Living World II

Herbarium

A herbarium is a collection of plants, which have been dried, pressed and mounted on herbarium sheets, identified and classified according to some approved system of classification. Most countries possess their own plant collections (herbaria). The greatest herbarium of the world is at the Royal Botanic Gardens, Kew, Eng1an9. The biggest herbarium of our country is at the Indian Botanic garden, Calcutta, possessing about one million specimens.

The details of structure and development of a plant cannot be studied by means of drawings and photographs. Most comparative studies for taxonomic purposes are made in the herbarium and laboratories. The newly collected specimens are identified by the comparison of their morphology and the morphology of plants stored in the herbarium.

Various instruments used are:

a.  Field note book: It is the most important instrument of plant collection. It is a small note pad in which the relevant data like, locality, ecological point, habits etc of the plant are noted down.

b.  Small instrument Kit: This consists of needles, a razor blade, a magnifier, and a pair of forceps.

c.  Digging and scraping instruments: These are used when small plants are to be digging out or when some Bryophytes or Lichens are to be scraped out.

d.  Vasculum:  A special metallic box - for keeping plants for several hours before bringing them to laboratory.

e.  Plant Press: There are various kinds. These are used for pressing plants that are to be put on to a herbarium sheet. The most widely used press is one which is made up of wooden plank.

a.    Drying sheets: These are special absorbant paper which are used to dry specimen.

Disinfecting and Mounting

The dried specimens are treated with poisonous solution a precaution against fungal and insect infections. Eg. Mercuric bichloride is the most widely used poison.

Mounting of specimen needs special skill and experience. Specimens are pasted to standard herbarium sheets. The glue is spread over a glass plate, the specimen is then placed over it with face uppermost, it is then removed and kept on to the herbarium sheet. A newspaper sheet is placed over it to remove excess of glue. Such mounted sheets are placed one over the other and a plank is placed over it for proper fixing.

Storage of Herbarium Sheets

The herbarium sheets are better stored in a special room. The sheets are stored in wooden or steel shelves containing pigeon holes of describable size. These are arranged according to a well-known taxonomic system. In India BENTHAM and HOOKER'S system of classification is followed. These are arranged family wise, within family genera wise and the genus species wise. 

Zoological Park

Zoological parks are public institutions where wild animals are exhibited for promoting interest, love and awareness among the people. There are more than 300 zoological parks in India. The main aim of such parks is to increase public interest and understanding of wild life. It also provides recreation and education. Now-a-days zoos are also involved in the conservation of endangered species. Protection of wild life from extinction requires conservation of natural habitats and ecosystems, and captive breeding of species.

A zoo generally keeps mammals, birds, reptiles, amphibians and arthropods. It includes lion, tiger, leopards, elephants, wolves, foxes, camels, giraffes, horses, zebras, asses, rhinoceros, deer, mountain goats, sheep, kangaroo and many more. Aquatic animals are also displayed in artificial ponds or watercourses. Zoos in foreign countries show dolphins and seals in big tanks.

Zoological parks undertake many other activities such as animal rides, animal shows, film shows, adoption of animals, research and training.

Delhi zoo and Chhat Bir zoological park, Punjab are famous zoological parks of India.

Biological Museums.

Biological museums have collection of preserved plant and animal specimens for study and reference. Specimens are preserved in containers or jars in preservative solution, insect boxes or as dry specimens. Objects exhibited in museums include stuffed animals, stuffed heads, preserved animals, skeleton, bird's beak, eggs of rare species or extinct birds, shells, tusks, fossils etc.

 

THE LIVING WORLD

Learning Points

v  Living and its characters

v  Diversity in living world

v  Biodiversity

v  Nomenclature

v  Binomial nomenclature

v  Generic and specific names

v  .Identification

v  Classification

v  Taxonomy and systematics

v  Taxonomic categories

v  Hierarchy

The living world shows great diversity both in form and habitat. The range of size and form among the living beings is amazing. Some members live in extra ordinary habitats like deep sea, hot springs, hot deserts, cold mountains and so on. The beauty and charm, the living world imparts is beyond description.

The conflict and co-operation among the populations and the organization as well as interactions of molecules with in· the organisms are another wonder. It poses a fundamental question-what indeed is life or how it differs from the non living in a scientific point of view? Try to answer the question what is living on the ground of these.

