12. Short and Long Answer Questions: Patterns in Life: Diversity and Classification

Short Answer Type Questions

Ques 1: What is biodiversity? Why is it essential for the stability of life on Earth?

Ans: Biodiversity refers to the immense variety of living organisms and the habitats they occupy on Earth – from microscopic bacteria to giant trees, from glowing jellyfish to soaring eagles. It is essential for the stability of life because every organism plays a role in keeping nature stable and functioning. For example, microscopic algae in the oceans release most of the oxygen we breathe; fungi and bacteria decompose fallen leaves and convert waste into manure, making the soil fertile; and birds, bees, and bats pollinate flowers, while plants capture sunlight to prepare food that supports nearly all life on the planet.

Ques 2: What are endemic species? Give two examples of endemic species found in India.

Ans: Endemic species are those that are restricted to particular regions of the world and are not found naturally anywhere else. India, with its diverse habitats ranging from mountains and deserts to rainforests and coral reefs, is home to many such species.
Two examples of endemic species found only in India are:
(i) Nilgiri tahr – a wild mountain goat found in the Nilgiri Hills; and
(ii) Nepenthes khasiana – the Indian variety of the pitcher plant found in the North-East. Another example is Neelakurinji, a flowering plant endemic to the Western Ghats.

Ques 3: What is biological classification? State any four benefits of classifying living organisms.

Ans: The scientific system of grouping living organisms based on their similarities and differences in a systematic manner is called biological classification. Four benefits of classification are:
(i) It makes the study of living organisms more organised and systematic
(ii) It helps us understand the similarities and differences among living beings
(iii) It helps in identifying and naming newly discovered organisms
(iv) It supports biodiversity conservation by identifying organisms that are under threat of extinction, and allows scientists all over the world to discuss organisms using a common system.

Ques 4: Trace the development of classification systems from Aristotle to Whittaker, naming the scientists and the kingdoms they proposed.

Ans: Classification systems have evolved over time as knowledge expanded. Aristotle (4th century BCE) grouped animals based on their habitat – land, water, and air – an artificial system. Carolus Linnaeus (1758) introduced the two kingdom system, dividing all life into Plantae and Animalia. Ernst Haeckel (1866) added a third kingdom – Protista – for microscopic unicellular organisms. Herbert F. Copeland (1938) proposed the four kingdom system: Monera, Protista, Plantae, and Animalia. Finally, Robert H. Whittaker (1969) proposed the five kingdom classification – Monera, Protista, Fungi, Plantae, and Animalia – which is widely used today.

Ques 5: What are the key characteristics of Kingdom Monera? Name two useful and two harmful organisms belonging to this kingdom.

Ans: Kingdom Monera includes all unicellular prokaryotes, meaning their cells do not have a membrane-bound nucleus. They are found everywhere – in soil, water, air, hot springs, and even inside the human body. Two useful Monerans are:
(i) Lactobacillus – helps in curd formation and is beneficial to human health;
(ii) Rhizobium – fixes atmospheric nitrogen in the roots of leguminous plants, enriching the soil. Two harmful Monerans are disease-causing (pathogenic) bacteria such as those causing tuberculosis and cholera.

Ques 6: What is Kingdom Protista? How does it differ from Kingdom Monera in terms of cell structure?

Ans: Kingdom Protista includes all single-celled eukaryotes – organisms whose cells have a true membrane-bound nucleus. Examples include Amoeba, Paramecium, Chlamydomonas, and Euglena. They may or may not have a cell wall, and some are autotrophic while others are heterotrophic. The key difference from Kingdom Monera is the cell type: Monera organisms are prokaryotes – their nuclear material is not enclosed in a membrane (unbounded nucleus) – while Protista organisms are eukaryotes with a true, membrane-bound nucleus. Both are unicellular, but this fundamental difference in cell organisation places them in separate kingdoms.

Ques 7: Describe the mode of nutrition in Kingdom Fungi. What is their ecological role?

Ans: Fungi are mostly multicellular eukaryotes with cell walls made of chitin. They do not make their own food – they are heterotrophic. Most fungi absorb nutrients from dead or decaying matter through fine filaments (hyphae) that form a network called mycelium; such fungi are called saprophytes. Some fungi establish mutualistic (symbiotic) relationships with other organisms, while others live as parasites causing diseases. Their ecological role is that of important decomposers: they break down complex organic matter, such as fallen leaves, dead plants, and animals, into simpler substances and make minerals readily available in the soil. Without fungi, the decay of dead organisms would be greatly reduced, adversely affecting soil fertility and the ecological balance.

