12. Patterns in Life: Diversity and Classification | Class 9 Science | PDF and Web notes

12

PATTERNS IN LIFE: DIVERSITY AND CLASSIFICATION

• The immense variety of living organisms on the Earth is called biodiversity.
• Biodiversity is essential for life on Earth because it maintains ecological stability and balance. E.g.,
  • Algae in the oceans release most of the oxygen.
  • Fungi and bacteria decompose dead matter and convert waste into manure.
  • Birds, bees and bats pollinate flowers.
  • Plants capture sunlight to prepare food.
• Farmers conserved crop varieties with pest resistance, drought tolerance and ability to grow in nutrient-poor soils. It reduces crop failure and improves food security.
• To study diversity systematically, organisms are classified based on their shared characteristics and evolutionary relationships.
• Classification helps understand relationships among organisms, their functions, and uses in ecosystem management, conservation, and sustainable farming.

INDIA AS A BIODIVERSITY HOTSPOT

• India has diverse natural landscapes, including northern mountains, western deserts, North-Eastern rainforests, southern plateaus, and coastlines along the Arabian Sea and Bay of Bengal.
• They differ in soil type, temperature, and rainfall, creating diverse habitats that support variety of species.
• Species found naturally only in a particular region are called endemic species. Examples in India include Nilgiri tahr, Lion-tailed macaque, Nepenthes khasiana (a pitcher plant), and Neelakurinji.
• Biodiversity hotspots: These are regions with many endemic species and high habitat loss, making them important for conservation. E.g., Western Ghats, Indo-Burma (including North East India), the Himalayas, and Sundaland (including the Nicobar Islands).
• These regions maintain ecosystems and food webs.

INDIA AS A BIODIVERSITY HOTSPOT

• India has diverse natural landscapes, including northern mountains, western deserts, North-Eastern rainforests, southern plateaus, and coastlines along the Arabian Sea and Bay of Bengal.
• They differ in soil type, temperature, and rainfall, creating diverse habitats that support variety of species.
• Species found naturally only in a particular region are called endemic species. Examples in India include Nilgiri tahr, Lion-tailed macaque, Nepenthes khasiana (a pitcher plant), and Neelakurinji.
• Biodiversity hotspots: These are regions with many endemic species and high habitat loss, making them important for conservation. E.g., Western Ghats, Indo-Burma (including North East India), the Himalayas, and Sundaland (including the Nicobar Islands).
• These regions maintain ecosystems and food webs.

HOW HAS THE BIODIVERSITY EVOLVED?

• The biodiversity has changed over time as small variations. It helped organisms survive, adapt and reproduce under changing conditions. Gradually new life forms evolved.
• Thus, present-day biodiversity is the result of continuous changes shaped by interactions between organisms and their environment.

India's Scientific Contributions

• Ancient Indian traditions like Sangam Tinai classification and sacred grove protection showed an advanced understanding of landscapes and biota.
• These customs helped conserve diverse habitats and align with modern ecological principles.

HOW TO CLASSIFY ORGANISMS?

Classification provides a systematic framework for studying biological diversity.

Activity: Let us compare and classify

Some animals found in forest and their features

Organism	Where do you see it?	When does it appear active?	Any visible feature(s)
Owl	Tree	Night	Feathers, large eyes
Eagle	Flying high in air	Day	Large wings, sharp beak
Tiger	Forest floor	Day / Night transitional	Stripes, paws, fur
Leopard	Tree / Forest floor	Day	Rosette spots on coat
Deer	Forest floor	Day	Antlers/horns, slender legs
Bat	Flying near the ground/air	Night	Leathery wings
Frog	Water / Near water	Day and Night	Moist, smooth skin
Porcupine	Forest floor	Night	Sharp quills/spines
Crocodile	Water	Day and Night	Scaly, armoured skin

Grouping the organisms

The grouping criterion	Which organisms fit in this group?	What feature or pattern helped you decide?
Carnivore	Eagle, tiger, leopard	Eating habits
Herbivore	Deer, rabbit	Eating habits
Tree-dwelling	Langur monkey, owl, slow loris, leopard	Habitat
Terrestrial	Tiger, deer, rabbit, porcupine	Habitat
Aquatic/Semi-aquatic	Frog, crocodile	Habitat
Flying	Eagle, bat, dragonfly	Locomotion
Walking/Running	Tiger, leopard, deer, bear, rabbit	Locomotion

• The same organism may belong to different groups based on the criteria used. Therefore, scientists use classification, a systematic method of organising biodiversity based on selected features.

