Biogeography & Ecosystems

Continental drift: The movement of continents over millions of years has led to changes in the distribution of landmasses, altering habitats and creating opportunities for species to migrate, adapt, and diversify. It has influenced speciation events by creating barriers to gene flow and promoting allopatric speciation. Glacial cycles: Fluctuations in global climate associated with glacial-interglacial cycles have had profound effects on ecosystems and species distributions. Periods of glaciation have resulted in the expansion and contraction of ice sheets, leading to changes in sea levels, habitats, and the distribution of flora and fauna. These environmental changes have driven evolutionary processes such as adaptation, migration, and extinction. Therefore, both continental drift and glacial cycles have played significant roles in shaping the evolution of organisms.

Statement 1 is correct: Oak trees are a common sight in the temperate forests of the Himalayas, particularly at mid-altitudes. Statement 2 is correct: Rhododendrons are a diverse group of flowering shrubs that thrive in the cool, moist conditions of the Himalayas. They are known for their vibrant blooms and are a characteristic feature of the Himalayan landscape. Statement 3 is incorrect: Sandalwood is not typically found in the Himalayas. It prefers drier climates and is more commonly associated with tropical regions like southern India.

Hibernation is a state of decreased physiological activity and lowered body temperature that certain animals, such as bats and bears, undergo during the winter months to conserve energy and survive periods of limited food availability. Statement 1 is correct: Bats, especially those living in temperate regions, often enter a state of hibernation during the colder months when their food sources (insects) are scarce. Statement 2 is correct: Bears, including the brown bear, black bear, and polar bear, are well-known hibernators. Statement 3 is correct: Many rodent species, including groundhogs and chipmunks, are true hibernators. Thus, all three statements are correct.

During photosynthesis, solar energy is converted into chemical energy and stored in sugar molecule bonds. This chemical bond energy is potential (stored) energy.

Out of the three organisms listed, only 2. Nostoc is commonly used as a biofertilizer. Agaricus: This is a type of mushroom and not typically used as a biofertilizer. Nostoc: This is a filamentous, nitrogen-fixing cyanobacterium. Cyanobacteria, also known as blue-green algae, are one of the main groups of organisms used in biofertilizers due to their ability to fix atmospheric nitrogen and make it available to plants. Spirogyra: This is a green alga and not generally used as a biofertilizer.

The correct sequence of ecosystems in order of decreasing productivity is
1. Mangroves > 2. Grasslands > 3. Lakes > 4. Oceans Mangroves: These coastal ecosystems boast exceptionally high productivity due to several factors. They receive rich nutrients from both land and sea, have a warm climate, and benefit from tidal flushing that brings in fresh nutrients and removes waste products. Grasslands: These moderate-productivity ecosystems are characterized by abundant grasses and herbaceous plants. Their productivity depends on factors like rainfall, soil quality, and grazing pressure. Lakes: Freshwater lakes exhibit varying levels of productivity depending on the nutrient availability (oligotrophic - nutrient-poor, eutrophic - nutrient-rich). Generally, they are less productive than mangroves and grasslands. Oceans: Marine ecosystems, particularly open oceans, have the lowest overall productivity. Nutrient availability is limited in vast stretches of the ocean, leading to a slower rate of organic matter production compared to the other ecosystems listed.

* The lion-tailed macaque (Macaca silenus), or the wanderoo, is an Old World monkey endemic to the Western Ghats of South India. * A recent assessment for IUCN reports 3000-3500 of these animals live scattered over several areas in Tamil Nadu, Kerala, and Karnataka. * The lion-tailed macaque ranks among the rarest and most threatened primates. * IUCN Status: Endangered. * Silent Valley has the largest number of lion-tailed macaques in South India.

- Fungi and Bacteria are decomposers. They breakdown organic matter into simple inorganic substances. - Virus represents dormant life. They are metabolically inactive as long as they are outside a host body. They are not decomposers. They invade host cells and use their nucleus (DNA machinery) to carry out their life processes.

All the options are correct.
The vegetation of hot desert climate is the xerophytic type which has special characteristics to withstand very high rate of evaporation.
- They have long roots, to reach deep water sources.
- Thick barks, to reduce water loss.
- Waxy leaves, to minimize evaporation.
- Presence of thorns and little leaves, to reduce water loss.

Excretion of urea by animals - Correct: Urea (CO(NH₂)₂) contains nitrogen. When animals excrete urea, microbes in the soil convert it into ammonia, and later into nitrates and nitrites — forms usable by plants. Thus, urea adds nitrogen to the soil indirectly. Burning of coal by man - Incorrect: Burning coal releases nitrogen oxides (NOₓ) into the atmosphere, not into the soil. These contribute to air pollution and acid rain, not direct soil enrichment. Death of vegetation - Correct: When plants die, their tissues decompose. Decomposers (bacteria and fungi) break down organic matter, releasing nitrogen compounds back into the soil. Hence, this process adds nitrogen to the soil naturally.