NEET Zoology - MCQ Practice Questions

Azotobacter (free-living) and Rhizobium (symbiotic with legumes) are the primary nitrogen-fixing bacteria in soil that convert atmospheric N₂ into ammonia (NH₃), making nitrogen available to plants.

Deserts are characterized by extremely low annual precipitation (less than 25 cm per year), making them the driest biomes on Earth, though tundras are also very dry.

The Western Ghats qualify as a biodiversity hotspot due to their exceptional species richness, with over 50% endemic species and significant ongoing habitat destruction from human activities.

Gause's competitive exclusion principle states that two species with identical ecological niches cannot coexist indefinitely. Classic laboratory experiments with Paramecium species demonstrated that one species outcompetes and excludes the other.

The phosphorus cycle is primarily abiotic, involving weathering of rocks, sedimentation, and geological processes, with minimal involvement of microorganisms compared to nitrogen or carbon cycles.

Asian elephants are keystone species in Indian forests because their feeding and movement patterns significantly influence forest structure, vegetation composition, and create habitats for other species.

Habitat fragmentation, resulting from urbanization, agriculture, and infrastructure development, is identified as the primary driver of biodiversity loss in India, more significant than other factors.

Energy pyramids are always upright because energy decreases at each trophic level due to metabolic losses, following the second law of thermodynamics, unlike biomass or number pyramids which can be inverted.

Directional selection operates when antibiotics kill susceptible bacteria, providing selective advantage to resistant strains, continuously shifting the population toward greater antibiotic resistance.

Community Reserves in India are established on community or private land to protect species, habitats, and ecosystems while allowing local communities sustainable use, balancing conservation with livelihood needs.

r-selected species (like insects and small rodents) typically produce many offspring with minimal parental investment and care. K-selected species (like elephants and humans) show extended parental care.

Density-independent factors (like weather, drought, floods) affect populations regardless of their density, whereas disease and competition are density-dependent as their impact increases with higher population density.

Rising sea temperatures are the primary trigger for coral bleaching, causing symbiotic algae expulsion. Climate-induced warming of coastal waters around India's coral reefs (Andaman, Lakshadweep) directly causes bleaching events.

Small, isolated populations experience increased genetic drift, loss of genetic diversity, and inbreeding depression, reducing fitness and adaptive capacity, making them highly vulnerable to extinction from random events.

Regulating services include processes like climate regulation, pollination, disease control, and water purification that maintain ecosystem functions benefiting humans, distinct from provisioning, cultural, or supporting services.

The facilitation model (Connell & Slatyer) proposes that pioneer species modify environmental conditions to make them more suitable for subsequent species, gradually changing the ecosystem toward climax community.

Deciduous trees in Indian dry and moist deciduous forests shed leaves during the dry season (March-May) as an adaptation to seasonal water scarcity, reducing transpirational water loss while maintaining survival.

With abundant resources and low initial population density, the deer population exhibits exponential growth (J-shaped curve). The carrying capacity has not yet been reached as numbers are still increasing rapidly without stabilization.

The 10% energy transfer rule states that only ~10% of energy is passed to the next trophic level; the remaining 90% is lost through respiration, heat, and excretion. This is fundamental to understanding ecosystem energy dynamics.

Lantana camara outcompetes native vegetation through superior resource acquisition and allelopathy, leading to competitive exclusion. This reduces niche availability for native species, fundamentally altering community structure and ecosystem functions like nutrient cycling.