1. What is living

We can present many distinctive characters exhibited by living organisms such as growth, reproduction, response to stimuli or features like metabolism, ability to self replicate, self organize etc. Let us try to understand these characters.

1.1 Growth

Growth is irreversible increase in mass and size of cells, tissues, organs or an organism. The plants and animals grow by cell division. In. plants, cell division occurs only in some regions but occurs continuously through out their life span. In animals, growth by division ceases at a certain age, however cell division for the replacement of lost cell continues. In un i-cellular organisms, increase in number of cells by cell division, can be considered as a measure of growth. But in higher organisms, growth and reproduction are two mutually exclusive events.

If we take increase in mass as the criterion of growth, the increase in mass of mountains, sand mounds or a crystal could also be considered as growth. However this kind of growth by the accumulation of materials differs from that of living beings. The growth of living organism is from inside the body. Thus we can conclude that growth is a characteristic of living systems but not a defining property of living organisms. Growth is the net result of two opposing components of metabolism, namely anabolism or build-up processes and catabolism or break-down processes. Growth is zero if the two are equal. It is negative or degrowth if catabolism is more than anabolism.

1.2 Reproduction

Living organisms can reproduce by different methods. Fungi and algae can reproduce by sexual spores. Yeast and Hydra reproduce by budding. Planaria is capable of regeneration. Algae, fungi and bryophytes can reproduce by fragmentation. In all the above methods the progenies resemble their parent in all respects. In sexual reproduction the off springs show some variations from the parents. But there are organisms which cannot reproduce, for example a mule or worker bee. Some human couples are also infertile. Hence all living organisms are not capable of reproduction, of course non living objects are not in a state of reproduction. All these can be summarised as the reproduction in living organisms are of vegetative, asexual, and sexual methods.

1.3 Metabolism

All living organisms are made up of chemicals of various classes, and functions. These are continuously being converted into other molecules. These convertions of molecules in a sequence of reactions are called metabolic reactions. In all plants, animals and microbes thousands of metabolic reactions take place simultaneously. The sum total of all the chemical reactions taking place in the body of an organism is called metabolism. Metabolisms do not occur in non living objects. However metabolic reactions can be performed in a cell free system. Such a reaction in vitro is not a living character, but definitely a living reaction. Thus metabolism is a defining feature of living organism. A cellular organization is required for metabolism. Hence cellular organization of body is also a defining feature of living organisms. Again, the facts like metabolism and cellular organization are the other features of living organisms.

1.4 Consciousness

The living organisms are capable of sensing physical, chemical or biological changes occuring in their surroundings. They also respond to such environmental changes. Animals have better sense organs and their responses are quick. Plants and microbes also respond to various external factors like temperature, chemicals etc. They can also respond to the presence of other organism. Photoperiod influences the reproduction in both plant and animals. Thus all organisms are 'aware' of their environment, further human beings are aware of him/her self or have self consciousness. Hence consciousness can be considered as a defining property of life.

To conclude, 'life' is a property exhibited by the underlying interaction. It must be noted that properties of organelles are not present in the molecular components but is a result of the interactions of the molecules. Similarly the property of tissue is the result of assemblage and co-ordination of constituent cells, and not the properties of cell. Thus interactions at one level generate the properties at a higher level of organization. This is true in the hierarchy of organisational complexity at all levels. Therefore living organisms are, self replicating, evolving, self regulating and interactive system capable of responding to external stimuli. All living organisms of the past, present and future share the common genetic material but to a varying degree of diversities. Biology is the story of life and its evolution.

2. Diversity in the living world

The common plants and animals of our own area may have local names. These names vary from place to place and are not useful for communication among the scientists in different parts of the world. Further all plant or animal may not have a name. Hence there must be a system of naming such that a particular organism is known by the same name all over the world. The organism must be properly identified and described before naming. It should also ensure that one organism has only one correct name. The process of naming is called nomenclature.

Scientists have Established procedure, for nomenclature acceptable to biologists all over the world. The principles and criteria for assigning, scientific name to plants are provided in the International Code for Botanical Nomenclature (ICBN). For the naming of animals, taxonomists have evolved International Code for Zoological Nomenclature (lCZN).  The scientific name therefore ensures proper identification of an organism by the same name all over the world.

