Unit 1: Unit 1: Biodiversity & Classification — Short Questions

Three Domains of Life
• In 1990, American microbiologist Carl Woese classified living organisms into three domains i.e., domain Archaea, domain Bacteria and domain Eukarya.
• According to his three-domain system, domain Archaea and domain Bacteria contain prokaryotes but they differ in a number of features.

Cell structure
i. Archaea: They are prokaryotes, lacking membrane bounded organelles and true nucleus. Their cell membrane contains lipids with ether-linkage between glycerol and fatty acid chains.
ii. Bacteria: Like archaea, bacteria possess prokaryotic cell i.e., lack a true nucleus and membrane-bound organelles. Cell membrane have lipids with fatty acids attached to glycerol by ester linkages.
iii. Eukarya: They possess eukaryotic cells - with true nucleus enclosed by a nuclear membrane. Cells have membrane-bounded organelles e.g., mitochondria, chloroplasts.

Key feature A key feature differentiating Archaea from Bacteria is the structure of their cell walls. The cell walls of archaea lack cellulose and peptidoglycan. Instead, they contain distinct polysaccharides and proteins. Some archaea have pseudopeptidoglycan. On the other hand, bacterial cell walls contain peptidoglycan, a polymer consisting of sugars and amino acids that provides structural support.

Kingdom fungi is characterized by organisms which possess chitin (a polysaccharide) in their cell walls. They are called decomposers as they follow absorptive mode of nutrition and do not ingest food like other animals.
Examples: mushrooms, rusts, smuts and molds.

Allopatric speciation occurs when populations are geographically separated. These groups experience different environments and evolve independently. Over time, the accumulated differences can become significant enough to prevent interbreeding, even if the geographical barrier is removed.
Example: Speciation observed in Darwin's finches on the Galápagos Islands, where different populations adapted to diverse environments.

Genetic drift means change in the frequency of alleles at a locus in small population that occurs by chance. It plays important role in speciation by causing genetic divergence and creating new species.

Transect sampling is the primary and effective method used to assess species distribution across different conditions. It involves laying out a line or strip (transect) across the study area and recording species at regular intervals along this line.
Example: In a coastal zone, a transect can be laid from the high tide line to the low tide line, to record the types and abundance of intertidal organisms.

Ecosystem level involves in evaluation of variety of ecosystems in a region. Because at this level, biodiversity assessment includes the range of habitats from forests and wetlands to grasslands and deserts. It involves understanding how different ecosystems function and how they contribute to overall ecological health.

Phylogeny The evolutionary relationship among the organisms is called phylogeny.
Phylogenetic tree: The diagram which shows phylogeny is called phylogenetic tree or also termed as evolutionary tree.

Woese proposed the three-domain system based on molecular evidence showing that prokaryotes are not a monophyletic group rather there are two separate groups of prokaryotes i.e. Archea and Bacteria.
Unlike Whittaker's five-kingdom system (which grouped all prokaryotes into Monera). Woese divided prokaryotes in two separate domains with Eukarya as the third domain.

Evidences Archaea share genetic sequences and the regulatory mechanisms with Eukarya, which are absent in Bacteria. This genetic similarity indicates that Archaea are more closely related to Eukarya than to Bacteria.

Domain In biological taxonomic hierarchy, the highest rank/ level of classification is termed as Domain (also called super kingdom).
In 1990 American microbiologist Carl Woese suggested that there are two separate groups of Prokaryotes, and classified living organisms into three domains.
i. Domain Archaea
ii. Domain Bacteria
iii. Domain Eukarya

Individual archaeans range from 0.1 μm to 15μm in diameter, some form aggregates or filament upto 200 μm in length.
Reproduction: Archea reproduce asexually by binary or multiple fission, fragmentation or budding. Mitosis and meiosis don't occur in archaea.

Cell Membrane
• The cell membrane of archaeans contain lipids with ether linkage between glycerol and fatty acid chains. While that of eukaryans and bacterial membrane lipids with ester-linkages between glycerol and fatty acid chains.
• Archaean fatty acid chains branched while that of eukaryans and bacterial are unbranched.

