Environment & Ecology Quiz: Biomes and Ecological Succession

The correct answer is A, the north eastern coast of Australia. The Great Barrier Reef stretches for well over two thousand kilometres along the Queensland coast in the Coral Sea, off the north eastern shore of Australia, and is the largest structure on earth built by living organisms. It lies there because the conditions a reef needs are all present together: shallow water on a wide continental shelf, sea temperature that stays warm through the year, clear water that lets sunlight reach the algae living inside the coral polyps, and normal salinity undisturbed by a great river. Option B is wrong because the western coast faces the cool waters of the Indian Ocean and carries only small fringing reefs. Option C is wrong because the northern coast is muddied by river discharge into the Arafura Sea. Option D is wrong because the southern coast lies in cooler temperate latitudes where reef building corals cannot grow. Remember also that reefs are called the rainforests of the sea.

The correct answer is D, Kyushu Island of Japan. Kyushu is one of the four main islands of the Japanese archipelago and is of volcanic origin, built by the eruptions of an island arc where one plate dives beneath another; Mount Aso on it has one of the largest volcanic calderas in the world. It is not a coral reef island at all. Option A is wrong as a choice because the Great Barrier Reef off the Queensland coast is the classic coral structure, the largest in the world. Option B is wrong because the Rainbow Reef of Fiji, in the Somosomo Strait, is a well known coral reef in the tropical Pacific. Option C is wrong because Swaraj Island, formerly called Havelock Island, lies in the Andaman group, where the islands are ringed by fringing coral reefs. The lesson to carry away is that tropical islands are built in two very different ways, by volcanic activity and by the slow growth of coral, and the question tests whether you can tell them apart.

The correct answer is D, the tropical savanna region. The savanna is a tropical grassland with tall coarse grass and scattered flat topped trees, and its wet season produces an enormous crop of grass. That grass supports the largest herds of grazing animals on earth, the zebra, the wildebeest, the giraffe and the antelope, and those herds in turn support the lion, the leopard and the cheetah. Because so many large mammals live there together, the savanna, especially in East Africa, is called the land of big game. Option A is wrong because the temperate grassland has short grass and has been ploughed for wheat so widely that it is called the granary of the world, and its large wild herds are long gone. Option B is wrong because the tropical monsoon region is known for deciduous forest and for rice cultivation under a seasonal rainfall regime. Option C is wrong because the hot desert has too little vegetation to feed large herds, and its animals are small and mostly nocturnal.

The correct answer is B, the taiga or boreal coniferous forest. The taiga forms an almost unbroken belt of needle leaved softwood trees, mainly pine, spruce, fir and larch, right across the northern parts of Canada, Scandinavia and Siberia, and this belt covers a greater area of land than any other biome. Its trees are conical and evergreen, their needles cut water loss in a long frozen winter, and the forest is the world's main source of softwood, newsprint and pulp. Option A is wrong because the tropical rainforest, though far richer in species, is confined to a narrow equatorial belt and covers a much smaller area. Option C is wrong because the tundra lies poleward of the taiga on a smaller ring of land and carries no trees at all, only mosses, lichens and sedges above a frozen subsoil. Option D is wrong because the savanna, though extensive in Africa, South America and northern Australia, still covers less land than the boreal forest. Do not confuse largest in area with richest in species.

The correct answer is C, the Prairies. The temperate grassland is the same biome the world over, short nutritious grass with almost no tree, but each continent gives it a local name, and the pairs are asked directly in examinations. In North America, across the central United States and the Canadian plains, it is called the Prairies, and so much of it has been ploughed for wheat that the region is known as the granary of the world. Option A is wrong because the Pampas is the temperate grassland of Argentina and Uruguay in South America, famous for cattle ranching. Option B is wrong because the Steppes form the vast grassland belt of Eurasia, running from Ukraine across Central Asia. Option D is wrong because the Veld is the grassland of the plateau of South Africa. Complete the set with the Downs of Australia and the Canterbury of New Zealand, and keep the tropical grasslands separate: the Savanna of Africa, the Llanos and Campos of South America.