The universally accepted name is called scientific name. Each scientific name has two epithets or names. The first part is called the generic name and the second part, the specific epithet. Such a system of naming an organism with two names is called Binomial nomenclature. This system was introduced by Carolus Linnaeus and is universally accepted. 

This system can be illustrated with the help of the scientific name of mango tree. The scientific name of mango tree is Mangifera indica_Linn. The Mangifera is the generic name while indica represents the specific epithet. The name of the scientist who first described the organism (author) is also written in abbreviated form at the end of the biological name. In the above example Linn stand for Linnaeus who first described and named the plant.

A proper study or under standing of diverse living world is possible only if we group the organisms based on some of their identifiable characters. For example when we think of dog we identify some characters common to all dogs by which we can distinguish dogs from cats or the plant wheat from rice. Similarly we can recognize boarder categories like mammals birds, fishes, ferns or even plants and animals. Such convenient categories used in the study of organisms are technically called taxa (Singular taxon) you must note that the taxa indicate categories at different level. For example cats and dogs are mammals, Mammals and birds are animals.

The process of classifying organisms into different taxa based on their characteristics is called taxonomy. Taxonomic studies consider external and internal structure along with the structure of cell, developmental process and ecological information of the organisms. Therefore the basic processes in taxonomy are characterization, identification, classification and nomenclature. 

A Brief History of Classification

ü   Hippocrates and Aristotle arranged animals into insects, birds, fishes and quadripeds and whales.

ü   Theophrastus grouped plants under trees, shrubs, undershurbs and herbs. He described 480 plants in his book 'Historia Plantarum'. Theophrastus is known as the Father of Botany.

ü   John Ray described about 18,600 plants in three volumes of Historia Generalis Plantarum. JOHN RAY also coined the term species.

ü   Carolus Linnaeus described 5900 species of plants in his book Species Plantarum and 4326 species of animals in Systema Naturae. His system of classification was regarded as artificial and sexual system. LINNAEUS is considered as the Father of Taxonomy.

ü   Later on systematists like BENTHAM and HOOKER took into account many characters. It brought out natural affinities in plants and later proposed the natural system of classification.

ü    In 1950's a modification of natural system known as numerical taxonomy, taximetrics or phenetics came into existence.

ü   Biologists like ENGLER and PRANTL, HUTCHINSON, CRONQUIST, TAKHTAJAN etc laid their classification systems based on the evolutionary and genetic relationships. This resulted in development of phylogenetic classification or cladistics.

ü   Cladistics led to the formation of a branch called as New Sytematics. The term was coined by JULlAN HUXLEY. It takes into consideration of all types of characters including morphology, cytology, physiology, biochemistry, ecology, genetics, behaviour etc.

ü  Cladistics is actually a synthesis of Several  branches like classical systematics (based on morphological characters), Cytotaxonomy (based on cytological investigations like structure and behaviour of chromosomes), Chemotaxonomy (based on chemical characters like amino acids, proteins, alkaloids, crystals, volatile oils) etc.

The beginning of taxonomy can be traced back to the early days when human beings started classifying various organisms based on their needs such as sources of food, clothing shelter etc. When human beings studied more and more about organisms, they were also aware of the inter relationships among them.

Systematics is the branch of biology which categorise the plants, animals and other organisms. According to G.SIMPSON, Systematics is the science that deals with diversity of organisms and all their comparative and evolutionary relationships based on study of comparative anatomy, biochemistry, physiology and ecology. 

3. Taxonomic Categories

Classification is a step by step process. A taxonomist places an organism into categories. Sequence of categories from lower to higher rank in an ascending order is known as taxonomic hierarchy or Linnaean hierarchy. The hierarchical categories from the lowest to the highest are of seven types. These are speciesà genusà familyà orderà class à division or phylumà kingdom. Each such category is known as taxon.

Species (John Ray)

It is a group of fundamentally similar and potentially interbreeding populations that are reproductively isolated from other such groups due to the morphological features. It is the lowest taxonomic category in classification. Examples: Solanum nigrum, Panthera Ieo and Homo sapiens. Here nigrum, leo and sapiens are the species epithets.

