Diversity in Living World – Long Answer Type Questions

Diversity in the living world — often called biodiversity — refers to the wide variety of living organisms found on Earth: plants, animals, fungi and microorganisms. This diversity exists at many levels: different species, different ecosystems and genetic variation within species. Biodiversity is important because it provides food, oxygen, medicines and raw materials; it maintains ecological balance through food chains and nutrient cycles; and it supports ecosystem services such as pollination and soil formation. Preservation of diversity ensures stability, resilience and sustained resources for human well-being and survival of other organisms.

In a school garden you might find: (a) a tall mango tree with a deep root system and thick trunk showing adaptation for sunlight capture and structural support; (b) creeping plants like pumpkin that spread across the ground to quickly cover soil and use runners to capture resources; (c) insects such as ants and butterflies showing animal diversity — butterflies adapted to fly and pollinate flowers while ants adapted to live in colonies and transport food. These examples illustrate differences in form, mode of life and how organisms are adapted to their habitats for food, reproduction and survival.

Biodiversity benefits humans and ecosystems in many ways. Plants supply food (grains, fruits, vegetables) and oxygen through photosynthesis; animals provide meat, milk, wool and labour; microorganisms are used in food processing (yeast in bread), medicine (antibiotics from microbes) and waste recycling. Biodiversity maintains soil fertility, pollinates crops (bees, butterflies), and controls pests through natural predators. It also offers raw materials for industries and contributes to cultural and recreational values. Loss of biodiversity can lead to ecosystem collapse, reduced food security and fewer options for medicines and resources.

A habitat is the natural environment where an organism lives and obtains its needs—food, shelter, water and mates. For example, a pond habitat supports aquatic life like fishes and aquatic plants adapted to live and breathe underwater; a desert habitat supports cacti and desert animals adapted to conserve water and tolerate heat. Each habitat provides particular resources and conditions that shape the adaptations and behaviour of the organisms found there.

Adaptation is a feature or behaviour that helps an organism survive and reproduce in its particular habitat. Plant examples: (a) cactus has thick, fleshy stems that store water and spines that reduce water loss and deter herbivores; (b) floating leaves of water lilies have large surface area to absorb sunlight and stomata on the upper surface for gas exchange. Animal examples: (a) fish have gills for extracting oxygen from water and fins for swimming; (b) camels have long eyelashes and nostrils that close to keep out sand and hump to store fat for energy during scarce food/water conditions.

Decomposers such as fungi and many bacteria break down dead plants, animals and waste materials into simpler substances. This process releases nutrients like nitrogen, phosphorus and potassium back into the soil, making them available for plants to use. Without decomposers, dead matter would accumulate and nutrients would be locked away, disrupting nutrient cycles and reducing soil fertility. Examples include mushrooms breaking down leaf litter and soil bacteria decomposing animal remains; both support healthy ecosystems and agricultural productivity.

All living organisms share key characteristics: (a) Growth — increase in size or number of cells; (b) Nutrition — obtaining and using food for energy and growth; (c) Respiration — releasing energy from food; (d) Movement — locomotion or internal movement of parts; (e) Sensitivity — responding to stimuli/environmental changes; (f) Reproduction — producing new individuals to continue the species; (g) Excretion — removal of metabolic wastes. These processes together distinguish living organisms from non-living things.

Reproduction is necessary so species can continue to exist over generations and maintain population numbers. It ensures genetic information is passed on and allows for variation and adaptation over time. Two basic ways organisms reproduce are: (a) Sexual reproduction where two parents contribute genetic material (e.g., flowering plants producing seeds after pollination; animals mating to produce offspring), and (b) Asexual reproduction where a single organism produces offspring genetically identical to itself (e.g., yeast budding, some plants via runners). Each method has advantages depending on ecological conditions.

Unicellular organisms consist of a single cell that performs all life functions; examples include many bacteria and protozoa. Multicellular organisms are made of many cells specialized for different functions; examples include plants and animals. Key differences: unicellular organisms show all life processes within one cell and often reproduce quickly, while multicellular organisms have specialized cells, tissues and organs enabling greater complexity and division of labour. Multicellular life forms usually achieve larger size and more complex behaviours.