Some criteria to classify living organisms

• Organisms are classified by first observing broad, visible features and then detailed features.
• 1. External features: Visible characteristics, such as shape, size and body organisation.
• 2. Mode of nutrition: Autotrophic or heterotrophic.
• 3. Internal structures: Skeletal patterns, presence or absence of organs and various tissues.
• 4. Cell structure: Unicellular or multicellular, eukaryote or prokaryote, presence or absence of cell wall.
• 5. Ecological role: Producer, consumer or decomposer.
• 6. Reproduction: Asexual or sexual.
• 7. Genetic similarity: Similarities in inherited features, using DNA.

Pause and Ponder

• 1. If many organisms share common features, could they also share a common ancestry?
  Answer: Yes. Organisms with common features share a common ancestry because these traits were inherited from a shared ancestor.

Similarities and differences in features help classify organisms. Similar features indicate common ancestry.

THE NEED FOR CLASSIFICATION

Just as arranging books in a library makes them easier to find, systematic classification helps us study and understand Earth’s millions of organisms more easily.

Activity: A case study

• Pakke Tiger Reserve (Arunachal Pradesh) supports nearly 300 bird species (India has 1,300 bird species), including four hornbill species: the Rufous-necked Hornbill, Oriental Pied Hornbill, Great Hornbill, and Wreathed Hornbill.
• These hornbills depend on large old trees with nesting cavities and specific fruits, so their distribution varies with tree size and fruit availability.

Pause and Ponder

• How are species distributed within a forest? Which plants and animals are closely linked?
  Answer: Species are distributed vertically across different layers of the forest (e.g., canopy, understory, and forest floor) based on their adaptations. Plants and animals are closely linked through ecological relationships. E.g., large canopy trees are directly linked to hornbills by providing with fruits and nesting cavities.
• How does classifying the four hornbill species help us understand biodiversity?
  Answer: This helps us understand biodiversity by revealing the distinct variations, unique adaptations, and specialized ecological roles that exist among closely related organisms within the same habitat.
• How can scientists keep track of so many species?
  Answer: Scientists track numerous species by biological classification, which organizes organisms into hierarchical groups based on their shared characteristics.
• The four hornbills look similar in some ways. What features can help scientists distinguish them from one another?
  Answer: Scientists can distinguish them by observing variations in external features (body size, plumage colors, and size or shape of beaks etc.) along with their habitat distribution and diet preferences.
• What would happen if the large, old trees disappeared from the forest?
  Answer: The hornbills would lose their nesting cavities and food sources, leading to their decline or extinction.

Biological classification is the scientific grouping of organisms based on similarities and differences in external features, internal structure, and cellular organisation. This helps to organise information and understand relationships among organisms and study life in a systematic manner.

Importance of Biological Classification:

1. To study organisms more organised and systematic.
2. To understand the similarities and differences among organisms.
3. To understand how different organisms are related to one another and how they interact.
4. To identify and name the newly discovered organisms.
5. It supports biodiversity conservation by identifying the organisms under the threat of extinction.
6. It provides a common system for scientists worldwide to study and discuss organisms.