Ans. [See figure with diagrams showing Archaean membrane lipid structure with branched chain, ether linkage, glycerol, and phosphate group compared to Bacteria & Eukarya membrane lipid with unbranched chains]

Archaean cell wall contain distinct polysaccharides and proteins (lack cellulose and peptidoglycan).
Bacterial cell wall contain peptidoglycan (a polymer consisting of sugars and amino acids that provide structural support).
Eukaryotic cell wall in plants have cellulose and fungi have chitin.
Some archaea have pseudopeptidoglycan (differ from peptidoglycan in having sugars cross-linking patterns).

Metabolic differences
• Archaea have unique metabolic processes like methanogenesis (production of methane) not found in bacteria or Eukarya.
• Bacteria exhibit metabolic pathways, including photosynthesis, nitrogen fixation and fermentation.
• Eukarya have more complex metabolic processes including cellular respiration, photosynthesis (in plants and algae), and various forms of fermentation.

Biotechnology
The archaeans which live in high acidity and alkalinity are source of enzymes that can function under harsh conditions e.g. enzymes of DNA replication have been extracted from theses archaeans which are used in cloning of DNA (PCR-Polymerase Chain Reaction), these enzymes work best at high temperatures.
Sewage treatment
The methanogen archaeans carry out anaerobic digestion and produce biogas.
Biomining
The acidophilic archaea are used to extract metals such as gold, cobalt and copper from ores.

Major groups of Archaea
(i) Methanogens (produce methane as metabolic by-product)
(ii) Halobacteria (live in extremely saline environments)
(iii) Thermococci (found in hot environments)
(iv) Thaumarchaeota (involved in nitrogen cycle)

Yes, one of the major groups of Archaea i.e. methanogens are involved in production of intestinal gas leading to abdominal discomfort in humans. These are the part of normal flora of humans.

Appendages Bacteria possess pili and fimbriae, flagella-whip-like structures that enable locomotion pili-longer hair-like structures in some bacteria that help in conjugation i.e. exchange of genetic material with other bacteria. Fimbriae short hair-like protein appendages on bacterial surfaces, primarily involved in adhesion i.e. providing attachment to surfaces during colonization.

Plasmids are extrachromosomal, small, circular DNA molecules that can be transferred between bacteria, aiding in genetic diversity and adaptation, while chromosomal DNA is a single circular DNA located in nucleoid region involved in reproduction.

Extremophiles are the organisms including some bacteria that thrive or growth in extreme environmental conditions, unsuitable for most life forms.
Examples
(i) Thermophiles: adapted to high temperature.
(ii) Halophiles: adapted to high salinity
(iii) Acidophiles: can thrive in low pH (acidic PH).

Similarities
(i) Both archaea and bacteria possess prokaryotic cell, lack a true nucleus and membrane bound organelles.
(ii) Both possess a single, circular chromosome composed of DNA, located in the nucleoid region.
(iii) Both reproduce by asexual method especially binary fission and fragmentation.

Archaea occur in various shapes such as spherical, rod-shape, spiral, lobed or rectangular. Bacteria exhibit a variety of shapes. Such as cocci (spherical), bacilli (rod-shaped), spirilla (spiral shaped) and vibrios (comma-shaped).

Major groups of bacteria
(i) Proteobacteria e.g., Escherichia coli, Rhizobium, Helicobater pylori
(ii) Firmicutes e.g., Bacillus subtilis, Lactobacillus, Clostridium botulinum.
(iii) Actino bacteria e.g., Streptomyces, Mycobacterium tuberculosis
(iv) Cyanobacteria e.g., Anabeana, Spjulina
(v) Spirochaetes e.g., Treponema pallidum
(vi) Acido bacteria e.g., Acidobacterium
(vii) Aquificae e.g., Aquifex pyrophilus

Organized structures
Eukaryotic cells have true nucleus enclosed by a nuclear membrane, membrane bounded organelles e.g., mitochondria (makes cell energy efficient), chloroplasts (food factory) golgi apparatus, lysosomes, proteasomes, cytoskeleton i.e., complex network of microtubules, microfilaments and intermediate filaments that provides structural support. Enables cell movement and facilitates intracellular support.

Genetic Material
The DNA of a Eukaryial cells is organized into multiple linear chromosomes within the nucleus. Its DNA is associated with histone protein, which help in the organization and regulation of genes.

Reproduction
Most eukaryotes undergo sexual reproduction involving meiosis and fertilization leading to great genetic variety. Some eukaryotes can also reproduce asexually through mitosis, producing genetically identical offsprings.

