Free swimming macroscopic animals in an aquatic environment are referred to as
- A.Plankton
- B.Periphyton
- C.Benthos
- D.Nekton
Correct answer
Explanation
The correct answer is D, Nekton. Nekton are animals large enough to be seen with the naked eye that swim actively and can move against water currents.
Ecologists group aquatic organisms by where and how they live. Fish, whales, dolphins, turtles, squid and seals are nekton, because their own swimming decides where they go. The word comes from a Greek word meaning swimming. Nekton live mostly in open water and include many top predators of aquatic food chains.
A is wrong because plankton are mostly tiny organisms, such as algae and copepods, that drift with the currents and cannot swim against them. B is wrong because periphyton is the mix of algae, bacteria and other microbes that grows attached to submerged surfaces like rocks and plant stems. C is wrong because benthos are organisms that live on or in the bottom of a water body, such as crabs, worms, starfish and clams.
Exam tip: plankton drift, nekton swim, benthos live on the bottom, neuston live at the surface film.
Practice Questions
View allWhich of the following is/are renewable source(s) of energy? 1. Fossil fuel 2. Biofuel 3. Uranium 4. Hydropower Select the correct answer using the code given below.
- A.2 only
- B.3 and 4
- C.1 and 3
- D.2 and 4
Show answer
Biofuel and hydropower are renewable because nature replaces them within a human lifetime, while fossil fuels and uranium are not.
Read the full explanation →Which one of the following is NOT decomposed by bacterial action ?
- A.Vegetable remains
- B.Plastic materials
- C.Animal carcasses
- D.Wastes of flowers
Show answer
Ordinary plastics are non-biodegradable, so bacteria and fungi cannot break them down in any useful length of time. Most plastics, such as polyethylene, polypropylene and PVC, are long synthetic polymers made from petroleum.
Read the full explanation →According to the Environmental Protection Agency (EPA), which one of the following is the largest source of sulphur dioxide emissions?
- A.Locomotives using fossil fuels
- B.Ships using fossil fuels
- C.Extraction of metals from ores
- D.Power plants using fossil fuels
Show answer
The EPA names the burning of fossil fuels by power plants and other industrial facilities as the largest source of sulphur dioxide.
Read the full explanation →Artificial way of causing rainfall to reduce air pollution makes use of
- A.silver iodide and potassium iodide
- B.silver nitrate and potassium iodide
- C.silver iodide and potassium nitrate
- D.silver nitrate and potassium chloride
Show answer
These salts are the usual seeding agents in cloud seeding, the artificial way to make rain. Cloud seeding sprays tiny particles into clouds that already hold moisture, from aircraft, rockets or ground generators.
Read the full explanation →As per the Solid Waste Management Rules, 2016 in India, which one of the following statements is correct?
- A.Waste generator has to segregate waste into five categories.
- B.The Rules are applicable to notified urban local bodies, notified towns and all industrial townships only.
- C.The Rules provide for exact and elaborate criteria for the identification of sites for landfills and waste processing facilities.
- D.It is mandatory on the part of waste generator that the waste generated in one district cannot be moved to another district.
Show answer
The 2016 Rules set out detailed criteria for choosing sites for landfills and waste processing facilities. The Solid Waste Management Rules, 2016, framed under the Environment (Protection) Act, 1986, replaced the Municipal Solid Wastes Rules of 2000.
Read the full explanation →