Category: Biology

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Non Chrodates

Phylum: Porifera (L. poros-pore; ferre-to bear)

These pore bearing animals are commonly called sponges. They are aquatic, mostly marine, asymmetrical and a few species live in freshwaters. They are primitive, multicellular, sessile animals with cellular level of organisation in which the cells are loosely arranged. They are either radially symmetrical or asymmetrical animals.

They possess a water transport system or canal system where water enters through minute pores called ostia lining the body wall through which the water enters into a central cavity (spongocoel) and goes out through the osculum. This water transport system is helpful in food gathering, circulation, respiration and removal of waste. Choanocytes or collar cells are special flagellated cells lining the spongocoel and the canals.

The body is supported by a skeleton made up of calcareous and siliceous spicules or spongin or both. Nutrition is holozoic and intracellular. All sponges are hermaphrodites (i.e.) the ova and sperms are produced by the same individual.

They also reproduce asexually by fragmentation or gemmule formation and sexually by the formation of gametes. Development is indirect with different types of larval stages such as parenchymula and amphiblastula. Examples: Sycon (Scypha), Spongilla (fresh water sponge), Euspongia (bath sponge) Euplectella (Venus flower basket) (Figure 2.9).

Phylum: Cnidaria (G. knode -needle or sting cells)

Cnidarians (were previously called Coelenterata), are aquatic, sessile or free swimming, solitary or colonial forms with radial symmetry. The name Cnidaria is derived from cnidocytes or cnidoblasts with stinging cells or nematocyst on tentacles. Cnidoblasts are used for anchorage, defense, and to capture the prey. Cnidarians are the first group of animals to exhibit tissue level organisation and are diploblastic.

They have a central vascular cavity or coelenteron (serves both digestion and circulatory function) with a single opening called mouth or hypostome, which serves the process of ingestion and egestion. Digestion is both extracellular and intracellular. The nervous system is primitive and is formed of diffused nerve net. Cnidarians like corals have a skeleton made up of calcium carbonate.

Cnidarians exhibit two basic body forms, polyp and medusa. The polyp forms are sessile and cylindrical (e.g. Hydra, Adamsia), whereas the medusa are umbrella shaped and free swimming. Cnidarians which exist in both forms, also exhibit alternation of generations in their life cycle (Metagenesis).

The polyp represents the asexual generation and medusa represents the sexual generation. Polyps produce medusa asexually and medusa forms polyps sexually. Development is indirect and includes a free swimming ciliated planula larva. Examples: Physalia (Portugese man of war), Adamsia (Sea anemone), Pennatula (Sea pen), Meandrina (Brain coral) (Figure 2.10).

Phylum: Ctenophora (G. Ktenos – comb; phoros – bearing)

Ctenophora are exclusively marine, biradially symmetrical, diploblastic animals with tissue level of organisation. Though they are diploblastic, their mesoglea is different from that of cnidaria. It contains amoebocytes and smooth muscle cells. They have eight external rows of ciliated comb plates (comb jellies) which help in locomotion, hence commonly called comb jellies or sea walnuts.

Bioluminescence (the ability of a living organism to emit light) is well marked in ctenophores. They lack nematocysts but possess special cells called lasso cells or colloblasts which help in food capture. Digestion is both extracellular and intracellular. Sexes are not separate (monoecious). They reproduce only by sexual means. Fertilization is external and development is indirect and includes a larval stage called cydippid larva. e.g., Pleurobrachia (Figure 2.11).

Phylum: Platyhelminthes (Flatworms)

(G. Platy -broad or flat; helmin-worm)

They have a dorsoventrally flattened body and hence called flatworms. These animals are bilaterally symmetrical, triploblastic, acoelomate with organ system level of organisation. They show moderate cephalization and unidirectional movement. They are, mostly endoparasites of animals including human beings. Hooks and suckers are present in the parasitic forms and serve as organs of attachment.

Their body is not segmented, but some exhibit pseudosegmentation. Some of the parasitic flatworms absorb nutrients directly from the host through their body surface. However, flatworms like liver fluke have an incomplete digestive system. Specialized excretory cells called flame cells help in osmoregulation and excretion.

Sexes are not separate (monoecious); fertilisation is internal and development is through larval stages (miracidium, sporocyst, redia, cercaria). Polyembryony is common in some flatworms (Liver flukes). Some members like Planaria show high regeneration capacity (Figure 2.12). Examples: Taenia solium (Tape worm), Fasciola hepatica (Liver fluke), Schistosoma (Blood fluke).

Phylum: Aschelminthes (Round Worms)

(G. Askes – cavity; helminths – worms)

Previously called Nematoda, this phylum is now named as Aschelminthes. The body of these worms is circular (round) in cross section and hence are called round worms. They are free living or parasitic on aquatic and terrestrial plants and animals. They are bilaterally symmetrical, triploblastic and pseudocoelomate animals with organ system level of organisation.

The body is unsegmented and covered by a transparent, tough and protective collagenous layer called cuticle. The alimentary canal is complete with a well developed mouth, muscular pharynx and anus. Excretory system consists of renette glands. Sexes are separate; and exhibit sexual dimorphism; often females are longer than males. Fertilisation is internal; majority are oviparous (e.g. Ascaris) few are ovoviviparous (Wuchereria). Development may be direct or indirect.