Origin of eukaryotic cells
Eukaryotes are believed to have originated through endosymbiosis where certain prokaryotic cells engulfed by host cells (mitochondria & chloroplast) leading to a symbiotic relationship.

Taxonomic hierarchy refers to the system of classifying organisms into categories or groups, to understand the relationship between different forms of life. While each level which represents a rank in the biological classification system or taxonomic hierarchy is termed as taxan (pl-taxa)
Order of taxonomic hierarchy
All organisms → domain → kingdom → phylum → class → order → family → genus → species

Kingdom One of the highest taxonomic ranks, just below the domain, which groups together all forms of life that share fundamental characteristics.
e.g. Animalia, plantae, Fungi are different kingdoms.

Phylum The level of classification below kingdom, in which organisms share a basic body plan and significant structural features.
e.g., in Kingdom Animalia, the phylum chordata includes all animals with a notochord such as mammals, birds, reptiles, amphibians & fishes.

Class
Class divides organisms within a phylum based on more specific common traits e.g. within phylum Chordata, class mammalia includes all mammals or animals, which are characterized by having hairs and mammary glands.
While order categorizes organisms within a class based on additional shared characteristics and evolutionary history e.g. within class primates includes humans, monkeys and apes which are characterized by their large brains and opposable thumbs (a thumb that can be placed opposite the other fingers of hand for secure grip).

Species is the most specific basic level of classification representing a single type of organisms which can interbreed and produce fertile offsprings e.g. Homo sapiens, sapiens refers to modern humans. On the other hand genus more specific rank within a family, grouping species that are very closely related and often visually similar, e.g., within family Hominidae, the genus Homo includes humans and closest extinct relatives (Like Homo habilis, Homo erectus).

Domain Eukarya; Eukarya
Kingdom: Animalia; Plantae
Phylum: Chordata; Tracheophyta Angiosperms
Class: Mammalia; Monocots
Order: Primates; Asparagales
Family: Hominidae; Amaryllidaceae
Genus: Homo; Allium
Species: Homo Sapiens; Allium cepa

Domain Eukarya
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Passeriformes
Family: Passeridae
Genus: Passer
Species: Passer domesticus

Salient Features
Kingdom Protista includes eukaryotes which are unicellular, colonial, filamentous or simple multicellular organisms. (that do not have specialized multicellular sex organs).
Major Groups
1. Animal like protists (protozoans) e.g. paramecium, amoeba, plasmodium, trypanosoma.
2. Plant like protists (algae) e.g. euglena diatoms.
3. Fungi like protists myxomycota (slime molds) and oomycota (water molds).

Group Protozoa
• Includes animal like protists
• They are unicellular and heterotrophic.
• e.g., paramecium, amoeba, plasmodium and trypanosoma.
Group Algae
• Includes plant-like protists
• Cell walls of cellulose
• Have chlorophyll and are autotrophs
• e.g., euglena, diatoms, green algae, brown algae etc.
Group Myxomycota & Oomycota
• Include Fungi like protists
• They have hyphae like structure
• Are saprophytic
• e.g., slime molds (Physarum polycephalum), water molds (Phytophthora infestans)

Important Features
• Fungi are eukaryotic heterotrophic (absorptive) organisms.
• Unicellular or multicellular
• Cells are covered by cell wall made up of chitin (a polysaccharide)
• Get nutrients in a unique way, they do not ingest food like animals and protists, rather absorb food from surroundings.
• Examples include mushrooms, rusts, smuts, molds, yeasts etc.

Following are the major groups of fungi.
Zygomycota (Conjugating Fungi)
Includes fungi which lack septa in their hyphae (aseptate / non-septate / coenocytic hyphae) examples include Rhizopus (black bread molds) which grow on moist bread, fruits etc. Spirobulus (splitting fungus).
Ascomycota (Sac-fungi)
Largest group of fungi
Have septate hypha (hyphae having septa or cross walls)
Basidiomycota (Club-fungi)
Fungi with septate hyphae e.g. mushrooms, toadstools, puff balls, jelly fungi, bracket / shelf fungi. rusts and smut fungi.