Ques 8: Distinguish between Bryophyta and Pteridophyta with respect to body structure, vascular tissue, and dependence on water.

Ans: Bryophytes (mosses and liverworts) show slight differentiation of the plant body but do not have true roots, stems, or leaves; they have root-like structures called rhizoids. They completely lack vascular tissues (xylem and phloem) for transporting water and food. They require water for reproduction as male reproductive cells must swim to reach female cells, and therefore always need a moist environment – earning them the title of ‘amphibians of the plant kingdom’. Pteridophytes (ferns) are more advanced: they possess true roots, stems, and leaves, and have well-developed vascular tissues (xylem and phloem) that transport water and food throughout the plant body. However, like bryophytes, they still depend on water for reproduction and do not produce seeds.

Ques 9: Compare Gymnosperms and Angiosperms in terms of seed formation, leaf structure, and mode of reproduction.

Ans: Gymnosperms (e.g., pine, cycads) are well-adapted to cold and dry conditions. They have needle-like or scale-like leaves that reduce water loss. Their seeds are not enclosed in fruits – the seeds are naked and often exposed on cones. Water is not required for fertilisation. Angiosperms (flowering plants, e.g., Gulmohar) have well-developed roots, stems, and leaves. They reproduce through flowers and their seeds are enclosed within fruits. Fruits attract animals and birds, aiding seed dispersal to new locations. Their reproduction depends on pollination by different agents such as insects, wind, water, or birds. Angiosperms are the most diverse plant group on the Earth because of the efficiency of their reproductive strategies.

Ques 10: What is the notochord? On the basis of its presence or absence, how is Kingdom Animalia divided?

Ans: The notochord is a flexible rod-shaped structure that provides internal support. It is one of the major criteria for classifying animals. Based on the presence or absence of the notochord, Kingdom Animalia is classified into two broad groups: (i) Non-chordata (Invertebrates) – animals that lack a notochord. They show a wide range of body organisation and include phyla such as Porifera, Cnidaria, Platyhelminthes, Nematoda, Annelida, Arthropoda, Mollusca, and Echinodermata; and (ii) Chordata – animals that possess a notochord at least once during their life. Chordata is further classified as Protochordata and Vertebrata. In vertebrates, the notochord acts as a precursor for the development of the vertebral column (backbone).

Ques 11: What is the binomial system of nomenclature? State the rules for writing a scientific name.

Ans: The binomial system of nomenclature is a universal system of giving every living organism a unique scientific name consisting of two parts – the genus name and the species name – written in Latin or a Latinised form. This system was introduced by Carolus Linnaeus in the 18th century. The rules for writing scientific names are:
(i) The name has two parts – the genus name comes first and the species name comes second
(ii) The genus name begins with a capital letter, while the species name is written entirely in small (lower case) letters
(iii) The scientific name is written in italics when printed, and underlined when handwritten. Example: Panthera tigris (tiger) and Mangifera indica (mango).

Ques 12: What are fossils? How do they act as evidence for the evolution of biodiversity?

Ans: Fossils are preserved remains of plants and animals found in layers of rocks, sand, and mud. Generally, older layers contain simpler organisms, while newer layers show more complex life forms – from giant dinosaurs to early humans and ancient plants. Fossils act as natural records that help us understand how life has changed over millions of years. They provide direct evidence that biodiversity on Earth has evolved continuously: small differences among individuals affected their survival and reproduction, accumulated over many generations, and gave rise to new forms of life. The study of fossil plants (palaeobotany), pioneered in India by Birbal Sahni, has helped link present-day plants with their ancestors and showed that life on Earth has a long, connected history.

Long Answer Type Questions

Ques 1: Describe the five kingdom classification proposed by Whittaker. Name the kingdoms, their key features, and give one example from each.