Examples. Ascaris lumbricoides (Round worm), Enterobius vermicularis (Pin worm), Wuchereria bancroft (Filarial worm), Ancylostomaa deuodenale (Hook worm) (Figure 2.13).

Phylum: Annelida (Segmented worm)

(L. annulus – a ring, and G. edios – form)

Annelids were the first segmented animals to evolve. They are aquatic or terrestrial, free living but some are parasitic. They are triploblastic, bilaterally symmetrical, schizocoelomates and exhibit organ system level of body organisation. The coelom with coelomic fluid creates a hydrostatic skeleton and aids in locomotion. Their elongated body is metamerically segmented and the body surface is divided into segment or metameres.

Internally the segments are divided from one another by partitions called septa. This phenomenon is known as metamerism. The longitudinal and circular muscles in the body wall help in locomotion. Aquatic annelids like Nereis have lateral appendages called parapodia, which help in swimming. Chitinous setae in Earthworms, and suckers in Leech help in locomotion. The circulatory system is of closed type and the respiratory pigments are haemoglobin and chlorocruorin.

Nervous system consists of paired ganglion connected by the lateral nerves to the double ventral nerve cord. They reproduce sexually. Development is direct or indirect and includes a trochophore larva. Some are monoecious (earthworms) while some are dioecious (Neries and Leech). (Figure 2.14) Examples: Lampito mauritii (earthworm), Neries (sand worm), Hirudinaria (leech).

Phylum: Arthropoda

(G. arthros – jointed; podes – feet)

This is the largest phylum of the Kingdom Animalia and includes the largest class called insecta (total species ranges from 2-10 million). They are bilaterally symmetrical, segmented, triploblastic and schizocoelomate animals with organ system grade of body organisation.

They have jointed appendages which are used for locomotion, feeding and are sensory in function. Body is covered by chitinous exoskeleton for protection and to prevent water loss, It is shed of periodically by a process called moulting or ecdysis. The body consists of a head, thorax, and abdomen with a body cavity called haemocoel. Respiratory organs are gills, book gills, book lungs and trachea.

Circulatory system is of open type. Sensory organs like antennae, eyes (compound and simple), statocysts (organs of balance/ equilibrium) are present. Excretion takes place through malpighian tubules, green glands, coxal glands, etc.

They are mostly dioecious and oviparous; fertilization is usually internal. Development may be direct or indirect. Life history includes many larval stages followed by metamorphosis. Examples: Limulus (King crab, a living fossil), Palamnaeus (Scorpion), Eupagarus (Hermit crab), Apis (Honey bee), Musca (House fly), Vectors – Anopheles, Culex, Aedes (mosquitoes), Economically important insects – Apis – (Honey bee), Bombyx (Silk worm), Laccifer (Lac insects), Gregarious pest – Locusta (Locust) (Figure 2.15)

Phylum: Mollusca (L. molluscs – soft bodied)

This is the second largest animal phylum. Molluscs are terrestrial and aquatic (marine or fresh water) and exhibit organ system level of body organisation. They are bilaterally symmetrical (except univalves eg. apple snail) triploblastic and coelomate animals. Body is covered by a calcareous shell and is unsegmented with a distinct head, muscular foot and a visceral hump or visceral mass.

A soft layer of skin forms a mantle over the visceral hump. The space between the visceral mass and mantle (pallium) is called the mantle cavity in which a number of feather like gills (ctenidia) are present, which are respiratory in function.

The digestive system is complete and mouth contains a rasping organ called radula with transverse rows of chitinous teeth for feeding (radula is absent in bivalves). The sense organs are tentacles, eyes and osphraidium (to test the purity of water and present in bivalves and gastropods).

Excretory organs are nephridia. Open type of circulatory system is seen except for cephalopods such as squids, cuttle fishes and octopus. Blood contains haemocyanin, a copper containing respiratory pigment. They are dioecious and oviparous. Development is indirect with a veliger larva (a modifid trochophore larva). Examples: Pila (Apple snail), Lamellidens (Mussel), Pinctada (Pearl oyster), Sepia (Cuttle fish), Loligo (Squid), Octopus (Devil fish) (Figure 2.16).

Phylum Echinodermata

(G. Echinos – spiny; dermos – skin)

All Echinoderms are marine animals. The adults are radially symmetrical but the larvae are bilaterally symmetrical. These animals have a mesodermal endoskeleton of calcareous ossicles and hence the name Echinodermata (spiny skin).

They are exclusively marine with organ system level of organisation. The most distinctive feature of echinoderms is the presence of the water vascular system or ambulacral system with tube feet or podia, which helps in locomotion, capture and transport of food and respiration.

The digestive system is complete with mouth on ventral side and anus on the dorsal side. Excretory organs are absent. The nervous system and sensory organs are poorly developed. The circulatory system is open type without heart and blood vessels.

Sexes are separate. Reproduction is sexual and fertilization is external. Development is indirect with free swimming bilaterally symmetrical larval forms. Some echinoderms exhibit autotomy with remarkable powers of regeneration. e.g. Star fish. (Figure 2.17) Examples: Asterias (Starfish or Sea star), Echinus (Sea-urchin), Antedon (Sealily), Cucumaria (Sea-cucumber), Ophiura (Brittle star).

Phylum: Hemichordata

(G.hemi –half; chorda-string)

Hemichordates were earlier treated as a subphylum of Chordata (or Prochordata). They are now regarded to be an independent phylum of invertebrates, close to Echinodermata. The animals of this group possess the characters of invertebrates as well as chordates.