BIOLOGICAL CLASSIFICATION SYSTEMS OVER TIME

• Aristotle, the 4th century BCE, grouped animals based on their habitat—land, water and air. He also grouped them based on their external appearances.
  Limitation: It relied mainly on easily observable external characteristics.
• Carolus Linnaeus introduced Two Kingdom classification system (1758) - Plantae and Animalia.
  • Plantae— do not move from one place to another. Synthesise their own food.
  • Animalia— move from one place to another. Depends on other organisms for food.
  Limitation: Confusion regarding the position of organisms like Amoeba, Paramecium and bacteria. Amoeba and Paramecium can move but are unicellular and heterotrophic. However, plants and animals are multicellular organisms.
• Ernst Haeckel proposed Three Kingdom system (1866) by placing unicellular microscopic organisms under kingdom Protista.
  Limitation: Bacteria, Amoeba etc. are unicellular but very different. E.g., Amoeba has a true nucleus but bacteria do not.
• Herbert F. Copeland proposed Four Kingdom system (1938) by placing bacteria in kingdom Monera.
• Fungi like mushrooms, do not move like plants but have a heterotrophic nutrition. They obtain nutrients by absorption from dead and decaying matter (some are symbiotic and parasitic). Therefore, Robert H. Whittaker (1969) proposed Five Kingdom classification by placing fungi in kingdom Fungi.

Scientist / Year	Classification System
Aristotle 4th century BCE	Artificial System Grouped animals by habitat — land, water and air
Carolus Linnaeus 1758	Two Kingdom Plantae, Animalia
Ernst Haeckel 1866	Three Kingdom Protista, Plantae, Animalia
Herbert F. Copeland 1938	Four Kingdom Monera, Protista, Plantae, Animalia
Robert H. Whittaker 1969	Five Kingdom Monera, Protista, Fungi, Plantae, Animalia

FIVE KINGDOM CLASSIFICATION

• In this, organisms are grouped based on some common features. Some criteria are given below:
  • Cell type — prokaryote or eukaryote
  • Cell structure — presence or absence of a cell wall
  • Level of organisation — unicellular or multicellular
  • Mode of nutrition — autotrophic or heterotrophic

Five kingdom classification - Concept map

Kingdom Monera - Unicellular prokaryotes

• Monera includes single-celled prokaryotes such as Bacteria and cyanobacteria.
• Bacteria occur everywhere, including soil, water, air, extreme environments, hot springs, and in human body.
• Some bacteria live in the gut of ruminants and produce biogas from the dung.
• Some bacteria are pathogens (cause diseases).
• Many are useful like Lactobacillus and Rhizobium.
• Cyanobacteria are autotrophs and decomposers.
• In addition to nutrient cycling, some bacteria also break down pollutants like oil, pesticides, sewage, and so on.

Bridging Science and Society

• Ram Bux Singh (Father of Modern Biogas) established India’s first scientifically designed biogas plant in 1957 at Ramnagar, Sitapur, Uttar Pradesh.
• He developed low-cost biogas plants for rural areas and promoted renewable energy, waste management, and sustainable development.

Threads of Curiosity

• Cyanobacteria (blue-green algae) were among the first organisms to produce oxygen through photosynthesis, leading to oxygen accumulation in Earth’s atmosphere about 2.5 billion years ago.
• Their fossils occur in structures called stromatolites found in Rajasthan and Madhya Pradesh.

Kingdom Protista

• It includes microscopic unicellular eukaryotes without cell wall or with cell wall made up of cellulose.
• They live in water or moist places.
• Some are autotrophic and others are heterotrophic.
• E.g., Amoeba, Paramecium, Euglena.

Activity: Making hay infusion

• Collect grass, straw, or fodder and place it in a bottle one-fourth filled with plant material.
• Add stagnant or pond water, cover with muslin cloth, and keep undisturbed for a week.
• Take a drop of water from the bottle, put on a slide and observe under a microscope.
• Some moving organisms such as Amoeba, Paramecium, Euglena etc. can be seen.

Amoeba

Paramecium

Euglena

Importance of protists:

• They are important link in aquatic food chains.
• Some produce oxygen.
• Serve as food for small animals.
• Some are decomposers and help in nutrient cycling.

Pause and Ponder

• How can a single-celled organism carry out all its life processes when billions of cells are required to perform similar functions in multicellular organisms like us?
  Answer: Unicellular organisms perform all life processes within one cell using organelles, and its small size allows easy exchange of materials by diffusion and osmosis. Multicellular organisms need many cells because their larger size requires specialised tissues.