Ans: Robert H. Whittaker (1969) proposed the five kingdom classification, grouping all life forms based on cell type, level of organisation, mode of nutrition, and ecological role. The five kingdoms are:

Monera: Unicellular prokaryotes – cells with no membrane-bound nucleus. They are found in diverse environments including soil, water, air, and extreme habitats. Mode of nutrition can be autotrophic or heterotrophic. They play roles as decomposers, nitrogen fixers, and pathogens. Example: Rhizobium (nitrogen-fixing bacteria).
Protista: Unicellular eukaryotes – cells with a true membrane-bound nucleus. They may or may not have a cell wall. Some are autotrophic (produce oxygen in aquatic ecosystems) while others are heterotrophic or decomposers. Example: Amoeba.
Fungi: Mostly multicellular eukaryotes with cell walls made of chitin. They are heterotrophic and obtain nutrients by absorbing them from dead or decaying organic matter (saprophytes). They are the primary decomposers in most ecosystems. Example: Aspergillus, mushroom.
Plantae: Multicellular autotrophic eukaryotes with cell walls made of cellulose. They perform photosynthesis, form the base of most food chains, and release oxygen essential for life. Example: Spirogyra (Thallophyta), fern (Pteridophyta), rose (Angiosperm).
Animalia: Multicellular heterotrophic eukaryotes without cell walls. They depend on other organisms for food and exhibit characteristics of locomotion, rapid response to stimuli, and coordinated behaviour. Example: earthworm (Annelida), human (Vertebrata).

This classification is based on a hierarchy of features: cell type (prokaryote/eukaryote) → level of organisation (unicellular/multicellular) → cell structure (cell wall composition) → mode of nutrition (autotrophic/heterotrophic).

Ques 2: Describe the five classes of Kingdom Plantae in terms of their body structure, vascular tissue, and seed or flower formation. Trace the gradual evolution of plant features from algae to angiosperms.

Ans: Kingdom Plantae is divided into five classes showing a sequence of structural changes that help plants meet the challenges of life on land:

Thallophyta (Algae): The simplest plants – they form a thallus (an undifferentiated body) that allows direct exchange of gases, nutrients, and water with the surroundings. They lack true roots, stems, leaves, and vascular tissue. Well-adapted to aquatic habitats. Example: Spirogyra. Challenge: they cannot live on land.
Bryophyta (Mosses and liverworts): Show a transition from water to land but still depend strongly on moisture. Their body is slightly differentiated but lacks true roots, stems, or leaves; they have rhizoids instead. They completely lack vascular tissue. Require water for reproduction – called ‘amphibians of the plant kingdom’. Example: Marchantia, moss.
Pteridophyta (Ferns): First plants with true roots, stems, and leaves. Have well-developed vascular tissues – xylem (water transport) and phloem (food transport) – allowing them to live fully on land. However, they still need water for reproduction and do not produce seeds. Example: fern.
Gymnosperm: First seed-producing plants. Their seeds are naked (not enclosed in fruits) and exposed on cones. They are well-adapted to cold and dry regions with needle-like leaves that reduce water loss. Water is not needed for fertilisation. Example: pine, cycad.
Angiosperm (Flowering plants): Most advanced and diverse group. They produce flowers (to attract pollinators) and fruits (to protect and disperse seeds). Seeds are enclosed in fruits. They have the most complex body organisation with well-developed tissue systems. Example: Gulmohar, rose.

Overall, from algae to angiosperms, plant evolution shows increasing structural complexity – from an undifferentiated thallus to true organs, from no vascular tissue to xylem and phloem, and from dependence on water for reproduction to efficient pollination and seed dispersal on land.

Ques 3: Describe the major phyla of invertebrates in Kingdom Animalia, highlighting the key advancement in body organisation at each level.

Ans: Invertebrates lack a notochord and show increasing complexity in body organisation across their phyla:

