Ecosystems and Biodiversity Questions and Answers

Answer: D

A lentic ecosystem is a Lake.

Freshwater habitats are divided by water movement. Lentic systems (from the Latin lentus, slow or sluggish) are standing waters: lakes, ponds, reservoirs and swamps. Lotic systems (from lotus, washed) are flowing waters.

A river, a stream and flowing water in general are all lotic habitats, with current, high oxygen and organisms adapted to cling or swim against the flow. Only the lake is standing water, with layering by temperature and plankton-based food chains.

Answer: D

The cycle with biological fixation is Nitrogen.

Atmospheric nitrogen (N₂) is inert, and most organisms cannot use it. Certain prokaryotes, Rhizobium in legume root nodules, free-living Azotobacter and cyanobacteria such as Anabaena, carry the enzyme nitrogenase and convert it to ammonia. This step, biological nitrogen fixation, is what 'biological fixation' means in the nutrient-cycle sense.

The phosphorus cycle is sedimentary, with no gaseous form to fix; phosphate is released by weathering. Oxygen is returned by photosynthesis rather than fixed. Plants do take up carbon dioxide, a process sometimes also called carbon fixation, but the standard textbook usage the question follows reserves biological fixation for nitrogen.

Answer: D

Geographically restricted species are called Endemics.

An endemic species occurs naturally in only one defined region and nowhere else, such as the Nilgiri tahr in the Western Ghats or the lion-tailed macaque. Endemism is one of the criteria for identifying biodiversity hotspots.

The other terms describe status, not range. A rare species has a small population, which may be widely scattered. An extinct species no longer exists anywhere. An endangered species faces a high risk of extinction in the IUCN categories. An endemic species may be common within its small range.

Answer: C

The fern used in paddy fields is Azolla.

Azolla is a small floating water fern whose leaves house the nitrogen-fixing cyanobacterium Anabaena azollae. Grown in flooded rice fields, it fixes atmospheric nitrogen and, when it decomposes or is incorporated, releases it to the crop, so it is used as a biofertiliser that can raise yields and cut the need for urea.

Marsilea (spelled Marselia in the paper) is a rooted aquatic fern with no such partner. Salvinia is a floating fern that becomes a troublesome weed. Ariadnaesporites is the name of a fossil spore, not a living crop aid.

Answer: A

The Ramsar Convention aims at saving Wetlands.

The Convention on Wetlands of International Importance, especially as Waterfowl Habitat, was signed at Ramsar in Iran in 1971 and came into force in 1975. It commits member countries to the conservation and wise use of wetlands and to designating sites for the List of Wetlands of International Importance. India joined in 1982.

Endangered animals are the concern of CITES (trade in endangered species) and the Convention on Migratory Species, and wild habitats in general come under the Convention on Biological Diversity. Ramsar covers only wetlands, so 'All of the above' is too broad.

Answer: B

The correct sequence is Producers \(\rightarrow\) Consumers \(\rightarrow\) Decomposers.

Energy enters an ecosystem when producers, green plants and algae, capture sunlight by photosynthesis. Herbivores eat the producers and carnivores eat the herbivores, passing on part of that energy at each step. Dead bodies and wastes from every level are finally broken down by decomposers, bacteria and fungi, which release the last of the energy as heat and return nutrients to the soil.

Energy flow is one-way and begins with the producers, so any sequence starting with consumers or decomposers is wrong. Producers to decomposers to consumers skips the grazing chain that carries most energy upward.

Answer: B

The process is called Antibiosis.

Antibiosis is an antagonistic interaction in which one microorganism releases metabolic products that inhibit or kill others. In soil, actinomycetes such as Streptomyces and fungi such as Penicillium suppress competitors this way, and the effect is used in biological control of plant pathogens.

Antibiotics are the substances involved, not the process. Antibodies are proteins made by the vertebrate immune system, and antigens are the foreign molecules that trigger their production; neither describes an interaction between soil microbes.

Answer: D

Tropical savannas are grasslands with scattered trees.

The savanna biome lies between tropical forest and desert, with a long dry season and a wet season. Fire, grazing and drought keep trees from forming a closed canopy, so a continuous cover of grasses is dotted with drought-tolerant trees such as acacias and baobabs, as in the African savannas.

Succulent life forms are typical of deserts. Grasses as the dominant cover without trees describe temperate grasslands such as the prairies and steppes. A climax of trees and herbs describes a forest. Only the mixed grass and scattered tree cover fits the savanna.

Answer: C

The statement that is not a principle is Ecological complexity is bad.

Michael Soule's normative postulates of conservation biology (1985) state that the diversity of organisms is good, that the untimely extinction of populations and species is bad, that ecological complexity is good, that evolution is good, and that biotic diversity has intrinsic value.

The paper's option B, worded 'ultimately extinction', is the untimely-extinction postulate, and options A and D appear in the list as written. Only the claim that ecological complexity is bad contradicts it, since conservation aims to preserve that complexity.

Answer: B

The correct matching is (a)-(3), (b)-(2), (c)-(1), (d)-(4).

• Autecology studies a single species, or an individual organism, in relation to its environment: (3).
• Synecology studies groups of organisms, that is communities, and their interrelationships with the environment: (2).
• Biome ecology works at the largest scale, the interactions of several biological communities with the environment over a region: (1).
• Ecosystem ecology studies all the organisms of an area together with their physical environment, as one functioning system: (4).

Any code that pairs autecology with anything other than the single-species description is wrong at once, which removes the options starting with (4) or (1). The remaining code with (b)-(1) gives synecology the multi-community scale that belongs to biome ecology.