Movement in animals is usually locomotion — entire bodies move from place to place using limbs, fins or wings (e.g., a horse walks, a bird flies). Plants generally do not move their whole bodies but exhibit movements of parts: leaves turning toward light (phototropism), opening and closing of flowers, or rapid movements like the folding of touch-sensitive leaves in Mimosa pudica. Plant movements are often growth-related or responses to stimuli and are usually slower than animal locomotion.

Respiration is the process by which organisms break down food to release energy required for life processes such as growth, movement and repair. In aerobic respiration, oxygen is used to oxidize glucose producing carbon dioxide, water and energy. Some organisms also respire anaerobically without oxygen (e.g., some bacteria and yeast). Energy released during respiration powers cellular activities, making respiration essential for survival.

Sensitivity (responsiveness) is the ability to detect and react to environmental stimuli. In plants, sensitivity is shown by movements and growth responses such as leaves curling when touched (Mimosa), roots growing toward moisture (hydrotropism), and stems bending toward light (phototropism). These responses help plants survive by maximizing resources (light, water) and avoiding harm.

A typical flowering plant has roots (absorb water/minerals, anchor plant), stem (supports plant, transports water and nutrients between roots and leaves), leaves (photosynthesis and gas exchange), flowers (reproductive organs where pollination and fertilization occur), fruits (protect seeds and aid in seed dispersal), and seeds (contain embryo for next generation). Each part is specialized to perform tasks that help the plant survive, reproduce and disperse offspring.

Photosynthesis is the process by which green plants, algae and some bacteria convert sunlight, carbon dioxide and water into glucose (food) and oxygen, using chlorophyll. It is crucial because it is the primary source of organic matter for nearly all organisms and provides oxygen for respiration. Photosynthesis thus forms the base of most food chains and drives the energy flow in ecosystems, making life on Earth possible.

Plants by habit include: (a) Trees — tall, woody plants with a single main trunk and long lifespan (e.g., banyan); (b) Shrubs — medium-sized woody plants with multiple stems from the base (e.g., rose); (c) Herbs — soft, green plants with short lifespan and non-woody stems (e.g., coriander); (d) Climbers — plants that need support to grow upward and have tendrils or twining stems (e.g., pea); (e) Creepers — plants that spread along the ground with long prostrate stems (e.g., pumpkin). These categories help identify plants based on form and growth habit.

In flowering plants, pollination transfers pollen from anther to stigma. After successful pollination, pollen germinates and a pollen tube grows down the style carrying male gametes to the ovule in the ovary. Fertilization occurs when a male gamete fuses with the egg cell to form a zygote; the zygote develops into an embryo while the ovule matures into a seed. The ovary becomes the fruit that encloses the seed(s).

Stomata are small openings on the surface of leaves (mostly underside) surrounded by guard cells. They allow exchange of gases — carbon dioxide enters for photosynthesis, oxygen and water vapour exit. Stomata regulate transpiration and gas exchange by opening and closing, helping plants maintain water balance while obtaining the CO₂ needed for photosynthesis.

Animals are commonly classified based on the presence or absence of a backbone. Vertebrates have a backbone (spinal column) and include groups such as mammals (e.g., cow) and birds (e.g., sparrow). Invertebrates lack a backbone and include insects (e.g., butterfly) and earthworms. This basic division helps students understand major structural differences and evolutionary lines among animals.

Bird adaptations include: (a) Feathers — provide insulation, enable flight and aid in courtship displays; (b) Hollow bones — make the skeleton light, facilitating flight; (c) Beaks — varied shapes adapted for feeding (e.g., a sharp beak for tearing meat, a long curved beak for probing nectar). These features help birds obtain food, escape predators and occupy diverse habitats from forests to wetlands.