Porifera (Sponges): Simplest multicellular animals. They lack tissues and organs – organisation is only at the cellular level. Numerous pores in their body allow water to continuously flow through, bringing food particles and oxygen to individual cells. Fixed in one place; found in aquatic environments. Example: sponge.
Cnidaria (Hydra, Jellyfish, Corals): First animals with tissue-level organisation. Specialised cells form tentacles for capturing prey – a major advance over Porifera which depend on water currents for food. However, they possess only a single opening for both food intake and waste removal. Example: Hydra.
Platyhelminthes (Flatworms): Show organ-level organisation and bilateral symmetry – the body can be divided into two halves along one plane with distinct head-tail and front-back regions. This allows better coordination of movement. Their flat body permits gas diffusion without specialised respiratory organs, but there is still only a single opening. Many are parasitic. Example: tapeworm.
Nematoda (Roundworms): Have an organ system level of body organisation with two openings – a mouth and an anus – making digestion more efficient. Elongated, cylindrical bodies allow movement through soil, water, or host tissues. Example: roundworm.
Annelida (Segmented Worms): Bodies are divided into distinct segments, which allows greater flexibility and more precise control of movement. They possess organ system level of organisation and a body cavity. Presence of muscles aids locomotion and a nerve cord aids control and coordination. Example: earthworm.
Arthropoda (Insects, Crabs, Spiders): Have segmented bodies with jointed appendages and a defining hard external skeleton (exoskeleton). The exoskeleton provides protection, reduces water loss, and supports powerful muscles – allowing arthropods to survive in dry and exposed environments. Example: insects, crabs.
Mollusca (Snails, Squids, Octopuses): Show organ system level organisation with soft bodies. A shell in many molluscs provides protection to the soft body. Body is segmented with a distinct head, muscular foot, and hump. Example: snail.
Echinodermata (Starfish, Sea Urchins): Possess a hard internal skeleton of calcium carbonate, providing protection and controlled movement without a notochord. Their body organisation is similar to more complex animals, showing a shift toward internal skeletal support. Example: starfish.

Ques 4: What is the hierarchical nature of classification? Explain with the example of a tiger. Also explain what is meant by genus and species in the binomial system.

Ans: Classification follows a step-by-step hierarchical order, starting from very broad groups and moving towards smaller and more specific ones. At each lower level, organisms share more common features, and every lower group is a part of the group above it. The levels of the classification hierarchy are:

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

Classification of a tiger (Panthera tigris):

Kingdom: Animalia – multicellular, heterotrophic eukaryotes.
Phylum: Chordata – possesses a notochord.
Sub-phylum: Vertebrata – possesses a vertebral column (backbone).
Class: Mammalia – warm-blooded, gives birth to young ones, feeds them milk.
Order: Carnivora – meat-eating.
Family: Felidae – cat family.
Genus:Panthera – groups closely related species sharing common features such as the ability to roar and similar skull structure. For example, Panthera tigris (tiger) and Panthera leo (lion) both belong to the genus Panthera.
Species:tigris – the species name indicates a group of organisms that consist of similar individuals capable of interbreeding and producing offspring.

Together, the genus and species name form the unique scientific name used worldwide – Panthera tigris for the tiger. This hierarchical arrangement works like an address: just as a postal address moves from the country to the exact house, biological classification moves from the kingdom to the specific species, helping scientists identify, compare, and study organisms accurately.

Ques 5: What are biodiversity hotspots? Why is India considered a biodiversity hotspot? Explain the threats to biodiversity and why its conservation is important.

Ans: Regions that support a large number of endemic species and have undergone significant habitat loss are known as biodiversity hotspots. These areas are particularly important for biodiversity conservation as they are especially rich in the number and diversity of organisms and support food webs that help ecosystems remain healthy.

India as a Biodiversity Hotspot: India’s natural landscape is highly diverse – mountains in the north, desert in the west, rainforests in the North-East, plateaus in the south, and long coastlines. Each region has distinct soil types and climatic conditions, supporting a wide variety of species. India is home to globally recognised biodiversity hotspots such as the Western Ghats, Indo-Burma region (including North-East India), the Himalayas, and Sundaland (including the Nicobar Islands). India harbours many endemic species such as the Nilgiri tahr, the Lion-tailed macaque, Nepenthes khasiana, and Neelakurinji.

Threats to biodiversity: Human activities such as pollution, deforestation, overuse of resources, and climate change are reducing biodiversity. When one species disappears, others that depend on it may also decline and eventually disappear, disrupting entire ecosystems.

Importance of conservation: Every species plays a role in nature – plants produce food and oxygen, animals pollinate flowers and disperse seeds, and microorganisms recycle nutrients. Biodiversity also provides humans with food, medicines, shelter, and livelihoods. Diversity in crop varieties reduces the risk of crop failure and strengthens food security. Protecting biodiversity hotspots is therefore critical for sustaining ecosystems and the well-being of all life on Earth.