This phylum consists of a small group of worm-like, soft marine animals, mostly tubiculous and commonly called the ‘acorn worms’ or ‘tongue worms’. They are bilaterally symmetrical, triploblastic and coelomate animals with organ system level of organisation. Their body is cylindrical and is divided into three regions, the anterior proboscis, a short collar and a long trunk.

Most hemichordates are ciliary feeders. Their circulatory system is simple and open or lacune type with a dorsal heart. Respiration is through paired gill slits opening into the pharynx. Excretion is by a single proboscis gland or glomerulus situated in the proboscis.

Nervous system is primitive. Sexes are separate and exhibit sexual mode of reproduction; Fertilization is external. Development is indirect with a free swimming tornaria larva. Examples: Balanoglossus, Saccoglossus, Ptychodera flava (Indian Hemichordate found in Kurusadai islands in Tamilnadu). (Figure 2.18).

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Classification of Kingdom Animalia

Animal kingdom is divided into two sub-kingdoms, the Parazoa and Eumetazoa based on their organisation.

1. Parazoa:

These include the multicellular sponges and their cells are loosely aggregated and do not form tissues or organs.

2. Eumetazoa:

These include multicellular animals with well defined tissues, which are organised as organs and organ systems. Eumetazoans includes two taxonomic levels called grades. They include Radiata and Bilateria.

Grade 1: Radiata

Among the eumetazoa, a few animals have an organisation of two layers of cells, the outer ectoderm and inner endoderm, separated by a jelly like mesoglea. They are radially symmetrical and are diploblastic. Examples: Cnidarians (sea anemone, jelly fish) and Ctenophores (comb jellies).

Grade 2: Bilateria

The eumetazoans other than Radiata, show organ level of organisation and are bilaterally symmetrical and triploblastic. The grade Bilateria includes two taxonomic levels called Division.

Division 1: Protostomia (Proto: first; stomium: mouth)

Protostomia includes the eumetazoans in which the embryonic blastopore develops into mouth. This division includes three subdivisions namely acoelomata, pseudocoelomata and schizocoelomata.

Division 2: Deuterostomia (deuteron: secondary; stomium: mouth)

Eumetazoans in which anus is formed from or near the blastopore and the mouth is formed away from the blastopore. It includes only one subdivision Enterocoelomata. They have a true coelom called enterocoel, formed from the archenteron.

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Basis of Classification

Multicellular organisms are structurally and functionally different but yet they possess certain common fundamental features such as the arrangement of cell layers, the levels of organisation, nature of coelom, the presence or absence of segmentation, notochord and the organisation of the organ system.

Levels of Organisation

All members of Kingdom Animalia are metazoans (multicellular animals) and exhibit different patterns of cellular organisation. The cells of the metazoans are not capable of independent existence and exhibit division of labour. Among the metazoans, cells may be functionally isolated or similar kinds of cells may be grouped together to form tissues, organ and organ systems.

Cellular Level of Organisation

This basic level of organisation is seen in sponges. The cells in the sponges are arranged as loose aggregates and do not form tissues, i.e. they exhibit cellular level of organisation. There is division of labour among the cells and different types of cells are functionally isolated.

In sponges, the outer layer is formed of pinacocytes (platelike cells that maintain the size and structure of the sponge) and the inner layer is formed of choanocytes. These are flagellated collar cells that create and maintain water flow through the sponge thus facilitating respiratory and digestive functions.

Tissue Level of Organisation

In some animals, cells that perform similar functions are aggregated to form tissues. The cells of a tissue integrate in a highly coordinated fashion to perform a common function, due to the presence of nerve cells and sensory cells. This tissue level of organisation is exhibited in diploblastic animals like cnidarians. The formation of tissues is the first step towards evolution of body plan in animals (Hydra – Coelenterata).

Organ Level of Organisation

Different kinds of tissues aggregate to form an organ to perform a specific function. Organ level of organisation is a further advancement over the tissue level of organisation and appears for the first time in the Phylum Platyhelminthes and seen in other higher phyla.

Organ System Level of Organisation

The most efficient and highest level of organisation among the animals is exhibited by flatworms, nematodes, annelids, arthropods, molluscs, echinoderms and chordates. The evolution of mesoderm in these animals has led to their structural complexity. The tissues are organised to form organs and organ systems. Each system is associated with a specific function and show organ system level of organisation.

Highly specialized nerve and sensory cells coordinate and integrate the functions of the organ systems, which can be very primitive and simple or complex depending on the individual animal. For example, the digestive system of Platyhelminthes has only a single opening to the exterior which serves as both mouth and anus, and hence called an incomplete digestive system. From Aschelminthes to Chordates, all animals have a complete digestive system with two openings, the mouth and the anus.

Similarly, the circulatory system is of two types, the open type: in which the blood remains filled in tissue spaces due to the absence of blood capillaries. (arthropods, molluscs, echinoderms and urochordates) and the closed type: in which the blood is circulated through blood vessels of varying diameters (arteries, veins and capillaries) as in annelids, cephalochordates and vertebrates.

Diploblastic and Triploblastic Organisation

During embryonic development, the tissues and organs of animals originate from two or three embryonic germ layers. On the basis of the origin and development, animals are classified into two categories: Diploblastic and Triploblastic.

