Ecosystems and Biodiversity Questions and Answers

Answer: C

The proposed new epoch is the Anthropocene.

The term, popularised by Paul Crutzen around 2000, describes a period in which human activity, through climate change, land use, pollution and extinctions, has become a dominant force on Earth's geology and ecosystems. It was proposed as the youngest epoch of the Quaternary period, following the Holocene, though it has not been adopted as a formal unit of the geological time scale.

The Holocene is the current formal epoch, beginning about 11,700 years ago after the last glacial period. The Paleocene and Eocene are early epochs of the Paleogene, long before humans.

Answer: A

Tropical deciduous forests are known as monsoon forests.

They grow where rainfall is seasonal, roughly 70-200 cm a year, falling mainly in the monsoon months. The trees, such as teak and sal, shed their leaves in the dry season to save water, which is why they are deciduous. They are the most widespread forest type in India.

Mangrove forests grow in tidal coastal swamps, such as the Sundarbans. Montane forests are the altitude-zoned forests of mountains. Temperate forests grow in mid-latitudes or at higher elevations with cool climates, not in the tropical monsoon belt.

Answer: D

The phenomenon is co-extinction.

When a host species goes extinct, species that depend on it obligatorily disappear with it. Examples are parasites restricted to one host, or a plant whose only pollinator is lost. Co-extinction is counted among the major causes of biodiversity loss, together with habitat loss, over-exploitation and invasive species.

Aquaculture is the farming of aquatic organisms. Fragmentation is the breaking of a continuous habitat into isolated patches. Invasion is the spread of an introduced species that harms native ones. None of these describes extinction passing from a host to its dependants.

Answer: A

The adaptation is an impervious integument.

Both groups have a body covering that keeps water in. Reptiles have dry skin covered with keratin scales, and insects have a chitinous exoskeleton coated with a waxy layer. These coverings greatly reduce evaporation through the body surface, which lets these animals live in deserts and other dry habitats.

Fur and hairs belong to mammals, not reptiles or insects; fur mainly insulates against heat or cold. Thorns are a plant feature that reduces grazing and, as reduced leaves, transpiration. None of these is the common feature of reptiles and insects.

Answer: D

The permanently frozen ground is called permafrost.

In the tundra, the ground below a shallow surface layer stays frozen all year. Only the top few centimetres to a metre, the active layer, thaws in the short summer. Because meltwater cannot drain through the frozen layer, the surface becomes boggy, and deep-rooted trees cannot grow, which is why the tundra is treeless.

Frost is ice crystals deposited on surfaces when the temperature falls below freezing. 'Ice frost' and 'snow frost' are not terms for frozen subsoil. Only permafrost names ground that remains frozen for two or more consecutive years.

Answer: C

The correct sequence is Diatoms → Hydrilla → Wolffia → Cyperus → Populus.

This is the hydrosere, the succession that starts in open water and ends in forest:

1. Phytoplankton stage: diatoms and other microscopic algae.
2. Submerged plant stage: rooted plants under water, such as Hydrilla.
3. Floating plant stage: plants such as Wolffia on the surface.
4. Reed-swamp and sedge-meadow stages as the water becomes shallow: Cyperus and other sedges.
5. Woodland and climax forest: trees such as Populus.

Options starting with Cyperus or Hydrilla miss the plankton pioneer stage, and the option ending with diatoms runs the succession backwards. The option with Wolffia before Hydrilla puts the floating stage before the submerged stage.

Answer: B

The key takes a niche to be the functional role played by the organism where it lives.

This is Charles Elton's definition: the habitat is an organism's 'address', while its niche is its 'profession', what it does in the community, including what it eats, what eats it and how it affects energy flow and nutrient cycling.

The range of temperature an organism needs is only one dimension of its niche, its tolerance range. All the biological and physical factors around it describe its environment or habitat. The last option, how it uses the range of conditions, describes part of what makes up the niche in Hutchinson's fuller definition, but the key follows the standard textbook definition of the niche as functional role.

Answer: A

The key's answer is Taiga forest, meaning coniferous forest.

5,300 ft is about 1,600 m. In the Himalaya the forests change with altitude: tropical and subtropical forests on the lower slopes, then, from roughly 1,500 m upwards, temperate forests in which conifers such as chir pine, blue pine, deodar, spruce and fir become dominant. Taiga is the name of the boreal coniferous forest, and the paper uses it for these needle-leaved forests.

Moist tropical forests and dry deciduous forests belong to the foothills and plains, well below this altitude. 'Deciduous forest' is too general for the coniferous belt, which is why the key prefers the coniferous (taiga) option.

Answer: B

The correct sequence is Solar energy → Green plants → Herbivores.

Energy enters an ecosystem when green plants (producers) capture sunlight in photosynthesis. It passes next to herbivores (primary consumers), which eat the plants, and only after that to carnivores. The flow is one-way, and about 90% is lost as heat at each step, the ten per cent law.

Solar energy → Green plants → Carnivores skips the herbivore level, since carnivores do not eat plants. Solar energy going straight to herbivores or carnivores leaves out the producers, and animals cannot use sunlight directly. Carnivores before herbivores reverses the food chain.

Answer: C

The Indian rhino lives naturally in Kaziranga National Park, Assam.

Kaziranga, a World Heritage Site on the floodplains of the Brahmaputra, holds about two-thirds of the world's greater one-horned rhinoceroses. The 2022 census counted 2,613 there. Its tall grasslands and wetlands are the habitat the species needs.

Corbett National Park in Uttarakhand is known for tigers and elephants. The Sundarbans are mangrove forests known for the Royal Bengal tiger. Kanha National Park in Madhya Pradesh is known for the hard-ground barasingha and tigers. None of the three has a wild population of Indian rhinos.