Which biotic component of an ecosystem is present in the greatest number?
- A.Primary Consumers
- B.Producers
- C.Secondary Consumers
- D.Tertiary Consumers
Correct answer
B. Producers
Explanation
The correct answer is B, Producers. Producers, the green plants and algae, are the most numerous living part of an ecosystem because every other organism depends on them for food. They make their own food by photosynthesis using sunlight, so they form the first trophic level of every food chain. Only about 10 per cent of the energy passes from one level to the next (Lindeman's ten per cent law), so each higher level can support fewer organisms. This gives the upright pyramid of numbers in a grassland: many grass plants, fewer grasshoppers, fewer frogs, and very few snakes and hawks. A is wrong because primary consumers, the herbivores, feed on producers and are fewer than them. C is wrong because secondary consumers, the small carnivores, are fewer still. D is wrong because tertiary consumers, the top carnivores such as the tiger or eagle, are the fewest of all. Exam tip: Producer → primary consumer → secondary consumer → tertiary consumer; about 90 per cent of energy is lost at each step; in a single-tree ecosystem the pyramid of numbers is inverted.
Practice Questions
View allNTU is the unit for measuring
- A.Pressure of water
- B.Temperature of water
- C.Acidity of water
- D.Turbidity of water
Show answer
Correct answer: D. Turbidity of water
Explanation
The correct answer is D, Turbidity of water. NTU stands for Nephelometric Turbidity Unit. A nephelometer shines a beam of light through a water sample and measures how much of it is scattered sideways by suspended particles such as clay, silt, algae and microbes; the more the scattering, the more turbid, or cloudy, the water is. Turbidity is a key test for drinking water because the particles can shield germs from chlorine and other disinfectants, so water supply agencies try to keep it very low before the water reaches homes. High turbidity in a river or lake also cuts off sunlight for aquatic plants. Option A is wrong because water pressure is measured in units such as the pascal or the bar. Option B is wrong because temperature is measured in degrees Celsius or in kelvin. Option C is wrong because acidity is shown on the pH scale, where 7 is neutral and values below 7 are acidic. Exam tip: NTU = turbidity (cloudiness); pH = acidity; BOD = organic pollution, in milligrams per litre.
An inverted pyramid of biomass can be found in which ecosystem?
- A.Grassland
- B.Marine
- C.Tundra
- D.Forest
Show answer
Correct answer: B. Marine
Explanation
The correct answer is B, Marine. In the sea the producers are tiny phytoplankton. At any given moment their total mass is smaller than the mass of the zooplankton and fish that feed on them, so the pyramid of biomass stands upside down. This happens because phytoplankton grow and divide very fast and are eaten almost as quickly as they are produced, so a small standing crop can support a larger mass of consumers. The pyramid of energy, however, is always upright in every ecosystem, because energy is lost as heat at each step and only about 10 percent passes to the next level. Option A is wrong because in a grassland the grasses far outweigh the grazing animals, giving an upright pyramid. Option C is wrong because the tundra also has more plant mass than animal mass. Option D is wrong because in a forest the huge trees give a large biomass base, so the pyramid of biomass is upright, even though the pyramid of numbers there can be inverted. Exam tip: numbers can be inverted in a tree ecosystem, biomass in the sea, but energy never.
Which pollution causes Itai-Itai disease in human beings?
- A.Mercury pollution
- B.Cadmium pollution
- C.Arsenic pollution
- D.Nitrate pollution
Show answer
Correct answer: B. Cadmium pollution
Explanation
The correct answer is B, Cadmium pollution. Itai-itai disease is long-term cadmium poisoning, first noticed around 1912 in the Toyama region of Japan, where mines upstream released cadmium into the Jinzu river and it built up in the rice and water used by villagers. Cadmium damages the kidneys and makes bones soft and brittle, so patients suffered repeated fractures and severe pain in the spine and joints; the name means it hurts, it hurts in Japanese. It became one of the four big pollution diseases of Japan. Option A is wrong because mercury pollution causes Minamata disease, also from Japan, which spread through eating fish from a bay polluted with methylmercury. Option C is wrong because arsenic in groundwater causes arsenicosis, with skin lesions and cancers, as seen in West Bengal and Bangladesh. Option D is wrong because too much nitrate in drinking water causes blue baby syndrome, or methaemoglobinaemia, in infants. Exam tip: cadmium–itai-itai, mercury–Minamata, nitrate–blue baby, fluoride–fluorosis.
Match the following pairs and identify the correct code:
Biosphere Reserve Area – State
1. Nokrek – a. Odisha
2. Manas – b. Meghalaya
3. Similipal – c. Andhra Pradesh
4. Seshachalam – d. Assam
Code: 1 2 3 4
- A.b d a c
- B.b a d c
- C.b d c a
- D.d b a c
Show answer
Correct answer: A. b d a c
Explanation
The correct answer is A, b d a c. Nokrek Biosphere Reserve is in the Garo Hills of Meghalaya; Manas is in Assam along the Bhutan border; Similipal is in Mayurbhanj district of Odisha; and Seshachalam lies in the Eastern Ghats of Andhra Pradesh. Nokrek is valued as a gene pool of wild citrus, Manas is also a tiger reserve and a World Heritage Site, Similipal is known for its tigers and waterfalls, and the Seshachalam hills are home to the red sanders tree. India began creating biosphere reserves under UNESCO’s Man and the Biosphere (MAB) programme, and the Nilgiri Biosphere Reserve, set up in 1986, was the first. Option B is wrong because it places Manas in Odisha and Similipal in Assam. Option C is wrong because it puts Similipal in Andhra Pradesh and Seshachalam in Odisha. Option D is wrong because it swaps the states of Nokrek and Manas. Exam tip: Nokrek–Meghalaya, Manas–Assam, Similipal–Odisha, Seshachalam–Andhra Pradesh, and Nilgiri (1986) the first.
Match the following.
National Parks/Wildlife Sanctuaries: a. Corbett National Park, b. Sunderbans National Park, c. Bandhavgarh National Park, d. Sariska Wildlife Sanctuary
States: i. West Bengal, ii. Uttarakhand, iii. Rajasthan, iv. Madhya Pradesh
- A.a - iii, b - i, c - iv, d - ii
- B.a - iv, b - i, c - iii, d - ii
- C.a - iii, b - iv, c - ii, d - i
- D.a - ii, b - i, c - iv, d - iii
Show answer
Correct answer: D. a - ii, b - i, c - iv, d - iii
Explanation
The correct answer is D, a - ii, b - i, c - iv, d - iii. Corbett National Park in Uttarakhand is India's oldest national park; it was set up in 1936 as Hailey National Park and in 1973 became the first reserve under Project Tiger. Sundarbans National Park in West Bengal lies in the Ganga–Brahmaputra delta, has the world's largest mangrove forest and is famous for its swimming Royal Bengal tigers; it is a UNESCO World Heritage Site. Bandhavgarh National Park in Umaria district of Madhya Pradesh has one of the highest densities of tigers in India, and the white tigers of Rewa were first found in this region. Sariska in Alwar district of Rajasthan lost all its tigers by 2005, and tigers were brought back from Ranthambore from 2008. Option A is wrong because it puts Corbett in Rajasthan and Sariska in Uttarakhand. Option B is wrong because it places Corbett in Madhya Pradesh and Bandhavgarh in Rajasthan. Option C is wrong because it puts Sundarbans in Madhya Pradesh and Sariska in West Bengal. Exam tip: Corbett Uttarakhand, Sundarbans West Bengal, Bandhavgarh MP, Sariska and Ranthambore Rajasthan.