Animals in which the cells are arranged in two embryonic layers (Figure 2.1), the external ectoderm, and internal endoderm are called diploblastic animals. In these animals the ectoderm gives rise to the epidermis (the outer layer of the body wall) and endoderm gives rise to gastrodermis (tissue lining the gut cavity). An undiffrentiated layer present between the ectoderm and endoderm is the mesoglea. (Corals, Jellyfih, Sea anemone)

Animals in which the developing embryo has three germinal layers are called triploblastic animals and consists of outer ectoderm (skin, hair, neuron, nail, teeth, etc), inner endoderm (gut, lung, liver) and middle mesoderm (muscle, bone, heart). Most of the triploblastic animals show organ system level of organisation (Flat worms to Chordates).

Patterns of Symmetry

Symmetry is the body arrangement in which parts that lie on opposite side of an axis are identical. An animal’s body plan results from the animal’s pattern of development. The simplest body plan is seen in sponges (Figure 2.2).

They do not display symmetry and are asymmetryical. Such animals lack a definite body plan or are irregular shaped and any plane passing through the centre of the body does not divide them into two equal halves (Sponges). An asymmetrical body plan is also seen in adult gastropods (snails).

Symmetrical animals have paired body parts that are arranged on either side of a plane passing through the central axis. When any plane passing through the central axis of the body divides an organism into two identical parts, it is called radial symmetry.

Such radially symmetrical animals have a top and bottom side but no dorsal (back) and ventral (abdomen) side, no right and left side. They have a body plan in which the body parts are organised in a circle around an axis. It is the principal symmetry in diploblastic animals. Cnidarians such as sea anemone and corals (Figure 2.3) are radially symmetrical.

However, triploblastic animals like echinoderms (e.g., starfish) have five planes of symmetry and show Pentamerous radial symmetry. Animals which possess two pairs of symmetrical sides are said to be biradially symmetrical (Figure 2.4).

Biradial symmetry is a combination of radial and bilateral symmetry as seen in ctenophores. There are only two planes of symmetry, one through the longitudinal and sagittal axis and the other through the longitudinal and transverse axis. (e.g., Comb jellyfish – Pleurobrachia)

Animals which have two similar halves on either side of the central plane show bilateral symmetry (Figure 2.5). It is an advantageous type of symmetry in triploblastic animals, which helps in seeking food, locating mates and escaping from predators more efficiently. Animals that have dorsal and ventral sides, anterior and posterior ends, right and left sides are bilaterally symmetrical and exhibit cephalisation, in which the sensory and brain structures are concentrated at the anterior end of the animal.

Coelom

The presence of body cavity or coelom is important in classifying animals. Most animals possess a body cavity between the body wall and the alimentary canal, and is lined with mesoderm (Figure 2.6)

Animals which do not possess a body cavity are called acoelomates. Since there is no body cavity in these animals their body is solid without a perivisceral cavity, this restricts the free movement of internal organs. (e.g., Flatworms)

In some animals, the body cavity is not fully lined by the mesodermal epithelium, but the mesoderm is formed as scattered pouches between the ectoderm and endoderm. Such a body cavity is called a pseudocoel and is filed with pseudocoelomic fluid.

Animals that possess a pseudocoel are called pseudocoelomates e.g., Round worms. The pseudocoelomic fluid in the pseudocoelom acts as a hydrostatic skeleton and allows free movement of the visceral organs and for circulation of nutrients.

Eucoelom or true coelom is a fluidfilled cavity that develops within the mesoderm and is lined by mesodermal epithelium called peritoneum. Such animals with a true body cavity are called coelomates or eucoelomates.

Based on the mode of formation of coelom, the eucoelomates are classified into two types, Schizocoelomates – in these animals the body cavity is formed by splitting of mesoderm. (e.g., annelids, arthropods, molluscs). In Enterocoelomate animals the body cavity is formed from the mesodermal pouches of archenteron. (e.g., Echinoderms, hemichordates and chordates) (Figure 2.7).

Segmentation and Notochord

In some animals, the body is externally and internally divided into a series of repeated units called segments with a serial repetition of some organs (Metamerism). The simplest form of segmentation is found in Annelids in which each unit of the body is very similar to the next one. But in arthropods (cockroach), the segments may look different and has different functions.

Animals which possess notochord at any stage of their development are called chordates. Notochord is a mesodermally derived rod like structure formed on the dorsal side during embryonic development in some animals. Based on the presence or absence of notochord, animals are classified as chordates (Cephalochordates, Urochordates, Pisces to Mammalia) and nonchordates (Porifera to Hemichordata).

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Tools for Study of Taxonomy

Tools and taxonomical aids may be different for the study of plants and animals. Herbarium and Botanical garden may be used as tools for the study of plant taxonomy. In the case of animal studies, the classical tools are Museum, Taxonomical Keys and Zoological and Marine parks.

The important components of the taxonomical tools are field visits, survey, identifiation, classification, preservation and documentation. Many tools are being used for taxonomical studies, amongst them some of the important tools are discussed below:

The Classical Taxonomical Tools

Taxonomical Keys:

Keys are based on comparative analysis of the similarities and dissimilarities of organisms. There are separate keys for different taxonomic categories.

Museum:

Biological museums have collection of preserved plants and animals for study and ready reference. Specimens of both extinct and living organisms can be studied.

Zoological Parks:

These are places where wild animals are kept in protected environments under human care. It enables us to study their food habits and behaviour.