Kingdom Fungi

• Fungi are heterotrophic and mostly multicellular eukaryotes with cell walls made of chitin.
• They absorb nutrients from dead or decaying matter through fine filaments (form a network called mycelium).
• Fungi are saprophytic decomposers that break down complex organic matter into simpler minerals, recycle nutrients, and maintain soil fertility and ecological balance. So they have important ecological role.
• Some establish a mutualistic (symbiotic) relationship with other organisms. Others live as parasites, and cause diseases in plants and animals.
• They reproduce sexually and asexually, by forming spores, and grow best in warm and moist conditions.
• Yeast and bread mould (Aspergillus) are common fungi.
• Yeast is unicellular. It is grouped under fungi because its cell wall is made up of chitin.
• Mushrooms are macroscopic fungi that reproduce by spores.
• Some fungi like Aspergillus and Penicillium are used to make enzymes and antibiotics.

Bridging Science and Society

• Wild edible mushrooms are nutritious and medicinal forest resources used by many communities, including tribal groups in India, who identify edible and poisonous varieties through traditional knowledge.
• Some mushrooms are used as food and medicine, and mushroom cultivation is becoming a promising livelihood due to its low investment, small space requirement, and short growth cycle (30–45 days).

Bridging Science and Society

• Lichens are seen as white-green patches on tree trunks, walls, and stones, and are considered indicators of pollution-free environments because they change colour with air pollutants. Based on their colour, researchers can find out the concentration of pollutants in the air.
• They act as natural bioindicators of air quality.
• Some lichens, commonly called patthar ke phool are used as a spice. Some are used as medicines, and for making dyes to give maroon, violet, or burgundy colour to woollen and silk fabrics.
• Lichens are symbiotic associations between an alga (prepares food by photosynthesis) and a fungus (provides protection).
• Since some lichens are poisonous, proper identification and classification are important for safe use.

Kingdom Plantae

• Plants are multicellular, autotrophic organisms that perform photosynthesis.
• Their rigid cell wall primarily made up of cellulose. It provides support and protection.

Classes of Kingdom Plantae with their advantages and challenges

Plant groups	Salient features & examples	Advantages for survival	Exceptions/ Challenges
Thallophyta (Algae) (thallos= undifferentiated body, phyton= plant)	Simplest plants found in water or moist environment. Well-adapted to aquatic habitats. Body is like a thallus, a simple body that allows easy absorption of water and nutrients, and exchange of gases from the surroundings. E.g., Spirogyra	Primitive plant body facilitates survival and its dispersal in water.	They cannot live on land.
Bryophyta (bryon= moss, phyton= plant)	Represent an important shift from water to land. Began to colonise land but depend on moisture. Body is more differentiated than thallophytes. They have rhizoids (root-like structures), stem-like and leaf-like simple structures. Lack vascular tissues for water and food transport. Need water for reproduction, as male reproductive cells must swim to reach female cells. So, they are called 'amphibians' of the plant kingdom. E.g., Mosses and liverworts (Marchantia).	They are plant amphibians. Adapted to live on moist and shady places.	Always need moisture.
Pteridophyta (pteris from pteron= feather, phyton= plant)	True roots, stems and leaves. Have vascular tissues (xylem and phloem) that transport water and food throughout the plant. They depend on water for reproduction. They do not produce seeds. E.g., Ferns.	Adapted to live on land. Transport food and water to all plant parts.	No reproduction without water.
Gymnosperm (gymnos= naked, spermos= seed)	Well-adapted to cold and dry land regions. Needle-like or scale-like leaves reduce water loss. Water is not essential for fertilisation. They produce seeds, which protect the developing embryo and contain stored food. Seeds are exposed on cones (not enclosed in fruits). E.g., Pines and cycads.	Leaves adapted for dry conditions. No need of water for reproduction. Seeds for continuity of life.	Seeds are not covered in the form of fruits.
Angiosperm (flowering plants) (angeion= vessel, spermos= seeds)	Plants with the most complex body organisation. Well-developed roots, stems and leaves. Sexual reproduction through flowers. It attracts pollinators for efficient reproduction. Seeds are enclosed within fruits. Fruits help seed dispersal by insects, birds, animals, wind, or water. So, they are most diverse plant group. They are grouped as monocots or dicots based on leaf shape, venation, and seed structure.	Produce flowers, fruits and seeds. Well-developed system for reproduction. Seeds for continuity of life. Seeds are covered.	Depends on pollination agents. Complex processes through well-developed tissue system.