Characteristics
Includes plants which are eukaryotic, multicellular organisms, having cell walls of cellulose.
• They are autotrophic (photosynthetic)
• Develop from embryos e.g. mosses, ferns, conifers, angiosperms.
• Plants are divided into two major groups
a) Bryophytes (non-vascular plants)
b) Tracheophytes (vascular plants)

Non-vascular plants Called bryophytes, Lack conducting tissues (xylem & phloem), e.g. liverworts, hornworts, mosses

Vascular plants Called tracheophytes, Posses conducting tissues, e.g. seedless plants (ferns) seed plants (conifers and flowering plants)

Water flow system
Sponges have two kinds of pores and a central cavity called spongocoel for filter feeding and water flow.
Pores
1. Ostia small incurrent pores through which water enters.
2. Osculum large excurrent pore, through which water leaves
Spongocoel the central cavity of sponges is called spongocoel.

Body structure
Body wall of sponges is made up of three layers.
• Outer layer-pinacoderm is made up of thin flat cells called pinaocytes.
• Middle layer-mesohyle is jelly-like layer, contains ambeboid cells.
• Inner layer-Choanoderm is third layer which lines the spongocoel, made up of choanocytes or collar cells.

Reproduction in sponges
• Sponges reproduce sexually as well as asexually. But most sponges reproduce asexually by budding or regeneration.
• Some sponges form resistant capsules called gemmules, when parent sponge dies, it releases its gemmules.
On arrival of favourable conditions, ameboid cells came out of the gemmules and form a new sponge.

Commercial sponge is prepared by drying, beating and washing a sponge until all cells are removed.
They are used in washing, bathing, used in surgical operations for fluids and blood absorption, also used for absorption of sound in building.
Examples: Leucosolenia Spongilla (Fresh water sponges)
Euplectella (Venus flower basket, marine sponges)

Characteristics
Cnidarians are radially symmetrical, diploblastic animals (with epidermis and gastro-dermis),
• Possess cnidocytes containing nematocysts for defense and prey capture.
• They have gastrovascular cavity with single opening serving as both mouth and anus.

Digestive Systems
Cnidarians have a sac-like type digestive system with one opening, Platyhelminthes also have sac-type digestive system, but have branched gastro vascular cavities allowing better nutrient distribution.

Body Plan
The adult body of a cnidarian contains two tissue layers, i.e.
(i) Epidermis (derived from ectoderm)
(ii) Gastrodermis (derived from endoderm)
(iii) Mesoglea: A jelly like mesoglea in between epidermis and gastrodermis mesoglea contains amoeboid cells that have originated either from ectoderm or endoderm.

Nematocysts
Cnidarians possess special cnidocytes, which contain a special organelle called nematocysts.
Nematocysts defend the body and enable cnidarians to capture prey without complete muscles complementing their simple digestive system.

1. Polyps
There are two body forms in cnidarians i.e. are cylindrical and are attached to a substrate at the aboral and they reproduce asexually by budding e.g. hydra.
2. Medusae
Medusae are umbrella like and are free swimming and use to reproduce sexually as they possess gonads e.g. jelly fish.

Removal of Waste
• Flatworms possess a network of tubular protonephridia (the excretory apparatus). These tubules have numerous branches. Which ends in a bulb-like e cell, called flame cell.
• The cilia of flame cells beat to suck the interstitial fluid (the fluid present between cells) and move into the tubules (excretory ducts).
• The tubules filter waste materials (nitrogenous waste) from the fluid and release them out of body wall through an external opening called nephridiopore.

Body Wall of Flat Worms
• Flatworms are triploblastic, acoelomate (having no body cavity), their tissues are derived from three embryonic layers, ectoderm (outer) endoderm (inner lines the gut) and mesoderm (middle forming a loose connective tissue called parenchyma, which fills space between the body wall and body organs.
• They possess bilateral symmetry with distinct left and right sides, as well as dorsal and ventral sides.

Following are few examples of flat worms.
i. Planaria
ii. Liver fluke
iii. Tapeworm

Anatomy
The parasitic round worms have excretory system of protonephridia and two excretory canals, which unite at the anterior end to form a single canal which opens outside through a nephridiopore on ventral surface.

Free living Caenorhabditis elegans, parasitic ascaris, hookworm, pinwarm whipworm.

Body Structure of Molluscs
Molluscs are triploblastic, coelomate protostomes (the coelomates in which blastopore form mouth, during embryonic development) their body is divided into three parts i.e.
a. Head,
b. Visceral mass (contains organs of digestion, excretion and reproduction),
c. Muscular foot (for locomotion).

