Ans: Binomial nomenclature is the system of giving every organism a two-part scientific name — the first part is the genus name and the second is the species name, e.g., Homo sapiens for humans.

Ans: Earthworm belongs to the phylum Annelida.

Ans: Mammals are distinguished by: (1) Presence of mammary glands for feeding young ones with milk. (2) Body covered with hair or fur. (3) Warm-blooded (homeothermic). (4) Most are viviparous (give birth to live young). (5) Have a four-chambered heart. Examples: humans, whales, bats.

Ans: Cryptogams (hidden reproductive organs): do not produce seeds; reproduce by spores; include Thallophyta (algae, e.g., Ulva), Bryophyta (mosses, e.g., Funaria), and Pteridophyta (ferns, e.g., Dryopteris). Phanerogams (visible reproductive organs): produce seeds; have well-differentiated plant body with roots, stem, leaves; include Gymnosperms (naked seeds, e.g., Pinus) and Angiosperms (seeds enclosed in fruit, e.g., mango, wheat).

Ans: (1) Pisces (Fish): cold-blooded, breathe through gills, streamlined body, scales, live in water, e.g., Rohu, Shark. (2) Amphibia: cold-blooded, live on land and water, breathe through gills (larva) and lungs/skin (adult), smooth moist skin, lay eggs in water, e.g., Frog, Toad. (3) Reptilia: cold-blooded, dry scaly skin, breathe through lungs, lay eggs with hard covering on land, e.g., Lizard, Crocodile. (4) Aves (Birds): warm-blooded, body covered with feathers, forelimbs modified into wings, hollow bones for flight, four-chambered heart, lay eggs, e.g., Pigeon, Ostrich. (5) Mammalia: warm-blooded, have hair/fur and mammary glands, most viviparous, four-chambered heart, e.g., Human, Whale, Bat.

Ans: The scientific name of tiger is Panthera tigris. Scientific names are written in italics (or underlined when handwritten) because they are derived from Latin/Greek — a convention established by Linnaeus to distinguish them from common names and ensure they are universally recognized. The italic style indicates they are formal taxonomic names.

Ans: Phylum Arthropoda has the largest number of species in the animal kingdom. It includes insects, spiders, crabs, prawns, centipedes and millipedes. More than 80% of all known animal species are arthropods. Characteristics: jointed appendages, chitinous exoskeleton and open circulatory system.

Ans: Characteristic features of Kingdom Fungi: (1) Eukaryotic organisms — have membrane-bound nucleus and organelles. (2) Cell wall present but made of chitin (not cellulose). (3) Heterotrophic nutrition — mostly saprophytic (feed on dead matter) or parasitic. (4) No chlorophyll — cannot photosynthesize. (5) Body made of thread-like hyphae forming a mycelium. (6) Reproduce mainly by spores. Economically important fungi: (1) Penicillium — source of the antibiotic penicillin, used to treat bacterial infections. (2) Saccharomyces cerevisiae (yeast) — used in baking (makes bread rise) and brewing (fermentation of beer and wine). (3) Agaricus (mushroom) — edible, used as food.

Ans: Gymnosperms: (1) Seeds are naked — exposed on scales of cones, not enclosed in a fruit. (2) Flowers are absent. (3) Mostly evergreen trees or shrubs. (4) Wind-pollinated. Example: Pinus (pine tree), Cycas. Angiosperms: (1) Seeds are enclosed within a fruit — ovary wall develops into the fruit after fertilization. (2) Have true flowers (contain sepals, petals, stamens, carpels). (3) Most diverse group of plants — includes trees, shrubs, herbs. (4) Pollinated by various agents. Example: Mango (Mangifera indica), Rose (Rosa).

Ans: Phylum Coelenterata (Cnidaria) features: (1) Aquatic animals — mostly marine, some freshwater (e.g., Hydra). (2) Radially symmetrical body. (3) Diploblastic — body wall made of two layers: ectoderm and endoderm (with mesoglea between them). (4) Central gastrovascular cavity (coelenteron) with a single opening (mouth). (5) Specialized stinging cells called cnidoblasts (nematocysts) on tentacles — used for capturing prey and defense. (6) Some exist as polyp form (sessile, cylindrical; e.g., Hydra, coral), others as medusa form (free-swimming, bell-shaped; e.g., jellyfish). Some show alternation of generations (polyp → medusa → polyp). Examples: (1) Hydra — freshwater, solitary polyp. (2) Aurelia — jellyfish, marine medusa. (3) Sea anemone — sessile marine polyp. (4) Coral — colonial polyps that form coral reefs.

Ans: Need for classification: (1) There are estimated 8–10 million species of living organisms — classification makes their systematic study possible. (2) It helps understand evolutionary and phylogenetic relationships between organisms. (3) It helps in identification and naming of new species. (4) It facilitates communication and information sharing among scientists globally. (5) It helps in applied fields like agriculture, medicine, ecology and biotechnology. Basis of classification: Organisms are classified based on: (1) Cell type — prokaryote (no nuclear membrane) or eukaryote (true nucleus). (2) Number of cells — unicellular or multicellular. (3) Nutrition — autotrophic (make own food) or heterotrophic (depend on others). (4) Body organization — level of complexity (tissue/organ level). (5) Presence/absence of cell wall and its chemical nature. (6) Mode of reproduction and life history. (7) Evolutionary history (phylogeny) — increasingly used with DNA analysis.

Ans: Taxonomic hierarchy (from broadest to most specific): Kingdom → Phylum → Class → Order → Family → Genus → Species. Classification of domestic cat (Felis domesticus / Felis catus): Kingdom: Animalia — multicellular, eukaryotic, heterotrophic, no cell wall. Phylum: Chordata — has notochord (at some stage), dorsal hollow nerve cord, pharyngeal gill slits. Class: Mammalia — warm-blooded, has fur/hair, 4-chambered heart, mammary glands, viviparous. Order: Carnivora — flesh-eating mammals with specialized teeth (carnassial teeth); e.g., dogs, bears, lions also here. Family: Felidae — the cat family; retractile claws, adapted for hunting; e.g., tigers, lions, leopards. Genus: Felis — small cats; domestic cat, wildcat. Species: catus (or domesticus) — the domestic cat specifically; can interbreed with other Felis species. Scientific name: Felis catus. The hierarchy shows that as we go from Kingdom to Species, the number of shared characteristics increases and the number of organisms in the group decreases. Species is the smallest and most specific group.