Biogeography & Ecosystems

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.

The precipitation is so erratic that drought and fire prevent large forests from growing. - Grasses can survive fires because they grow from the bottom instead of the top. - Their stems can grow again after being burned off. - The soil of most grasslands is also too thin and dry for trees to survive.

In ecology, a niche is a term describing the relational position of a species or population in an ecosystem. More formally, the niche includes how a population responds to the abundance of its resources and enemies (e.g., by growing when resources are abundant, and predators, parasites, and pathogens are scarce) and how it affects those same factors (e.g., by reducing the abundance of resources through consumption and contributing to the population growth of enemies by falling prey to them). Gause's competitive exclusion principle says that those species having identical requirements cannot occupy the same niche indefinitely.

Statement 1 is correct: A food chain shows the linear sequence of organisms through which energy and nutrients pass, from producer → herbivore → carnivore → decomposer. Statement 2 is incorrect: Food chains are not found within the populations of a species, because technically, the food chain is the sequence of organisms through which the energy flows. Statement 3 is incorrect: A food chain does not show the number of organisms, it only shows the feeding relationship and energy flow.

Statement 1 is correct: The trees are very tall (up to 50 m or more) and grow close together, competing for sunlight. Their crowns form a dense, multilayered canopy that blocks most sunlight from reaching the ground. Statement 2 is correct: Equatorial forests are the most biodiverse ecosystems on Earth. A single hectare can host hundreds of tree species, along with diverse fauna and microorganisms. This is due to stable climate and continuous growing season. Statement 3 is correct: Epiphytes (plants growing on other plants) such as orchids, mosses, and ferns thrive here. The humid atmosphere and dense canopy support their growth on trunks and branches.

Steppes: Steppes are usually characterized by a semi-arid or continental climate. Extremes can be recorded in the summer of up to 45 °C (113 °F) and in winter, 55 °C (67°F). Besides this huge difference between summer and winter, the differences between day and night are also very great. African Savannah & North American Prairie: These regions have more rainfall and varied landscapes compared to the Steppe. Nomadic herding existed, but wasn't the sole way of life. Siberian Tundra: Colder, less rain, permafrost. Not ideal for grazing animals. Nomadic herding is less prevalent. Therefore, the Central Asian Steppe, with its extreme climate, limited rainfall, and historical dependence on nomadic herding, best fits the description in the statement.