• Early plants depended on water for support and reproduction. Later, plants evolved transport tissues, seeds & flowers.
• Plant diversity reflects different adaptations for growth, transport, reproduction, and survival in various environments.

Examples:

Thallophyte	Bryophyte	Pteridophyte	Gymnosperm
		Cross section of a fern stem

Activity: Let us compare

• Compare the cross section of the stem of a fern with a cross section of sunflower stem.
• What difference do you observe in the vascular tissue of the fern stem and of the stem of higher plants?

Answer

• Fern stem: Vascular tissues are arranged as stele.
• Sunflower stem: Vascular bundles are arranged in a ring around the pith.
• Fern stems: Vascular tissue is simple and lacks a well-developed cambium and secondary growth.
• Higher plants: Vascular tissue is more advanced, with xylem and phloem arranged in vascular bundles, often having cambium that allows secondary growth.

Pause and Ponder

• Which plant features reduce their dependence on water but still require moist conditions?
  Answer: Rhizoids and a simple cuticle reduce water loss, but these plants still need water for male gametes to swim during fertilisation.
• Why do taller plants need specialised transport tissues?
  Answer: Taller plants need xylem & phloem because diffusion alone cannot efficiently transport water, minerals and food over long distances against gravity.
• How do seeds and fruits affect, where and how plants can survive?
  Answer: Seeds protect and nourish embryos during harsh conditions, while fruits help seed dispersal to new habitats by wind, water, or animals.

Bridging Science and Society

The book Hortus Malabaricus was compiled in the 17th century by Hendrik van Rheede with the help of Itty Achudan. It documented Indian plants and their medicinal uses, combining traditional knowledge with science.

Kingdom Animalia

• Animals are multicellular & heterotrophic eukaryotes.
• Most animals exhibit locomotion, rapid response to stimuli and coordinated behaviour.
• A major criterion for classifying animals is the presence or absence of a notochord (a flexible rod-shaped structure). Based on this, animals are 2 groups—non-Chordata (Invertebrata) and Chordata.
• In some chordates, notochord acts as a precursor for the development of the vertebral column.
• Chordata is classified as Protochordata & Vertebrata.

Invertebrates

• They lack a notochord and show body organisation ranging from simple forms to complex organ systems.
• Their study reveals the gradual evolution of movement, feeding habits, and control and coordination in animals.

Porifera (pore-bearers/ Sponges) - Multicellularity without tissues

• They are aquatic and remain fixed in one place.
• They are multicellular with simplest body plans.
• They lack organisation of tissues and organs.
• Body has numerous pores. Water flows through it carrying food particles and oxygen to individual cells and removing the waste away.
• Sponges cannot survive on land because they depend on water currents for food and oxygen.

Cnidaria - True tissues and active feeding

• Cnidarians show tissue-level organisation which allows specialised cells to perform specific functions. E.g. tentacles are used to capture prey.
• A single opening for food intake and waste removal.
• Limitation: A single opening prevents continuous feeding and makes digestion less efficient because all digestive processes occur in one cavity.
• E.g., Hydra, jellyfish and corals.

LS of hydra showing tissue level organisation

Jelly fish

Platyhelminthes (flatworms) - Bilateral symmetry and directional movement

• Bilateral symmetry (body can be divided into two halves along one plane) with distinct head-tail and front-back regions. It enables better movement and is the beginning of directional activity.
• Flattened body for efficient diffusion of gases without specialised respiratory organs.
• A single opening for food intake and waste elimination.
• Many are parasites. Hooks and suckers help them to attach firmly to the host tissues for obtaining nutrients.

Nematoda (roundworms) - Efficient body design with two openings

• Roundworms have elongated, cylindrical bodies which enables efficient movement through soil, water, or host tissues. It also increases survival in diverse environments, despite simple internal organisation.
• Body has two openings (mouth and anus).
• The organ system level of body organisation is distinct in male and female worms.

Annelida (segmented worms) - segmentation and body cavities

• Cylindrical body divided into segments.
• Segmentation gives flexibility and precise movements.
• Organ system level of organisation.
• Muscles help in locomotion.
• Nerve cord helps in control and coordination.
• A body cavity is present.
• E.g., earthworm.