Marine Parks:

Marine organisms are maintained in protected enviroments. Printed taxonomical tools consist of identifiation cards, description, field guides and manuals.

Molecular Taxonomical Tools

Technological advancement has helped to evolve molecular taxonomical tools from classical tools to molecular tools. The accuracy and authenticity is more significant in the molecular tools. The following methods are being used for taxonomical classification.

Molecular techniques and approaches such as DNA barcoding (short genetic marker in an organism’s DNA to identify it as belonging to a particular species), DNA hybridization (measures the degree of genetic similarity between pools of DNA sequences), DNA fingerprinting (to identify an individual from a sample of DNA by looking at unique patterns in their DNA).

Restriction Fragment Length Polymorphisms (RFLP) analysis (difference in homologous DNA sequences that can be detected by the presence of fragments of different lengths after digestion of the DNA samples), and Polymerase Chain Reaction (PCR) sequencing (to amplify a specific gene, or portion of gene) are used as taxonomical tools.

Automated Species Identifiation Tools

It consists of Cyber tools. For example:
ALIS, DAISY, ABIS, SPIDA, Draw wing, etc.

ALIS → Automated Leafhpper Identifiation System.
DAISY → Digital Automated Identifiation System.
ABIS → Automatic Bee Identifiation System.
SPIDA → Species Identifid Automatically (spiders, wasp and bee wing characters).
Draw wing → Honey bee wing identifiation.

Neo Taxonomical Tools:

This is based on Electron Microscopy images to study the molecular structures of cell organelles.

Ethology of Taxonomical Tools:

Based on the behaviour of the organisms it can be classified. For example sound of birds, bioluminescence, etc.

e-Taxonomic Resources:

INOTAXA is an electronic resource for digital images and description about the species which was developed by Natural History Museum, London. INOTAXA means Integrated Open taxonomic Access.

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Concept of Species

Species is the basic unit of classification. The term species was coined by John Ray, and in his book “Historia Generalis Plantarum” (3 volumes) in 1693 described species as a group of morphologically similar organisms arising from a common ancestor. Carolus Linnaeus in his book “Systema naturae” considered species as the basic unit of classification.

Species can be defined as a group of organisms that have similar morphology and physiology and can interbreed to produce fertile offsprings. In 1859 Charles Darwin in his book Origin of species explains the evolutionary connection of species by the process of natural selection.

The concept of species is an important but difficult one in biology, and is sometimes referred to the “species problem”. Some major species concepts are: Typological (or Essentialist, Morphological, Phenetic) species concept. Typology is based on morphology/phenotype.

Linnaeus (1707-1778), nearly 50 years later whose work was the most eminent and momentous in the taxonomy field, adopting a broader concept gave a new definition of species.

The biological species concept relies on behavioral data and emphasizes reproductive isolation between groups. The lineage species concept relies on genetic data and emphasizes distinct evolutionary trajectories between groups, which result in distinct lineages (branches on a phylogenetic tree).

Typological or Essentialist Species

Concept 2. Nominalistic Species
Concept 3. Biological Species
Concept 4. Evolutionary Species

Although the biological species concept has long been accepted by many evolutionary biologists (especially zoologists) as the best species concept, these kinds of problems have led to increasing attacks.

The natural world contains about 8.7 million species, according to a new estimate described by scientists as the most accurate ever. But the vast majority have not been identified – and cataloguing them all could take more than 1,000 years.

Organisms may appear to be alike and be different species. For example, Western meadowlarks (Sturnella neglecta) and Eastern meadowlarks (Sturnella magna) look almost identical to one another, yet do not interbreed with each other – thus, they are separate species according to this definition.

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Three Domains of Life

Three domain classification was proposed by Carl Woese (1977) and his co-workers. They classified organisms based on the difference in 16S rRNA genes. The three domain system adds the taxon ‘domain’ higher than the kingdom.

This system emphasizes the separation of Prokaryotes into two domains, Bacteria and Archaea, and all the eukaryotes are placed into the domain Eukarya. Archaea appears to have more in common with the Eukarya than the Bacteria. Archaea differ from bacteria in cell wall composition and differs from bacteria and eukaryotes in membrane composition and rRNA types.

1. Domain Archaea

This domain includes single celled organisms, the prokaryotes which have the ability to grow in extreme conditions like volcano vents, hot springs and polar ice caps, hence are also called extremophiles. They are capable of synthesizing their food without sunlight and oxygen by utilizing hydrogen sulphide and other chemicals from the volcanic vents. Some of the them produced methane (methanogens), few live in salty environments (Halophiles) and are thermoacidophiles which thrive in acidic environments and at high temperatures.

2. Domain Bacteria

Bacteria are prokaryotic, their cells have no definite nucleus and DNA exists as a circular chromosomes and do not have histones associated with it. They do not possess membrane bound organelles except for ribosome (70S type). Their cell wall contains peptidoglycans.

Many are decomposers, some are photosynthesizers and few cause diseases. There are beneficial probiotic bacteria and harmful pathogenic bacteria which are diversely populated. Cyanobacteria are photosynthetic blue green algae which produce oxygen. These had played a key role in the changes of atmospheric oxygen levels from anaerobic to aerobic during the early geologic periods.

3. Domain Eukarya (Eukaryotes)

Eukaryotes are animals which have true nucleus and membrane bound organelles. DNA in the nucleus is arranged as a linear chromosome with histone proteins, ribsosomes of 80S type in the cytosol and 70S type in the chloroplast and mitochondria. Organisms in this domain are classified under kingdoms, namely, Protista, Fungi, Plantae and Animalia.

