(a) What is meant by biodiversity? Explain various means of in situ conservation of biodiversity. (20 marks) (b) Describe two…

(a) Biodiversity and in situ conservation Biodiversity is the variety of life at genetic, species and ecosystem levels. Genetic diversity is variation within a species, species diversity is number and abundance of species, and ecosystem diversity is range of habitats and ecological processes. These are measured as alpha diversity within a site, beta diversity among sites, and gamma diversity across a landscape. In situ conservation means protecting species and ecosystems in their natural habitats, so that natural selection, gene flow, pollination, predation and nutrient cycling continue. It maintains co-evolved interactions and adaptive potential, allowing populations to respond to environmental change. It differs from ex situ conservation, which maintains organisms outside their natural range in zoos, botanical gardens, seed banks or cryopreservation. In India, in situ methods include national parks such as Jim Corbett and Kaziranga, wildlife sanctuaries, biosphere reserves such as Nilgiri in the Western Ghats biodiversity hotspot, sacred groves, and community reserves. Protected areas reduce hunting, logging and conversion, while biosphere reserves combine core protection with buffer zones for sustainable use. Sacred groves and community reserves involve local institutions, reducing illegal extraction. The legal framework includes the Convention on Biological Diversity (CBD), Wildlife Protection Act 1972 and Biological Diversity Act 2002. Yet in situ conservation faces habitat fragmentation, invasive species, climate change and human-wildlife conflict, which can isolate populations and reduce genetic diversity.

(b) Laws and types of learning The two basic laws of learning are Thorndike’s Law of Effect and Law of Exercise. The Law of Effect states that responses followed by satisfying consequences are strengthened, while those followed by discomfort are weakened; this explains instrumental or operant conditioning. The Law of Exercise says that repeated association between stimulus and response strengthens the connection, though reinforcement matters more than repetition. Pavlov’s classical conditioning provides the paradigm in which a neutral stimulus becomes associated with an unconditioned stimulus; it shows acquisition, extinction and generalization. Habituation is non-associative learning in which an animal reduces its response to a repeated, harmless stimulus; Aplysia shows reduced gill withdrawal after repeated touch, and urban birds ignore traffic. Trial and error learning occurs when an animal tests responses until one produces reward, as in Thorndike’s puzzle box, where cats escape faster over trials. Latent learning is learning that occurs without obvious reinforcement and appears later when motivated; Tolman’s rats formed cognitive maps of mazes, showing internal maps guide behaviour. In India, these principles guide wildlife management, such as reducing habituation to humans and using deterrents.

(c) PCR PCR is a molecular technique that amplifies a specific DNA segment using a thermostable DNA polymerase. Its principle is primer-directed, template-dependent DNA synthesis: two short primers bind to flanking sequences, and DNA polymerase extends them, copying the target region. The reaction mixture contains template DNA, forward and reverse primers, dNTPs, buffer, Mg2+ and Taq polymerase. The working mechanism is cyclic. In denaturation at 94-95°C, double-stranded DNA separates into single strands. In annealing at 50-65°C, primers bind to complementary sequences. In extension at 72°C, Taq polymerase adds nucleotides to the 3’ ends of primers, synthesising new strands. Taq polymerase is specific for the primer-template junction and thermostable, so it withstands repeated heating. This makes PCR highly specific. Because each cycle doubles the target, amplification is exponential, approximately 2^n after n cycles. PCR is used in forensics for DNA fingerprinting, disease diagnosis such as COVID-19 RT-PCR, phylogenetics, ancient DNA studies, and genetic testing. Variants include qPCR for quantification, RT-PCR for RNA targets and digital PCR for absolute measurement. In India, PCR supports diagnostics and forensic DNA profiling.