Mantle Molluscs have an epithelial envelope around the visceral mass, called as mantle. The space between mantle and visceral mass is called mantle cavity. The outer surface of mantle secretes a calcareous shell in most of molluscs.
Radula: All molluscs (except bivalvia) have a rasping tongue like organ called radula. Which is used to scrap food (macrophagous type of feeding feeding).

Cardiovascular System
Except cephalopods, all the molluscs have open type of blood circulatory system where blood does not retain the vessel and directly bathes the cells in tissue space. Their heart consists up of single ventricle and two auricles.

Circulatory System
In open-type system, the blood does not retain the vessels, rather it directly bathes cells in tissue spaces (sinus), while the closed type system the blood flows in blood vessels and does not come in direct contact with tissues.
Cephalopod molluscs (octopus, cattle fish) are physically active, so the need more energy continuously that's why they need well maintained blood pressure, which is provided with closed type.
While other molluscs like snails, mussels, gastropods and bivalvia are not so physically active, that's why they need open type with low pressure.

There are three classes of molluscs.
1. Class gastropoda – slug, garden snail.
2. Class bivalvia – freshwater mussel, oyster marine water muscle.
3. Class cephalopoda – cuttlefish, octopus.

Ans. [See diagram showing anatomy of garden snail with labels for Intestine, Visceral mass, Mantle, Coelom, Stomach, Shell, Head, Eyes, Anus, Lower tantecle, Foot, Heart, Nerve cords, Gill, Mouth, Radula]

Segmentation
The body of annelids is divided transversely into a 'number of parts called segments. These segments are indicated externally by constrictions in the form of little rings (annelid = little ring) and internally the segments are separated by cross walls called septa.
Each segment is provided with its own circulatory, excretory and neural elements, this type of segmentation is called metameric segmentation.

Ans.
1. Nereis (marine water)
2. Leech (Fresh water)
3. Earthworm (damp soil)

Nervous System
The annelids possess cerebral ganglion or brain in the anterior segment. A double, longitudinal ventral nerve cord anus from brain and gives branches in each segment. (Ganglia are also present in each segment.
Receptors: The annelids being advanced animals possess tactile (touch) receptors, chemoreceptors (which detect chemical concentrations) balance receptors and photo (light) receptors.

Exoskeleton
Arthropods have exoskeleton or cuticle, secreted by the epidermis of body wall made up chitin (Polysaccharide) the young arthropods can't grow under this hard exoskeleton, so nature has provided them with a mechanism called moulting or ecdysis during which the exoskeleton is shed from time to time.
After shedding the exoskeleton, the animal grows at a faster rate and then re secretes new exoskeleton, which is larger than the previous one.

Tagmata
Tagmata are specialized, fused body regions (e.g. head, thorax, abdomen) in arthropods that is thought to be evolved from ancestral segmentation to enhance the functional efficiency, unlike the simple and uniform segments each having its own set of organs.

1. Respiratory System
Consists of air tubes called trachea, the main tracheal tube opens out through openings called spiracles, aquatic arthropods respire through gills.
2. Excretory System
Comprises of Malpighian tubules these are narrow tubules projected from alimentary canal, attached at the junction of midgut and hindgut. The nitrogenous waster are excreted in the form of solid aric acid crystals.
3. Nervous System
A well-developed CNS with three fused pairs of cerebral ganglia (brain) in head. There is double ventral nerve which has ventral ganglia in each segment smaller nerves arise from ventral ganglia in each segment.

Ans.
1. Class Curstacea
Crayfish, crab, lobsters, prawn, shrimp
2. Class Insecta
Wasp, grasshopper, butterfly, dragonfly, lady bird, mosquito, wasp.
3. Class Arachnida
Mite, spider, scorpion, tick
4. Class Myriapoda
Centipede, millipede

Symmetry
Echinoderms are triploblastic deuterosome coelomates, their larval forms exhibit bilateral symmetry but their adults show radial symmetry in which the body parts are arranged in five or multiples of five around the oral aboral axis.

Water-Vascular System
The water vascular system consists of tubes and spaces present in the coelom. A ring canal surrounds mouth, it opens outside through a sieve like plate, called madreporite which is connected to ring canal. From ring canal, there emerge lateral canals with each lateral canal ending into tube foot, which are the extensions of water vascular system. The tube feet extend and attach with substrate. When water is drawn back from the sucked tube feet. They contract and body is pulled.