Aquatic animals show adaptations such as streamlined bodies to reduce water resistance (fish), gills to extract dissolved oxygen (fish), fins for swimming and maintaining balance, and sometimes breathing adaptations (e.g., dolphins use lungs but surface for air). Aquatic plants may have air spaces to float (e.g., water lily). These adaptations enable feeding, movement and respiration in water environments.

Herbivores eat plants (e.g., cow) and often have flat teeth for grinding plant material. Carnivores eat other animals (e.g., lion) and possess sharp incisors and canines for tearing flesh. Omnivores eat both plant and animal matter (e.g., human, bear) and have mixed dentition suited for varied diets. Body structure, digestive system length and teeth types reflect dietary habits and ecological roles.

Animals maintain ecological balance by participating in food chains and webs — herbivores consume plants, carnivores control herbivore populations, and decomposers recycle dead organic matter. Pollinators like bees help in plant reproduction, while predators regulate prey numbers preventing overgrazing. Scavengers and decomposers clean up dead material, returning nutrients to soil. Each group’s interactions sustain ecosystem stability and biodiversity.

Fungi are a separate group of organisms that obtain food by absorbing nutrients from dead or living organisms. They lack chlorophyll and therefore do not perform photosynthesis, which differentiates them from plants. Fungi may be multicellular (mushrooms) or unicellular (yeast), have cell walls made of chitin, and reproduce by spores. Their role as decomposers is vital for nutrient cycling in ecosystems.

Microorganisms are beneficial in many processes: bacteria help in making curd, yeast helps in bread baking and fermentation, and microbes are used in antibiotic production and sewage treatment. They are harmful when pathogenic strains cause diseases such as typhoid, flu or plant infections. Good hygiene and proper food handling reduce harmful effects while beneficial microbes are harnessed for food production, medicine and environmental management.

Fungi and bacteria decompose dead organic matter into simpler inorganic substances that enrich soil nutrients. This recycling returns nitrogen, phosphorus and other elements for plant use. A classroom activity: set up two small sealed jars containing equal amounts of dead leaves — one with a tiny amount of soil (containing decomposers) and one sterilized — observe after weeks to see faster decomposition in the jar with soil and microbial activity. Discuss observations linking microbes to decomposition.

The aim of classification is to arrange living organisms into groups so they can be studied, identified and remembered easily. At an elementary level, classification groups organisms based on visible, shared characteristics such as body structure, mode of nutrition (producer, consumer, decomposer), presence or absence of backbone and habitat. The principles involve observing similarities and differences and grouping organisms that share common features to form a logical system that helps communication and study.

Choose five organisms (e.g., mango tree, grass, earthworm, sparrow, mushroom). Create a table listing observable features: makes own food? (yes/no), has backbone? (yes/no), habitat (soil/tree/air). Classify: mango and grass → plants (producers); sparrow → vertebrate animal (consumer with backbone); earthworm → invertebrate animal; mushroom → fungus (decomposer, no chlorophyll). Criteria used include mode of nutrition, structural features and habitat, which are simple and effective for Class 6 classification.

Classification helps identify beneficial and harmful organisms quickly, aiding pest control and crop selection. Example 1: Classifying insect pests enables targeted biological or chemical control measures without harming beneficial insects like pollinators. Example 2: Recognizing nitrogen-fixing bacteria and legumes helps farmers rotate crops to improve soil fertility naturally. Thus classification informs management practices that are efficient and environmentally friendly.

Suggested activities: (a) Make a collection and labelled chart of 15 local plants and animals with their classification; (b) Observe bread mould under teacher supervision to study fungi and draw observations; (c) Set up a simple food chain chart from a local habitat; (d) Conduct a leaf stomata observation using prepared slides to learn about gas exchange; (e) Prepare flashcards for different organisms and quiz classmates on their group and habitat. These activities reinforce observation and classification skills.

Exam strategy: begin long answers with a clear definition or topic sentence, follow with 3–4 organised points or short paragraphs, include examples and, where appropriate, a labelled diagram or table to illustrate. Use headings or bullets for clarity, keep language simple and factual, and conclude with a one-line summary. Practice writing timed answers to improve clarity and completeness under exam conditions.