Biogeography & Ecosystems

Statement 1 is correct: Global warming poses a significant threat to methane hydrate deposits. These icy structures, found in permafrost and deep-sea sediments, can destabilize as temperatures rise, releasing methane into the atmosphere. Since methane is a potent greenhouse gas its release could create a positive feedback loop, further accelerating global warming. Statement 2 is correct: Large deposits of methane hydrate are primarily found in two locations:
1. Arctic Tundra: Permafrost soils in the Arctic hold significant methane hydrate reserves, which are at risk of melting due to rising temperatures.
2. Seafloor Deposits: Continental margins and deep ocean sediments contain vast methane hydrate reserves. Changes in ocean temperature and pressure fluctuations can trigger their release. Statement 3 is correct: After about 12 years, the methane is converted into carbon dioxide through hydroxyl oxidation. While CO₂ is a less potent greenhouse gas than methane, its longer atmospheric lifetime means it continues contributing to long-term climate change. Therefore, option (D) 1, 2 and 3 is correct.

Manas National Park (Assam): Situated on the banks of the Manas River, it encompasses a range of ecosystems including grasslands, tropical evergreen forests, and semi-evergreen forests. Namdapha National Park (Arunachal Pradesh): This park boasts diverse vegetation zones, ranging from tropical evergreen forests at lower elevations to sub-alpine meadows at higher altitudes. Neora Valley National Park (West Bengal): This park covers a range of elevations with subtropical broadleaf forests at lower levels and temperate forests at higher reaches. The Valley of Flowers National Park (Uttarakhand): On the other hand, is situated at a high altitude (3352 to 3658 metres above sea level) and falls entirely within the temperate alpine zone, known for its meadows, low-growing vegetation, and cooler climate. Hence, option D is the correct Answer.

The correct ascending order for the percentage of forest cover in the mentioned states 1. Odisha (32.34%)
2. Madhya Pradesh (25.11%)
3. Maharashtra (16.47%)
4. Chhattisgarh (41.09%) Chhattisgarh has the highest forest cover percentage, followed by Odisha, Madhya Pradesh, and Maharashtra. Hence the correct answer is option 3, i.e 3-2-4-1. (Ascending order)

Remote sensing is the process of detecting and monitoring the physical characteristics of an area by measuring its reflected and emitted radiation at a distance from the targeted area. Statement 1 is correct. Satellite images and remote sensing data can indeed be used to estimate the chlorophyll content in vegetation. This is done by measuring the reflectance of light from the vegetation. The chlorophyll in plants absorbs light for photosynthesis, and the amount of light reflected back can give an estimate of the chlorophyll content. Statement 2 is correct. Satellite images and remote sensing data can also be used to estimate greenhouse gas emissions. This is done by detecting the radiations emitted by the substances in the rice paddies. Statement 3 is correct. Satellite images and remote sensing data can be used to measure land surface temperatures as well. This is done by detecting the infrared radiation emitted by the land surface. Therefore, all three parameters can be measured or estimated using satellite images or remote sensing data.

Plants in arid environments have evolved adaptive features to minimize water loss through transpiration: - Hard and waxy leaves have a thick cuticle and fewer stomata, reducing water loss by limiting evaporation.
- Tiny leaves have a smaller surface area, which decreases the area exposed to transpiration.
- Thorns, though primarily modified branches for protection, can also replace leaves in some desert plants (e.g., cacti), further reducing transpiration by limiting leaf surface area. Therefore, the correct answer is option (d) 1, 2 and 3.

* Aral Sea: The Aral Sea was once one of the world's largest inland lakes, but due to extensive water diversion for irrigation projects, particularly from the Amu Darya and Syr Darya rivers, it has shrunk by over 75% since the 1960s. This has led to severe environmental, economic, and social consequences, including increased salinity, loss of marine life, and desertification. * Black Sea: While the Black Sea faces environmental challenges such as pollution, biodiversity loss, and reduced oxygen levels in deep waters, it has not experienced significant drying like the Aral Sea. * Lake Baikal: Lake Baikal in Russia is the deepest and oldest freshwater lake in the world, containing about 20% of the world's unfrozen freshwater supply. Although it experiences natural fluctuations in water levels, it has not undergone severe drying like the Aral Sea. Thus, the correct answer is option (d).

* Prosopis juliflora, commonly known as mesquite or thorn mimosa, frequently appears in discussions about invasive species due to its significant impact on ecosystems and biodiversity. * Originally native to Central and South America, Prosopis juliflora was introduced to various parts of Africa, Asia, and Australia for purposes like afforestation, erosion control, and fuelwood supply. * However, due to its rapid growth rate, tolerance for harsh conditions, and prolific seed production, it can become invasive. * It can outcompete native plants, disrupt ecological balances, and form dense thickets that hinder other vegetation growth. * In states like Tamil Nadu, Prosopis juliflora has been labelled an invasive species causing ecological damage. Efforts are underway to remove it from certain areas to restore native ecosystems.

Statement 1 is incorrect: High organic matter content in soil actually increases its water-holding capacity. Organic matter helps to bind soil particles together, creating pore spaces that can hold water. It acts like a sponge, absorbing and retaining moisture effectively. Statement 2 is incorrect: Soil plays a crucial role in the sulphur cycle. Soil contains various forms of sulfur compounds, including sulfates, which are essential nutrients for plant growth. Microorganisms in the soil participate in the transformation of sulfur compounds through processes like mineralization and immobilization. Statement 3 is correct: Excessive or improper irrigation practices can lead to the salinization of agricultural lands. When irrigation water contains high levels of dissolved salts, and there is inadequate drainage, these salts can accumulate in the soil over time, leading to soil salinization. This can adversely affect crop growth and productivity. Therefore, among the given statements, only statement 3 is correct.

Conservation Agriculture is a set of practices aimed at minimizing soil disturbance, maintaining permanent soil cover, and adopting crop rotations or intercropping. Avoiding monoculture practices: This does not directly fall under Conservation Agriculture. Monoculture refers to the cultivation of a single crop over a wide area. Adopting minimum tillage: Minimum or no tillage is one of the key principles of Conservation Agriculture, as it reduces soil disturbance. Avoiding the cultivation of plantation crops: This is not a part of Conservation Agriculture. Plantation crops like tea, coffee, or rubber can be cultivated using conservation agriculture practices. Using crop residues to cover the soil surface: Maintaining soil cover with crop residues or mulches is a crucial component of Conservation Agriculture. Adopting spatial and temporal crop sequencing/crop rotations: Crop rotations and intercropping are recommended practices under Conservation Agriculture to improve soil fertility and reduce pest and disease incidence. Therefore, the correct options that fall under Conservation Agriculture are 2, 4, and 5.

Most of the world's coral reefs are found in tropical waters. Coral reefs thrive in warm, shallow, clear waters with a temperature range between 18C and 34C, and they are predominantly located in the tropics. More than one-third of the world's coral reefs are located in the territories of Australia, Indonesia, and the Philippines. These countries have some of the largest and most diverse coral reef ecosystems in the world. Coral reefs host a far greater number of animal phyla compared to tropical rainforests. Coral reefs are known for their high biodiversity, hosting a wide variety of marine species, including many unique and specialised organisms. In contrast, tropical rainforests, while also highly diverse, host a relatively smaller number of animal phyla. Therefore, all three statements are correct.