Ans.
1. Cake urchin-biscuit shaped
2. Sea urchin-globular shaped
3. Sea cucumber-elongated body
4. Star fish (sea star)-star shaped with short arms
5. Brittle star-Star shaped with long arms.

Key Characteristics
Following four characteristics are unique to chordates present at some stage in development.
1. Notochord
2. Pharyngeal slits
3. Tubular nerve cord
4. Post anal tail

Notochord is a rod-like semi-rigid body of vacuolated cells (filled with proteinaceous material). Which extends throughout the length of body between gut and dorsal nerve cord during embryonic life.
Lower Chordates retain this notochord throughout life e.g. amphioxus. In higher chordates (vertebrates) it is partially or entirely replaced by vertebral column, during developmental stages.
Its primary purpose is to support and to stiffen the body that is to act as skeletal axis.

Pharyngeal slits are series of openings in the lateral walls of pharynx. All chordates develop paired gill. Slits in embryonic stages.
Transformations
• In some chordates (e.g. Amphioxus and fishes these develop into gill).
• In most amphibians these are functional for some period in their life history.
• In reptiles, birds and mammals these are modified for various purposes (e.g. formation of Eustachian tube in mammals).

Urochordata Sub-phylum of chordata which includes invertebrate chordates notochord and nerve cord are present only in their free swimming larvae. e.g. sea squirts, Molgula.

Cephalochordata Sub-phylum of chordata which includes invertebrate chordates in which notochord and nerve cord persists throughout the life. e.g., Amphioxus

Vertebrates
The animals (chordates) which have vertebral column and cranium, are called vertebrates.
Vertebrates are divided into seven classes which are placed into two groups.

Group Pisces includes 3 classes i.e. Cyclostomata, chondrichothyes and Osteichthyes, (don't have limbs).
Group Tetrapoda have four limbs, include 4 classes i.e. Amphibia, Reptilia, Aves and Mammalia.

Class Chondrichthyes Cartilaginous skeleton, Body covered by placoid (tooth like) scales, Pectoral & pelvic fins are paired. Two dorsal fins., Fertilization internal e.g. skate, ray, sharks

Class osteichthyes Bony skeleton, Body covered by dermal bony scales (ctenoid, ganoid, cycloid), Possess both median (dorsal, caudal and ventral) and paired (pelvic and pectoral) fins., Fertilization external e.g. lung fish, rohu, trout.

Amniotic Eggs
Lizard eggs will survive because they have amniotic eggs. Amniotic eggs make protective extra embryonic membranes i.e. amnion, allantois and chorion. These membranes protect the embryo from drying out. Nourish it and enable it to develop on land.
The amniotic eggs also contain a large amount of yolk the primary food supply for the embryo. Such eggs also contain abundant albumen which provides additional nutrients and water. The amniotic eggs are also covered with leathery calcareous shell which is partly permeable to gases but not to water.

Ans. [See diagram showing amniotic egg with labels for Chorion, Yolk sac, Allantois, Shell, Embryo, Amnion]

Ans. 1. Turtle
2. Cobra
3. Tuatara
4. Crocodile

Poikilotherms The animals which can't regulate their body temperature and can't maintain it constant, are called poikilotherms. They depend on external source of heat; so are called ectotherms. e.g. fishes, amphibians reptiles.

Homeotherms The animals which can maintain their core temperature are called homeotherms. They can obtain heat from cellular processes to maintain a nearly constant temperature, so are endotherms. e.g. birds and mammals.

Crop In many birds, there is a sac-like or pouch like structure (diverticulum) of esophagous which is called crop. It is a storage structure that allows birds to quickly ingest large quantities of food.
Gizzard is a region of stomach which has muscular walls to crush food (as the birds lack teeth).

Respiratory System
The birds have external nares, which open in pharynx through nasal passage ways. The pharynx leads to trachea and then to bronchi. The bronchi lead to a complex system of air sacs which connect to lungs. The lungs are made of small air tubes called parabroncii at the lower end of trachea, the organ of voice called syrinx is situated.

The bills (beaks) and tongues are of different shapes and sizes in order to adapt to specific diets feeding habits and food sources.
Emu, Kiwi, Pigeon, Sparrow, etc are some representative birds.