In 1987, Cavalier-Smith revised the six kingdom system to Seven Kingdom system. The concept of super kingdom was introduced and revised to seven kingdom classification. The classifiation is divided into two Super Kingdoms (Prokaryota and Eukaryota) and seven kingdoms, two Prokaryotic Kingdoms (Eubacteria and Archaebacteria) and five Eukaryotic Kingdoms (Protozoa, Chromista, Fungi, Plantae and Animalia). (Table 1.1).

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Diversity in the Living World

Earth has numerous habitats with a wide range of living organisms inhabiting them. Plants and animals are present in almost all the places, from polar icecaps to volcanic hot springs, from shallow lagoons to the deepest oceans, from tropical rain forests to dry and parched deserts. There are a variety of species that have been adapted successfully to live in diverse ecosystems.

Ecosystem is a community of biotic and a biotic factors and their interrelationships (A.G. Tansley, 1935). The presence of a large number of species in a particular ecosystem is called ‘biological diversity’ or in short ‘biodiversity’. The term biodiversity was first introduced by Walter Rosen (1985), and defined by E.D. Wilson.

Characterstic Features of Living Organisms

Living organisms show a variety of unique characters different from nonliving matter. The key characters of living organisms are, cellular organization, nutrition, respiration, metabolism, growth, response to stimuli, movement, reproduction, excretion, adaptation and homeostasis.

Numerous scientists and taxonomists have made tremendous contribution and documentation in the observation and study of even minute characters in living organisms. Their keen observations have led to the classification of living organisms and the study of their interrelationships.

Increase in mass and increase in number of individuals are essential criterion for the growth of the living organism. Growth of multicellular organisms occurs due to cell division. Reproduction is another characteristic of living organisms. Metabolism is another characteristic of living organisms.

Diverse form of living organisms are found in different types of habitats like ocean, fresh water bodies, forests, cold mountains, deserts, hot water springs etc.

Biodiversity is the variation of life forms, within a given ecosystem, biome or for the entire earth. It is a combination of two words; bio meaning life and diversity meaning variety. It refers to the varieties of plants,
animals and micro-organisms, the genes they contain and the ecosystems they form.

It means understanding that each individual is unique, and recognizing our individual differences. These can be along the dimensions of race, ethnicity, gender, sexual orientation, socio-economic status, age, physical abilities, religious beliefs, political beliefs, or other ideologies.

‘Living’ is something that is alive, something that can grow, move, reproduce, respire and carry out various cellular activities.

Diversity gives you access to a greater range of talent, not just the talent that belongs to a particular world-view or ethnicity or some other restricting definition. It helps provide insight into the needs and motivations of all of your client or customer base, rather than just a small part of it.

The term biodiversity (from “biological diversity”) refers to the variety of life on Earth at all its levels, from genes to ecosystems, and can encompass the evolutionary, ecological, and cultural processes that sustain life.

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Environmental Issues of Ecosan Toilets

About 150 liters of wastewater at an average is generated by an Indian individual daily, and a large amount of it is generated from toilets. Ecological sanitation (EcoSan) is a sustainable system for handling human excreta by using dry composting toilets.

EcoSan toilets not only reduce wastewater generation but also generate the natural fertilizer from recycled human excreta, which forms an excellent substitute for chemical fertilizers. This method is based on the principle of recovery and recycling of nutrients from excreta to create a valuable supply for agriculture.
‘EcoSan’ toilets are being used in several parts of India and Sri Lanka.

Eco-San is a specially formulated food contact surface sanitizer and destainer for use in low-temperature warewashing machines that rinses clear. Eco-San leaves dishes, flatware and glassware both sparkling and hygienically clean, as it combats a broad spectrum of organisms.

The EcoSan toilet is a closed system that does not need water, so is an alternative to leach pit toilets in places where water is scarce or where the water table is high and the risk of groundwater contamination is increased. When the pit of an EcoSan toilet fills up it is closed and sealed.

It is being used in Gulbarga, Karnataka. A self flushing e-toilet (using concept of pay & use toilet scheme) are toilets that are designed in such a way that it flushes itself on entry and exit with a drop of coin. They are
prevalent in Delhi, Kerala and Mumbai for footpath and slum dwellers.

Wherever the Need, an NGO in the UK build ecosan facilities (UDDTs) in various parts of the developing world. They predominantly work in Tamil Nadu (India), where the Tamil Nadu State Government
provides subsidies for their work.

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Solid Waste Management

Every day, tonnes of solid wastes are disposed off at landfill sites. This waste comes from homes, offices, industries and various other agricultural related activities. These landfill sites produce foul smell if waste is not stored and treated properly.

When hazardous wastes like pesticides, batteries containing lead, cadmium, mercury or zinc, cleaning solvents, radioactive materials, e-waste and plastics are mixed up with paper and other scraps and burnt, they produce gases such as dioxins. These gases are toxic and carcinogenic. These pollute the surrounding air, ground water and can seriously affect the health of humans, wildlife and our environment (Table 12.1).

Solid Waste management includes the activities and actions required to manage waste from its inception to its final disposal. This includes the collection, transport, treatment and disposal of waste, together with monitoring and regulation of the waste management process. It is all about how solid waste can be changed and used as a valuable resource.

