2025 IJMB BIOLOGY ANSWERS ================================================== THEORY ANSWERS (6a) Angiosperms, commonly known as flowering plants, represent the most diverse and widespread group of land plants, comprising over 300,000 species, including crops like rice, wheat, and ornamentals like roses. They are distinguished by their reproductive structures, flowers, which contain male stamens and female pistils, facilitating pollination by insects, wind, or other agents. A unique feature is double fertilization, where one sperm fertilizes the egg to form the embryo, while another fuses with polar nuclei to create the endosperm, a nutrient-rich tissue for the developing seed. This process occurs within an ovary, which develops into a fruit enclosing the seed, enhancing seed dispersal and protection. Angiosperms possess advanced vascular tissues—xylem for water and mineral transport, and phloem for nutrient distribution—allowing them to grow into large trees, shrubs, or herbs. Their evolutionary success is attributed to efficient reproduction, adaptability to various climates, and symbiotic relationships with pollinators. Economically, they are vital, providing food, timber, medicines (e.g., aspirin from willow), and textiles, making them foundational to human civilization and ecosystems worldwide. (6b) Alternation of generation is a life cycle characteristic of plants and some algae, involving a regular alternation between two distinct multicellular phases: the diploid sporophyte and the haploid gametophyte. The sporophyte, which produces spores through meiosis, is the dominant phase in vascular plants like angiosperms, where it forms the familiar plant body (e.g., stem, leaves, flowers). These spores germinate into the gametophyte, a smaller haploid phase that produces gametes (sperm and eggs) via mitosis. Fertilization of gametes restores the diploid sporophyte, completing the cycle. In bryophytes (e.g., mosses), the gametophyte is dominant, with the sporophyte dependent on it, while in angiosperms, the gametophyte is reduced to structures like pollen and the embryo sac within the flower. This alternation ensures genetic diversity by separating spore and gamete production, adapting plants to terrestrial environments by balancing reproductive and vegetative phases. The cycle’s complexity, especially in seed plants, supports their evolutionary success and ecological dominance. ================================================== (5a) Photosynthesis is the process by which green plants and some other organisms use sunlight to synthesize nutrients from carbon dioxide and water. Photosynthesis in plants generally involves the green pigment chlorophyll and generates oxygen as a by-product. (5b) Vascular tissue is a complex conducting tissue system in plants, primarily responsible for the transport of water, minerals, and nutrients throughout the plant body. It is a defining characteristic of vascular plants (tracheophytes), enabling them to grow to larger sizes and colonize diverse terrestrial environments. THERE ARE TWO MAIN TYPES OF VASCULAR TISSUE: (i) Xylem: Primarily responsible for the upward transport of water and dissolved minerals from the roots to the rest of the plant. It also provides structural support. Xylem is composed of several cell types, including tracheids and vessel elements (which form the main conduits for water), as well as parenchyma and fibers. (ii) Phloem: Primarily responsible for the translocation of sugars (produced during photosynthesis) from leaves to other parts of the plant where they are needed for growth or storage. Phloem consists of sieve-tube elements (the conducting cells), companion cells (which support the sieve-tube elements), parenchyma, and fibers. These two tissues are typically arranged together in vascular bundles, which can be found in roots, stems, and leaves, forming a continuous transport network throughout the plant. ================================================== (4a) View Image here (4b) Types of Lichens (i) Crustose: Grow flat and tightly attached to surfaces (e.g., rocks). (ii) Foliose: Leaf-like, loosely attached with a lobed structure (e.g., on tree bark). (iii) Fruticose: Shrubby or hair-like, three-dimensional growth (e.g., reindeer moss). - Range Forms Lichens thrive in diverse habitats, from arid deserts to arctic tundra, indicating a wide ecological tolerance, often ranging from 0°C to 30°C and varying humidity levels ================================================== (3) (i) Symbiosis: A close and long-term interaction between two different biological species, where at least one benefits (e.g., mutualism, commensalism, parasitism). (ii) Halophytes: Plants adapted to grow in high-salinity environments, such as salt marshes, by tolerating or excluding salt. (iii) Biological control: The use of natural enemies (e.g., predators, parasites) to manage pest populations, reducing the need for chemical pesticides. (iv) Pollution: The introduction of harmful substances or energy (e.g., chemicals, noise) into the environment, causing adverse effects on ecosystems ================================================== (2) (FILL THE GAPS CORRECTLY) i. ferns ii. amyloplast iii. aestivation iv. isogamy v. ascospores vi. bacilli vii. rhizoids viii. psilophyta ix. prokaryotes x. mycelium ==================================================