Flying birds are those which can fly e.g. pigeon, parrot, crow, eagle, robin etc but some birds have secondarily lost the power of flight and are called running birds. e.g. ostrich, kiwi, rhea, crossway, emu, penguins etc

Characteristics of Mammals
Mammals are called mammals, because their females possess mammary gland, so they are nourished by milk from the mammay glands of mother and have hair on their body.
Skin
Mammals have skin glands developed from epidermis. Like, sebaceous (oil) glands, sudoriferous (sweat) glands.
Teeth
Most of them have two sets of teeth during their lives i.e. milk (deciduous teeth and permanent teeth enter presence of external ear or pinna.
Middle ear bones i.e. malleus, incus and stapes.
Possess diaphragm that separates coelom into thoracic and abdominal cavities.

Oviparous are those animals which lay eggs e.g. fishes, amphibians, reptiles and birds.
VivIparous are the animals which give birth to young ones.
Ovoviviparous are some rare animals which whole development of their embryo proceeds and are retained in mother's body. e.g. Duckbill platypus and echidna (spiny ant-eater).

Pouch in Mammals
Some mammals have a pouch or marsupium on the abdomen of their females because these mammals give birth to immature young ones which need to complete the remaining development in mother's pouch e.g. kangaroo opossum & Tasmanian wolf.

Placental mammals are considered most advanced because, during developmental stages a structure called placenta, is formed between mother's uterus and foetus body. The foetus is nourished and wastes from foetus are removed through placenta, e.g. dolphin, elephant, rat, monkey, bat, humans etc

Prions and viroids are also acellular entities. They are also not considered living organisms. Prions are composed of protein only and viroids are composed of circular RNA only. Both these particles cause infectious diseases in certain plants.
Examples: Potato Spindle tuber disease, chrysanthemum stunt disease etc.

Viruses are Acellular
Viruses are not considered organisms because they are acellular i.e. not made of cells. They lack any of the characteristics of the three domains of life and are not classified in any domain and kingdom.
A virus consists of nucleic acid (DNA or RNA) surrounded by a protein coat. They cannot run any metabolism and depend upon the host cell (including plants, animals, and bacteria) to replicate and synthesize their proteins.

Classification of Viruses
Viruses are classified based on several characteristics, including their genetic material, replication strategy, morphology, and the hosts they infect. The classification of viruses follows guidelines established by the International Committee on Taxonomy of Viruses (ICTV).

Ans.
1. Animal Viruses: Infect animals, including humans. Examples: Influenza virus, Rabies virus.
2. Plant Viruses: Infect plants. Examples: Tobacco mosaic virus, Potato virus X
3. Bacteriophages: Infect bacteria. Examples: T4 phage, Lambda phage.
4. Archaea Viruses: Infect archaea. Examples: Sulfolobus spindle-shaped virus.

Ans. 1. Helical Viruses These have a capsid with a helical structure surrounding the nucleic acid.
Examples: Tobacco mosaic virus, Rabies virus.
2. Icosahedral Viruses: These have a capsid with a symmetrical icosahedral shape.
Examples: Adenoviruses, Herpesviruses.
3. Complex Viruses: These have a complex structure, often with a combination of icosahedral and helical features, and sometimes additional structures like tails.
Examples: Bacteriophages (viruses that infect bacteria).
4. Enveloped Viruses: These have an outer lipid envelope derived from the host cell membrane, surrounding their capsid.
Examples: Influenza virus, HIV
5. Non-enveloped (Naked) Viruses: These lack an outer lipid envelope and consist only of a capsid enclosing the nucleic acid.
Examples: Polio virus, Adenovirus.

Ans. 1. DNA Viruses Viruses with DNA as their genetic material. This DNA can be single-stranded (ssDNA) or double-stranded (dsDNA). Examples include:
• dsDNA viruses: Adenoviruses (cause respiratory infections), Herpesviruses (cause herpes, chickenpox).
• ssDNA viruses: Parvoviruses (cause gastroenteritis).
2. RNA Viruses: Viruses with RNA as their genetic material. This RNA can be single-stranded (ssRNA) or double-stranded (dsRNA). Examples include:
• ssRNA viruses: Coronaviruses (cause COVID-19), Influenza viruses (cause flu).
• dsRNA viruses: Rotaviruses (cause gastroenteritis).