Case Study:

The Corporation of Chennai looks after clearance and management of solid waste in Chennai. Every day around 5400 Metric Tonnes (MT) of garbage is collected from the city. Door to door collection of garbage is done in most zones apart from sweeping, collecting, and storing the waste in the specified bins.

At present garbage generated in Chennai is dumped at two sites. Proposals are there for remediation of the existing landfill or scientific closure and to have integrated waste processing facilities with waste to energy plants as one of the components at the existing Kodungaiyur and Perungudi sites.

Waste Management Practices

• Source segregation
• Composting
• Aerobic
• Anaerobic
• Vermicomposting
• Biogas generation
• Incineration

Radioactive Waste

Radioactive wastes are generated during various operations of the nuclear power plant. Radioactive waste can be in gas, liquid or solid form, and its level of radioactivity can vary. The waste can remain radioactive for a few hours or several months or even hundreds of thousands of years. Depending on the level and nature of radioactivity, radioactive wastes can be classified as exempt waste, Low and Intermediate level waste and High Level Waste.

Radioactive Waste Management

Radioactive waste management involves the treatment, storage, and disposal of liquid, airborne, and solid effluents from the nuclear industry.

Methods of Disposal of Radioactive Wastes are

1. Limit Generation:

Limiting the generation of waste is the first and most important consideration in managing radioactive wastes.

2. Dilute and Disperse:

For wastes having low radioactivity, dilution and dispersion are adopted.

3. Delay and Decay:

Delay and decay is frequently an important strategy because much of the radioactivity in nuclear reactors and accelerators is very short lived.

4. Concentrate and Confie Process:

Concentrating and containing is the objective of treatment activities for longerlived radioactivity. The waste is contained in corrosion resistant containers and transported to disposal sites. Leaching of heavy metals and radionuclides from these sites is a problem of growing concern.

Control and Management
Three ways are employed to manage nuclear wastes.

Spent Fuel Pools:

The spent fuel discharged from the reactors is temporarily stored in the reactor pool. The Spent fuel rods are used in stored cooling ponds. They protect the surroundings from radiation and absorb the heat generated during radioactive decay.

Vitrification Method:

This prevents reaction or degradation of nuclear waste for extended periods of time and encased in dry cement caskets.

Geological Repositories:

A deep geological repository is a nuclear waste repository excavated deep within a stable geologic environment. It is suited to provide a high level of long-term isolation and containment without future maintenance. In India at Tarapur and Kalpakkam, a wet storage facility of Spent Fuel is the main mode of storage.

Medical Waste

Any kind of waste that contains infectious material generated by hospitals, laboratories, medical research centers, Pharmaceutical companies and Veterinary clinics are called medical wastes.

Medical wastes contain body fluids like blood, urine, body parts and other contaminants, culture dishes, glasswares, bandages, gloves, discarded needles, scalpels, swabs and tissues.

Management:

The safe and sustainable management of biomedical waste is the social and legal responsibilities of people working in healthcare centers.

Waste Disposal:

Involved by incineration, chemical disinfection, autoclaving, encapsulation, microwave irradiation are methods of waste disposals. Final disposal includes landfill and burying as per norms inside premises.

E-Waste

Electronic waste or e-waste describes discarded electrical electronic devices as well as any refuse created by discarded electronic devices and components and substances involved in their manufacture or use. Their disposal is a growing problem because electronic equipment frequently contains hazardous substances.

In a personal computer, for example, there may be lead (Pb) in the cathode ray tube (CRT) and soldering compound, mercury (Hg) in switches and housing, and cobalt (Co) in steel components, among other equally
toxic substances. E-wastes are basically PCB (Polychlorinated biphenyl) based, which are non-degradable (Fig.12.8).

Used electronics which are destined for reuse, resale, salvage, recycling, or disposal are also considered e-waste. Unauthorised processing of e-waste in developing countries can lead to adverse human health effects and environmental pollution.

Recycling and disposal of e-waste may involve significant risk to the health of workers and communities in developed countries and great care must be taken to avoid unsafe exposure in recycling operations and leaking of materials such as heavy metals from landfills and incinerator ashes.

Plastic Waste – Solutions and Remedies

Plastics are low molecular weight organic polymers that are non-degradable in the natural environment. They are used in several items, including cars, bulletproof vests, toys, hospital equipment, carry bags and food containers.

Packaging materials used in supermarkets, retail outlets, manufacturing industries, households, hotels, hospitals, restaurants and transport companies are major contributors to plastic waste generation. Plastic waste constitutes a major part of municipal solid waste.

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Organic Farming and its Implementation

It is a method of farming system which primarily aims at cultivating the land and raising crops in such a way, so as to keep the soil alive and in good health by use of organic wastes (crop, animal and farm wastes, aquatic wastes) and other biological materials along with beneficial microbes (biofertilizers) to release nutrients to crops for increased sustainable production in an eco-friendly pollution free environment.

organic farming systems by the farmers in the following ways:

• The selection of locations not contaminated with chemicals
• Appropriate local types of rice plant
• Programming of appropriate crop rotation
• Processing soil with tools not contaminated with chemicals
• Intermitten irrigation
• Use of

Organic agriculture can be defined as “an integrated farming system that strives for sustainability, the enhancement of soil fertility and biological diversity while, with rare exceptions, prohibiting synthetic pesticides, antibiotics, synthetic fertilizers, genetically modified organisms, and growth hormones”.