Genus (John Ray)

It is the group or assembly of related species which resemble one another in certain correlated characters. The genera which have only one species are called monotypic whereas those which have many species under a single genus are called polytypic. The genus Solanum has many species like S.tuberosum, S.melongena, S.nigrum etc Panthera leo, (Lion) P. tigris (tiger) P. Pardus (Leopard)are put under the genus Panthera.  Homo sapiens is monotypic (Only one species).

Family (John Ray)

It consists of one or more related genera. Eg: The genera like Solanum, Withania, Datura, Petunia, Nicotiana etc come under the family Solanaceae. Genus Panthera and Felis put under the family Felidae.

Order (Linnaeus)

This category includes one or more related families. Thus the family Solanaceae is placed in the order Polymoniales along with Convolvuiaceae, Boraginaceae, Hydrophyllaceae and Polymoniaceae. The order carnivora includes the family Felidae (cat family) and Canidae (dog family).

Class (Linnaeus)

It is an assemblage of related orders. For example, the class Dicotyledoneae contains the orders Rosales, Polymoniales, Passiflorales, Sapindales, Ranales etc. Carnivora, Primata, Rodentia, Chaetoptera and other orders are included in class Mammalia

Division (Eichler) or Phylum (Cuvier)

It is a category above the class. The term phylum is used for animals while division is commonly employed for plants. This category is formed of one or more classes. Eg: The division Spermatophyta contains the classes, monocotyledons and dicotyledons. All animals with dorsal neural system and notochord like fishes, amphibia, aves, mammalia are put under the phylum Chordata. 

Kingdom

It is the highest taxonomic category. All plants are included in the kingdom Plantae while all animals belong to kingdom Animalia.

Classification of human beings

Species: sapiens   Genus: Homo      Family: Hominidae      Order: Primata   

Class: Mammalia    Phylum:    Chordata      Kingdom:  Animilia.

4. Taxonomical Aids

Taxonomic knowledge is Useful in different fields of science like agriculture, forestry, industry etc. These studies require correct classification and identification of organisms. A collection of actual specimens of plant and animals is the primary requirements for the taxonomical studies. Hence scientists established some techniques and procedures for preserving or storing information and specimens. Some of these are discussed below under the heading like Botanical gardens, Herbarium, Zoological parks, Biological Museums and Taxonomic Keys.

4.1 Botanical gardens

Botanical garden is a place for growing, plants for flowers, fruits or vegetables and also is an educational institution for scientific workers and general public or layman to cultivate an interest in plant life. A botanic garden has:

i.             Collection of different varieties of cultivated plants and ornamental plants.

ii.           Medicinal plants.

iii.          Plants of certain geographic distribution.

iv.          Weeds of various kinds.

v.           Plants of classical nature.

The botanic gardens play a vital role in the economic and aesthetic needs of various nature. In the field of fundamental research, it may be related that the laws of genetics were worked out by Mendel in a monastic garden in Austria.

Some of the important botanical gardens:

ROYAL BOTANIC GARDEN, KEW, ENGLAND:

The Royal Botanic Gardens, Kew, usually referred to simply as Kew Gardens, are 121 hectares of gardens and botanical glasshouses between Richmond and Kew in southwest London, England. It was started as a private garden of SIR HENRY CAPEL. Later it become botanical capital of the world. At present it is under the ministry of agriculture, fisheries and food. The Kew herbarium is one of the largest in the world with approximately 7 million specimens used primarily for taxonomic study. The herbarium is rich in types for all regions of the world.

Indian Botanic Garden, Howrah

Established in 1787 by Lieutenant Colonel Robert Kyd, this garden is situated on the west bank of the river Hooghly (Ganga). The garden covers an area of 273 acres. Its unique landscape design initiated by Sir George King in 1872 is considered to be one of the best in the botanic gardens of the world with undulated land surfaces, artificial lakes and moats interconnected with underground pipes receiving water from the river Hooghly. 

The Great Banyan Tree (Ficus bengalensis L.) of the Indian Botanic Garden attracts millions of visitors every year. It looks like a miniature forest and is over 250 years old with 2800 prop roots covering an area of 1.5 hectares.

The garden was known as East India Company’s Garden or the ‘Company Bagan’ or Calcutta Garden and later as the Royal Botanic Garden which after independence was renamed as the ‘INDIAN BOTANIC GARDEN’ in 1950.It came under the management of the Botanical Survey of India on January 1, 1963.