In an ecosystem why is the number of trophic levels of a food chain usually limited ?
- A.Lower trophic level has lesser energy than the higher trophic level
- B.Because of the loss of energy at each trophic level
- C.Higher trophic level individual can control the lower ones more efficiently
- D.Limited trophic level makes a food chain less vulnerable to parasites
Correct answer
Explanation
The correct answer is B. A large part of the energy is lost at every trophic level, so after four or five links too little is left to support another level.
Raymond Lindeman's ten percent law says that only about 10 percent of the energy at one level is passed on to the next; the rest is used up in respiration, movement and body heat, or lost in undigested and dead matter. If plants fix 10,000 units of energy, herbivores get about 1,000, primary carnivores about 100 and secondary carnivores only about 10. This is why energy flow is one-way, why the pyramid of energy is always upright, and why top predators such as tigers are few in number.
A is wrong: it is the reverse; lower levels hold more energy than higher ones.
C is wrong: control of lower levels by higher ones does not decide how long a food chain is.
D is wrong: parasites have nothing to do with the limit on trophic levels.
Exam tip: 10 percent law (Lindeman, 1942); the pyramid of energy is never inverted.
Practice Questions
View allConsider the following :
1. Battery storage
2. Biomass generators
3. Fuel cells
4. Rooftop solar photovoltaic units
How many of the above are considered "Distributed Energy Resources"?
- A.Only one
- B.Only two
- C.Only three
- D.All four
Show answer
Battery storage, biomass generators, fuel cells and rooftop solar units are all small, local sources that generate or store power close to where it is used, which is what Distributed Energy Resources are.
Read the full explanation →Due to some reasons, if there is a huge fall in the population of species of butterflies, what could be its likely consequence/consequences ?
1. Pollination of some plants could be adversely affected.
2. There could be a drastic increase in the fungal infections of some cultivated plants.
3. It could lead to a fall in the population of some species of wasps, spiders and birds.
Select the correct answer using the code given below :
- A.1 only
- B.2 and 3 only
- C.1 and 3 only
- D.1, 2 and 3
Show answer
Butterflies are pollinators and also food for many animals, so their decline would hurt pollination and their predators; it has no direct link with fungal diseases of crops.
Read the full explanation →Consider the following statements :
1. Lions do not have a particular breeding season.
2. Unlike most other big cats, cheetahs do not roar.
3. Unlike male lions, male leopards do not proclaim their territory by scent marking.
Which of the statements given above are correct ?
- A.1 and 2 only
- B.2 and 3 only
- C.1 and 3 only
- D.1, 2 and 3
Show answer
Lions breed at any time of year and cheetahs cannot roar, but male leopards do mark their territory with scent.
Read the full explanation →Which one of the following National Parks lies completely in the temperate alpine zone?
- A.Manas National Park
- B.Namdapha National Park
- C.Neora Valley National Park
- D.Valley of Flowers National Park
Show answer
Set high in the Garhwal Himalaya of Uttarakhand, roughly between 3,200 and 6,600 metres, it lies wholly in the temperate alpine zone.
Read the full explanation →Consider the following kinds of organisms:
1. Copepods
2. Cyanobacteria
3. Diatoms
4. Foraminifera
Which of the above are primary producers in the food chains of oceans?
- A.1 and 2
- B.2 and 3
- C.3 and 4
- D.1 and 4
Show answer
Cyanobacteria and diatoms carry out photosynthesis, so they are phytoplankton, the primary producers at the base of ocean food chains.
Read the full explanation →