Organic agriculture considers the medium- and long-term effect of agricultural interventions on the agro-ecosystem. It aims to produce food while establishing an ecological balance to prevent soil fertility or pest problems.

Advantages of Organic Farming

• Minimises the external cost of farming.
• Efficient use of resources.
• Soil and the environment is a public good.
• Healthier food.
• Healthier animals.
• Potential profits.
• Time involved.
• More labour intensive.

Organic farming eliminates the use of synthetic products to maximize the yields that can be produced. It works on creating a healthier soil instead, encouraging the link between healthy plants and protected soils. No chemical herbicides or pesticides are used. Only natural soil enhancement techniques are permitted.

There are basically two types of organic farming: pure organic farming and integrated organic farming. With pure organic farming, the method includes the use of manures and biopesticides with complete avoidance of inorganic chemicals and pesticides.

In the process of pure farming, fertilizer and pesticides obtain from natural sources. It is called a pure form of organic farming. (b) Integrated organic farming – Integrated organic farming consists of integrated nutrients management and integrated pest management.

In a few words, organic farming involves growing techniques and methods that seek to protect the environment, humans, and animals, through sustainable agriculture. As fertilization methods, they mainly use manure, compost, or special organic synthetic fertilizers.

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Eutrophication | Definition, Types, Causes, & Effects

When run-off from land containing nutrients reaches water bodies like lakes, it results in dense growth of plant life. This phenomenon is called Eutrophication. Natural aging of lakes also leads to nutrient enrichment of its water.

In a lake, the water is cold and clear (oligotrophic stage), supporting little life. With time, streams draining into the lake introduce nutrients such as nitrates and phosphates, which encourage the growth of aquatic organisms. Aquatic plants and animal life grow rapidly, and organic remains begin to be deposited on the lake bottom (mesotrophic stage) (Fig. 12.5).

Pollutants from anthropogenic activities like effluents from the industries and homes can radically accelerate the aging process. This phenomenon is known as Cultural or Accelerated Eutrophication.

Nutrients stimulate the growth of algae, water hyacinth and can cause clogging of canals, rivers and lakes as well as, displacing native plants. It causes unsightly foam and unpleasant odours, and deprives the water of dissolved oxygen.

Integrated Wastewater Management

Wastewater Treatment

Wastewater or sewage originates from domestic waste waters, industrial wastes and animal wastes. Realizing the importance of clean potable water, the Government passed the Water (Prevention and Control of Pollution) Act in 1974, which made it mandatory to treat wastewater in treatment plants. The main objective of a wastewater treatment process is to reduce organic and inorganic components in wastewater to a level that it no longer supports microbial growth and to eliminate other potentially toxic materials.

Microorganisms mainly bacteria and some protozoa play an essential part in the treatment of sewage to make it harmless. Sewage contains pathogenic bacteria. These bacteria must be destroyed in order to prevent the spread of diseases. Sewage treatment is usually performed in the following three stages (Fig. 12.6).

Primary treatment

Primary treatment involves the physical removal of solid and particulate organic and inorganic materials from the sewage through filtration and sedimentation. Floating debris is removed by sequential filtration. Then the grit (soil and small pebbles) are removed by sedimentation. All solids that settle form the primary sludge and the supernatant forms the effluent. The effluent from the primary settling tank is taken for secondary treatment.

Secondary treatment or biological treatment

The primary effluent is passed into large aeration tanks where it is constantly agitated mechanically and air is pumped into it. This allows vigorous growth of useful aerobic microbes into floc (masses of bacteria associated with fungal fiaments to form mesh like structures).

While growing, these microbes consume the major part of the organic matter in the effluent. This significantly reduces the BOD (Biochemical oxygen demand or Biological oxygen demand). BOD refers to the amount of the oxygen that would be consumed, if all the organic matter in one litre of water were oxidized by bacteria. The sewage water is treated till the BOD is reduced. The greater the BOD of the waste water more is its polluting potential.

Once the BOD of sewage water is reduced signifiantly, the effluent is then passed into a settling tank where the bacterial “flocs” are allowed to sediment. This sediment is called activated sludge. A small part of activated sludge is pumped back into the aeration tank to serve as the inoculum. The remaining major part of the sludge is pumped into large tanks called anaerobic sludge digesters. Here, the bacteria which grow anaerobically, digest the bacteria and the fungi in the sludge. During this digestion, bacteria produce a mixture of gases such as methane, hydrogen sulphide and CO₂. These gases form biogas and can be used as a source of energy.

Tertiary treatment

Tertiary treatment is the final process that improves the quality of the waste water before it is reused, recycled or released into natural water bodies. This treatment removes the remaining inorganic compounds and substances, such as nitrogen and phosphorus.

UV is an ideal disinfectant for wastewater since it does not alter the water quality – except for inactivating microorganisms. UV is a chemicalfree process that can completely replace the existing chlorination system and also inactivates chlorine-resistant microorganisms like Cryptosporidium and Giardia.

Case Study:

Auroville, located in South India near Puducherry has been experimenting with natural wastewater recycling systems (Decentralized Waste Water Treatment System (DEWATS)) (Fig.12.7a). Such treatment plants have now also been implemented in Aravind Eye Hospital, Puducherry (Root Zone Wastewater Treatment (RZWT)) (Fig.12.7 b) and the Chennai Mathematical Institute, Siruseri IT Park, Chennai.