Arthropoda - Jointed appendages and an external skeleton

• Arthropods (arthro= joint, poda= appendages) have segmented body with different segments specialised for different functions.
• A defining feature is a hard external skeleton (rigid external covering). It provides protection, reduces water loss and supports muscles, so arthropods can survive in dry and exposed environments.
• E.g., insects, crabs & spiders.

Pause and Ponder

6. An earthworm (Annelida) and a beetle (Arthropoda), both have segmented bodies but the beetle has a hard external skeleton. How does the beetle’s external skeleton help it survive?

Answer: The beetle’s exoskeleton protects against predators, prevents water loss, and provides support for muscle attachment, movement, and flight.

Mollusca - Organ system level organisation with soft bodies

• Body is segmented with a distinct head, a muscular foot and a hump.
• Many molluscs have a shell that protects the soft body.
• This group shows how a basic body plan adapts differently to environmental demands.
• E.g., snails, squids and octopuses.

Echinodermata - Internal support without notochord

• Echinoderms (echinos= spiny, derma= skin) have a hard internal skeleton made of calcium carbonate.
• Internal skeleton provides protection and controlled movement.
• Body organisation is like that of complex animals, showing a shift towards internal skeletal support.
• E.g., starfish and sea urchins.

Looking across invertebrates

• From sponges to echinoderms, animal body structures show increasing complexity, with new features improving feeding, movement, protection, and survival in diverse environments.

Characteristics of various Invertebrate Phyla

Feature	Habitat	Level of organisation	Skeleton
Porifera	Water (Marine)	Cellular	X
Cnidaria	Water (Fresh & marine)	Tissue	X
Platyhelminthes	Water/inside host	Organ	X
Nematoda	Soil/water/inside host	Organ system (digestive system)	X
Annelida	Moist soil/water	Organ system	X
Arthropoda	Land/water	Organ system	Exoskeleton
Mollusca	Water/moist land	Organ system	Exoskeleton
Echinodermata	Marine water	Organ system	Endoskeleton

Protochordates — The appearance of the notochord

• Protochordates (like Amphioxus) possess a notochord at least once during their life. This provides internal support without restricting movement and represents a crucial change in body organisation.
• Protochordates are a primitive type of chordates which help us understand how animals with a notochord may have arisen from simpler forms.

Vertebrates — Animals with a backbone

• They have a vertebral column (backbone), an internal skeleton that supports body and protects vital organs.
• 5 groups: fish, amphibians, reptiles, birds & mammals.

Bridging Science and Society

Forests create physical, biological and chemical barriers to protect against challenges and disasters. E.g.

• Mangroves helped reduce damage during the super cyclone in Odisha (1999).
• Rich biodiversity can reduce tick-borne disease risk. E.g., in the Western Ghats, forest diversity helps limit the spread of Monkey Fever (Kyasanur Forest Disease, KFD) by providing hosts in which the virus cannot replicate.
• Microorganisms in forest soils and plant roots absorb, transform, or break down pollutants. This improves water quality and protects ecosystems. Mangrove soils trap sediments and heavy metals, preventing pollution.

ADAPTATIONS AS OUTCOMES OF STRUCTURAL CHANGE

• Animal diversity is the outcome of long-term changes in body structure over time. E.g.
  • Fins & gills allow fish to move and breathe in water.
  • Feathers and hollow bones enable flight in birds.
  • Fat storage in camels and thick fur in polar bears aid survival in extreme conditions.
  • In mammals, mammary glands improve the survival of young ones.
• Such features are interconnected and reflect how vertebrates adapt to survival in different environments.

The hierarchical nature of classification

• Classification progresses from broad groups to smaller, more specific ones.
• At each lower level, organisms share more common features. Every group is a part of the group above it.

Kingdom → Phylum → Class → Order → Family → Genus → Species

• Like an address, classification helps identify, compare, and understand relationships among organisms.

