components – the Generic name and the specific epithet.

Eg. Panther leo – Panther –generic name, leo-specific epithet

Universal rules of nomenclature are as follows:

1. Biological names are generally in Latin and written in italics. They are Latinised or derived from Latin irrespective of their origin.
2. The first word in a biological name represents the genus while the second component denotes the specific epithet.
3. Both the words in a biological name, when handwritten, are separately underlined, or printed in italics to indicate their Latin origin.
4. The first word denoting the genus starts with a capital letter while the specific epithet starts with a small letter.

Example – Canis familaris.

5. Name of the author appears after the specific epithet, i.e., at the end of the biological name and is written in an abbreviated form, e.g., Mangifera indica Linn.

Classification

It is the process by which anything is grouped into categories based on some easily observable characters. Hence, based on characteristics, all living organisms can be classified into different taxa. This process of classification is taxonomy.

Characterisation, identification, classification and nomenclature are the processes that are basic to taxonomy.

• Based on characteristics, all living organisms can be classified into different taxa. This process of classification is taxonomy.
• External and internal structure, along with the structure of cell, development process and ecological information of organisms are essential and form the basis of modern taxonomic studies.

 Systematics

• The word systematics is derived from the Latin word ‘systema’ which means systematic arrangement of organisms.
• 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.

TAXONOMIC CATEGORIES

• Classification is not a single step process but involves hierarchy of steps in which each step represents a rank or category.
• 7 OBLIGATE CATEGORIES/RANK
• Each category, referred to as a unit of classification, in fact, represents a rank and is commonly termed as taxon (pl.: taxa).
• Real organism belong to taxon

• 7 OBLIGATE CATEGORIES/RANK

1. Kingdom
2. Phylum/Division
3. Class
4. Order
5. Family
6. Genus
7. Species

(I)  Species

• Study of a group of individual organisms with fundamental similarities as a species.
• Based on morphological differences.
• Example – Mangifera indica, Solanum tuberosum (potato) and Panthera leo (lion). All the three names, indica, tuberosum and leo, represent the specific epithets

(II) Genus

• Group of related species which has more characters in common in comparison to species of other genera.
• potato and brinjal are two different species but both belong to the genus Solanum. Lion (Panthera leo), leopard (P. pardus) and tiger (P. tigris) with several common features, are all species of the genus Panthera.

(III) Family

• A group of related genera with still less number of similarities as compared to genus and species.
• Families are characterised on the basis of both vegetative and reproductive features of plant species.
• Examples-Solanum, Petunia and Datura are placed in the family Solanaceae.
• Genus Panthera, comprising lion, tiger, leopard is put along with genus, Felis (cats) in the family Felidae.
• Cat family-Felidae and dog family-Canidae

(IV) Order

• Order and other higher taxonomic categories are identified based on the aggregates of characters.
• 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.
• Plant families like Convolvulaceae, Solanaceae are included in the order Polymoniales mainly based on the floral characters.
• The animal order, Carnivora, includes families like Felidae and Canidae.

(V) Class

• Includes related orders.
• For example, order Primata comprising monkey, gorilla and gibbon is placed in class Mammalia along with order Carnivora that includes animals like tiger, cat and dog.
• Class Mammalia has other orders also.

(VI)  Phyllum/Division

• Classes comprising animals like fishes, amphibians, reptiles, birds along with mammals based on the common features like presence of notochord and dorsal hollow neural system, are included in phylum Chordata.
• Phylum of kingdom animalia-

1.porifera

2.cnideria

3.ctenophora

4.platyhelminthes

5.aschehelmithes

6.annelida

7.arthropoda

8.mollusca

9.echinodermata

10.hemichordata

11.chordata

• In case of plants, classes with a few similar characters are assigned to a higher category called Division.
• Division of kingdom plantae

1.algae

2.bryophyte

3.pteridophyte

4.gymnosperm

5.angiosperm

VII. Kingdom

• All animals belonging to various phyla are assigned to the highest category called Kingdom Animalia
• The Kingdom Plantae, on the other hand, is distinct, and comprises all plants from various divisions.

TAXONOMICAL AIDS

1. Herbarium
2. Botanical garden
3. Museum
4. Zoological park
5. key
6. Flora
7. Fauna
8. Manual
9. Catalogue
10. Monograph
11. HERBARIUM

• Herbarium is a store house of collected plant specimens that are dried, pressed and preserved on sheets.
• These sheets are arranged according to a universally accepted system of classification.
• These specimens, along with their descriptions on herbarium sheets, become a store house or repository for future use.
• The herbarium sheets also carry a label providing information about date and place of collection, English, local and botanical names, family, collector’s name, etc.
• Herbaria also serve as quick referral systems in taxonomical studies.

2. BOTANICAL GARDEN

• These specialised gardens have collections of living plants for reference.
• Plant species in these gardens are grown for identification purposes and each plant is labelled indicating its botanical/scientific name and its family.
• The famous botanical gardens are at Kew (England), Indian Botanical Garden, Howrah (India) and at National Botanical Research Institute, Lucknow (India).

3. MUSEUM

• Biological museums are generally set up in educational institutes such as schools and colleges.
• Museums have collections of preserved plant and animal specimens for study and reference.
• Specimens are preserved in the containers or jars in preservative solutions. Plant and animal specimens may also be preserved as dry specimens.
• Insects are preserved in insect boxes after collecting, killing and pinning.
• Larger animals like birds and mammals are usually stuffed and preserved.
• Museums often have collections of skeletons of animals too.

4. ZOOLOGICAL PARKS

• 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.
• All animals in a zoo are provided, as far as possible, the conditions similar to their natural habitats.

5. KEY

• 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.

• This results in acceptance of only one and rejection of the other. Each statement in the key is called a lead.
• Separate taxonomic keys are required for each taxonomic category such as family, genus and species for identification purposes. Keys are generally analytical in nature.

6. FLORA

• Flora contains the actual account of habitat and distribution of plants of a given area

7. FAUNA

• Fauna contains the actual account of habitat and distribution of animals of a given area

8. MANUAL

• useful in providing information for identification of names of species found in an area

9. CATALOGUE

• a complete list or a booklet or register, which comprises a list of characters and their alternates present in various taxa

10. MONOGRAPH

• Monographs contain information on any one taxon.

MONOGRAPH OF PAPAYA TREE