The correct answer is B, lichens. A bare rock offers no soil, almost no water and no shelter, and only an organism that can survive long spells of drying and can hold on to bare stone can settle there. A lichen is exactly that, a partnership of an alga and a fungus in which the fungus grips the rock and holds water while the alga makes food. Lichens also release weak acids that eat into the rock and, with their own dead remains, form the first thin film of soil. Option A is wrong because mosses follow the lichens; they need that first film of soil and more moisture than bare rock can give. Option C is wrong because grasses come later still, after the soil is deep enough to hold roots and water. Option D is wrong because shrubs belong to a late seral stage, shortly before the tree climax. The full xerarch sequence to remember is lichen, moss, herb and grass, shrub and finally forest, and the parallel hydrarch sequence begins with phytoplankton in water.

The correct answer is B, the soil is already present. Primary succession starts on a surface that has never held life, a cooled lava flow, a bare rock or a fresh sand dune, and the slowest part of the whole process there is the making of soil: rock has to be weathered grain by grain and organic matter has to accumulate from the dead pioneers, which takes a very long time. Secondary succession starts where an existing community was destroyed by fire, flood, felling or cultivation, but the soil, with its nutrients, its seed bank and its microbes, survived. Plants can therefore root at once and the sere runs to its climax much sooner. Option A is wrong because secondary succession usually begins on land, and starting in water describes hydrarch succession, which is a different classification. Option C is wrong because secondary succession also has a pioneer community, typically fast growing weeds and grasses. Option D is wrong because climate decides which climax is reached, not how fast a sere moves.

The correct answer is C, the climax community. Succession is a directional process: each community changes the place a little, making it fit for the next, until a community arrives that is in balance with the climate of the region and can replace itself generation after generation without being replaced by another. That is the climax community, and in most of India it is some kind of forest. Option A is wrong because the pioneer community is the first to arrive on the bare site, made of hardy organisms such as lichens on rock or phytoplankton in water. Option B is wrong because a seral community is any of the intermediate communities on the way, and the whole sequence of them is called a sere. Option D is wrong because pelagic refers to the open water zone of a lake or an ocean and is a description of habitat, not a stage of succession. Frederic Clements argued that in a given climatic region succession always leads to one climax, a view called the monoclimax theory.

The correct answer is A, permafrost. In the tundra only a thin upper layer of the ground thaws in the brief summer; below it the soil stays frozen through the year, and this permanently frozen subsoil is called permafrost. It blocks the deep roots that a tree needs and it also stops water from draining away, so the surface turns into waterlogged marsh in summer. That is why the tundra carries only mosses, lichens, sedges and low flowering herbs, and no trees. Option B is wrong because podzol is the acidic, ash grey soil of the coniferous forest belt just south of the tundra, formed by the leaching of the upper layer. Option C is wrong because chernozem is the black, very fertile soil of the temperate grasslands, rich in humus and famous in the Steppes of Ukraine. Option D is wrong because laterite is the iron rich red soil of the humid tropics, formed by heavy leaching under high rainfall and temperature.

The correct answer is A, the zooxanthellae algae. A reef building coral polyp lives in a close partnership with single celled algae called zooxanthellae that live inside its own tissue. The algae photosynthesise and pass most of the food they make to the polyp, and they also give the coral its brown and green colour; the polyp in return gives them shelter and carbon dioxide. When the sea water becomes too warm or too acidic, or when it is muddied, the polyp expels these algae. The white calcium carbonate skeleton then shows through the transparent tissue, which is why the reef looks bleached, and unless the algae return the polyp starves. Option B is wrong because diatoms are free floating phytoplankton of open water and are not partners of coral. Option C is wrong because nitrogen fixing bacteria live in root nodules of legumes and in the soil. Option D is wrong because mycorrhizal fungi form partnerships with the roots of land plants, not with marine animals.