Kingdom	Animalia
Phylum	Chordata
Sub-phylum	Vertebrata
Class	Mammalia
Order	Carnivora
Family	Felidae
Genus	Panthera
Species	P. tigris

Kingdom	Plantae
Phylum	Magnoliophyta
Class	Magnoliopsida
Order	Fabales
Family	Fabaceae
Genus	Pisum
Species	P. sativum

SCIENTIFIC NAMING - THE BINOMIAL SYSTEM

• Different languages use different names for the same organism. It causes confusion.
• To avoid this, Carolus Linnaeus proposed a universal system of naming organisms called binomial nomenclature.
• According to this, every organism has a scientific name with two parts, written in Latin or a Latinised form. E.g.

S. No.	Common name	Scientific Name
1.	Tiger	Panthera tigris
2.	Mango	Mangifera indica

• First word is the genus name. E.g. Panthera, Mangifera.
• Second word is the species name. E.g. tigris, indica.
• A genus groups closely related species that share common features. E.g. Panthera tigris and Panthera leo under the genus Panthera (the roaring cats), have similar skull structure.
• The species indicates a group of organisms that consists of similar individuals capable of interbreeding and producing offsprings.

Rules for writing the scientific names:

• The name (Latin or Latinised form) has two parts—genus and species.
• Genus name begins with capital letter and comes first. It is followed by species name written in small letters.
• The scientific name is written in italics when printed, or underlined when handwritten.

Ready to Go Beyond

• Advances in microscopy and genetic research, especially DNA studies, led to modifications of the five-kingdom classification.
• Organisms with similar DNA are considered to have a common ancestry. Based on the genetic data, Carl Woese (1977) proposed the three-domain system:
  • Bacteria
  • Archaea
  • Eukarya

Threads of Curiosity

• Science evolves with new discoveries and technologies.
• New tools, such as microscopes and staining techniques, led to the discovery of microorganisms and changes in biological classification. It shows that science is a continuous process of reasoning and revision.

Meet a Scientist

• Birbal Sahni studied fossil plants and founded the Birbal Sahni Institute of Palaeosciences in Lucknow.
• His work linked present-day plants with their ancestors and showed the long evolutionary history of life on Earth.

Pause and Ponder

• Does the term ‘biodiversity’ relate only to the variety of organisms, or does it encompass other elements?
  Answer: Biodiversity includes not only the variety of organisms but also genetic diversity and ecosystem diversity.
• If you find a new organism in a pond, what features will you observe to classify it and why?
  Answer: I would observe its body structure, mode of nutrition, movement, reproduction, and cellular organization to identify its characteristics and classify it correctly.
• Why do genetic studies provide deep information about living beings?
  Answer: Genes contain hereditary information, so genetic studies reveal the evolutionary relationships, characteristics, and diversity of living organisms.
• How can changes in climate affect the biodiversity?
  Answer: Climate changes can alter habitats, reduce populations, cause species extinction, and disturb ecosystems, thereby decreasing biodiversity.

Threads of Curiosity

• New organisms are named by comparing with known species. The names may reflect their discovery place or honour scientists.
• E.g. The Purple Frog (Nasikabatrachus sahyadrensis, discovered in 2003, Kerala) is named after the Sahyadri Hills. It is an ancient underground frog that emerges during monsoon breeding. It highlights the need of biodiversity conservation in the Western Ghats.

Fossils as Evidence

• Fossils are preserved remains of plants and animals found in layers of rocks, sand and mud.
• Older layers contain simpler organisms, while newer layers show more complex forms.
• Fossils are natural records that help understand how life has changed over millions of years.

Biodiversity Under Threat

• Human activities like pollution, deforestation, resource overuse and climate change reduce biodiversity.
• When a species disappears, the dependent species may also decline in number and eventually disappear.

Bridging Science and Society

• Phumdis are unique floating grasslands in Keibul Lamjo National Park on Loktak Lake in Manipur, made of floating soil and vegetation rich in organic matter.
• They are the habitat of the endangered variety of Sangai, an endemic “dancing deer” of Manipur. This was declared extinct in 1951 but rediscovered in 1953.
• Degeneration of phumdis threatens the Sangai and is listed in the IUCN Red Data list. Efforts for the conservation of phumdis and the Sangai are ongoing.