Ans. 1. Positive-Sense RNA Viruses
The RNA genome is directly translated into proteins by the host cell's ribosomes. Examples include Poliovirus, Hepatitis C virus.
2. Negative-Sense RNA Viruses
The RNA genome is transcribed into mRNA by a viral RNA polymerase before translation. Examples include Rabies virus, Ebola virus.
3. Reverse Transcribing Viruses
These viruses replicate through a DNA intermediate using the enzyme reverse transcriptase. They can have RNA or DNA genomes.
Examples include:
• RNA genome: Retroviruses like HIV (cause AIDS).
• DNA genome: Hepadnaviruses like Hepatitis B virus.

Ecosystem
An ecosystem is a dynamic and interactive system composed of living organisms and their physical environment. It includes all the biotic factors as well as the abiotic factors.
Niche
A niche refers to the role or function of an organism or species within an ecosystem. It includes its habitat, its interactions with other organisms (predation, competition, and symbiosis), and its role in energy flow within the ecosystem.

Biodiversity, a term derived from "biological diversity," refers to the variety of life forms present in different ecosystems, encompassing the diversity of species, genes, and ecosystems.
It represents the richness and variability of living organisms and their interactions with each other and their environments it is assessed at three levels.
1. Species level
2. Genetic level
3. Ecosystem level

Species Level At the species level, biodiversity is assessed by identifying and counting the different species present within a given area. Species diversity includes not the number of species but also their relative abundance and distribution.
Genetic Level: At the genetic level, biodiversity refers to the variety of genetic information contained within all individual organisms of a species. This genetic diversity is crucial for the adaptability and survival of species, enabling them to cope with environmental changes and challenges.

Random sampling is a fundamental technique in ecological studies for assessing biodiversity within a specific area. This method is crucial for several reasons.
• It minimizes bias ensuring the equivalent chance of sampling from every part
• It provides reliable estimates allowing collection of data for statistical analysis
• This method facilitates comparisons between different areas.
• Enhances representativeness by covering different parts of study area.
• It supports conservation efforts for monitoring changes in biodiversity over time.

Distribution of Biodiversity
The distribution of biodiversity can be assessed by using the following methodology.
1. Quadrat sampling
2. Transect sampling
3. Aerial surveys

1. Quadrat Sampling
It involves dividing the study area into a grid and sampling within randomly selected squares (quadrats). This method is particularly useful for studying plant populations or sessile organisms. For example, in a forest, a researcher might lay out quadrats of a fixed size and record the presence or absence of each plant species within these quadrats.
2. Transect Sampling
It involves laying out a line or strip (transect) across the study area and recording species at regular intervals along this line.
• This method is effective for studying the distribution of species across different conditions. For example, in a coastal zone, a transect can be laid from the high tide line to the low tide line, to record the types and abundance of intertidal organisms.

Ans.
1. Point counts
2. Mark recapture
3. Quadrat Counts
4. Capture recapture methods
5. Remote sensing

Species
The term "species" is a fundamental concept in biology. A species is generally defined as a group of individuals that can interbreed and produce fertile offspring under natural conditions. Members of the same species share common characteristics and genetic makeup, which distinguishes them from individuals of other species.
Speciation
Speciation is the evolutionary process by which new species arise from a common ancestor. It involves the accumulation of genetic changes that lead to reproductive isolation between populations. There are several mechanisms of speciation.

Allopatric speciation
• It occurs when a population is geographically separated into two or more isolated groups.
• Over time, the accumulated differences can become significant enough to prevent interbreeding, even if the geographical barrier is removed.
• An example is the speciation observed in Darwin's finches on the Galápagos Islands, where different populations adapted to diverse environments.

Peripatric speciation
• It involves a small, isolated population at the edge of a larger population. The small population undergoes rapid evolutionary changes, leading to divergence from the original population.
• An example can be seen in island species that evolve from a small founding population.

Parapatric speciation
• This occurs when populations are adjacent to each other but occupy different environments along a gradient.
• Gene flow between the populations is limited, and they evolve adaptations to their specific environments. Over time, this can lead to reproductive isolation.
• An example is the grass species "Anthoxanthum odoratum", which exhibits different adaptations to varying soil conditions across a gradient, leading to reproductive isolation in different soil types.

Sympatric speciation
• In this form, new species arise within the same geographical area without physical barriers.
• Sympatric speciation often occurs through mechanisms such as polyploidy (where an organism has multiple sets of chromosomes) or niche differentiation (where different subpopulations exploit different resources).
• For instance, certain plants can undergo polyploidy, leading to immediate reproductive isolation and the formation of new species.