Biogeography & Ecosystems

* 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.

Statement 1 is correct. The Earth's magnetic field does reverse polarity every few hundred thousand years, on average. Statement 2 is incorrect. The early Earth's atmosphere did not have significant oxygen and likely had a lot of carbon dioxide and other greenhouse gases. Statement 3 is correct. The rise of photosynthetic organisms like cyanobacteria significantly increased the amount of oxygen in the atmosphere over time. Therefore, the correct answer is (c) 1 and 3 only.

Statement 1 is correct: Butterflies are vital pollinators for many flowering plants. A decline in their population can lead to reduced pollination success, affecting fruit and seed production. This, in turn, can disrupt plant communities that rely on butterflies for pollination, potentially impacting entire ecosystems. Statement 2 is incorrect: While some butterfly species may interact with fungi, a decline in butterfly populations is unlikely to cause a drastic increase in fungal infections on cultivated plants. Factors like humidity, temperature, plant health, and fungicide use play a far more significant role in the spread of fungal diseases than butterfly populations. Statement 3 is correct: Butterflies are an essential part of the food web, serving as prey for wasps, spiders, birds, and other insectivorous species. A sharp decline in butterfly populations could negatively impact these predators, disrupting the ecological balance and potentially leading to cascading effects on biodiversity.

Sathyamangalam Wildlife Sanctuary and Tiger Reserve is a protected area and Tiger Reserve along the Western Ghats in the Indian state of Tamil Nadu. Largest among the four tiger reserves (Kalakad-Mundanthurai, Annamalai, Mudumalai and Sathyamangalam) in Tamil Nadu, STR is a significant wildlife corridor in the Nilgiri Biosphere Reserve between the Western Ghats and the rest of the Eastern Ghats, serving as a genetic link to contiguous protected areas including the Biligiriranga Swamy Temple Wildlife Sanctuary, Sigur Plateau, Mudumalai National Park and Bandipur National Park.

Statement 1 is correct: Reduced or zero tillage of the land minimises soil disturbance, promoting better water retention. Less disturbed soil creates a more compact surface that reduces evaporation and allows rainwater to infiltrate deeper into the ground. Statement 2 is incorrect: Applying gypsum before irrigating the field Gypsum (calcium sulfate) is a soil amendment that can improve soil structure and drainage in some situations. However, it doesn't directly conserve water. In some cases, excessive gypsum application might even increase the leaching of nutrients and salts. Statement 3 is correct: Allowing crop residue to remain in the field Leaving crop residue on the soil surface acts like a mulch. This mulch helps suppress weeds, reduces soil erosion, and minimises water evaporation from the soil surface.

Statement 1 is correct: Kharai camels can swim up to three kilometers in seawater. This rare trait allows them to reach offshore mangrove islands, where they forage for food. Statement 2 is correct: Their name "Kharai" comes from the Gujarati word for "salty" because they primarily graze on saline plants and mangroves. This dietary adaptation allows them to thrive in the harsh coastal environment. Statement 3 is incorrect: Kharai camels are herded by local communities (Maldhari) in the Kutch region of Gujarat. Their milk is consumed, and male calves are sometimes sold.
Hence, the correct answer is option A.