Man and his Environment MCQs for MDCAT Practice

Biology section, Man and his Environment chapter. Up to eight free sample questions, each with the correct answer and a worked explanation. The full chapter opens in the app.

1. Question 1
   What is the reason for the highest biomass being present in the aquatic ecosystem?
   • ANano plankton, blue-green algae, and green algae
   • BSea grass and slime molds
   • CBenthic and brown algae (correct answer)
   • DDiatoms
   Correct answer: C

   Aquatic ecosystems boast the highest biomass due to the photosynthetic efficiency and widespread distribution of benthic and brown algae, forming the base of the food web.
2. Question 2
   The six critical elements of life are hydrogen, carbon, nitrogen, oxygen and:
   • ACalcium and phosphorus
   • BSodium and phosphorus
   • CPotassium and phosphorus
   • DSulfur and phosphorus (correct answer)
   Correct answer: D

   Identify the two additional essential elements, alongside C, H, N, and O, that constitute the bulk of organic matter in living organisms.
3. Question 3
   Ultraviolet radiations from sunlight causes a reaction that produces:
   • AFluorides
   • BCarbon monoxide
   • CSulphur dioxide
   • DOzone (correct answer)
   Correct answer: D

   Sunlight's UV rays trigger a reaction forming ozone ($O_3$) in the stratosphere, essential for absorbing harmful UV radiation.
4. Question 4
   Giraffes and koalas live in the same forest and feed on grass. What is the ecological interaction between giraffe and koala?
   • APredation
   • BParasitism
   • CCompetition (correct answer)
   • DCommensalism
   Correct answer: C

   When two species share limited resources, like food, they engage in competition for survival.
5. Question 5
   Which one of the following pairs is not correctly matched?
   • AStreptomyces- Antibiotic
   • BSerratia-Drug addiction (correct answer)
   • CSpirulina Single-celll protein
   • DRhizobium­-Biofertilizer
   Correct answer: B

   This question tests your knowledge of symbiotic relationships and beneficial microorganisms, differentiating their roles as antibiotic producers, drug additives, single-cell protein sources, or biofertilizers.
6. Question 6
   In an area where DDT had been used extensively, the population of birds declined significantly because:
   • ABirds stopped laying eggs.
   • BEarthworms in the area got eradicated.
   • CCobras were feeding exclusively on birds.
   • DMany of the birds eggs laid, did not hatch. (correct answer)
   Correct answer: D

   DDT's biomagnification in birds leads to eggshell thinning and reproductive failure, causing population decline.
7. Question 7
   Select the correct food chain:
   • AGrass -- Chameleon -- Insect -- Bird
   • BGrass -- Fox -- Rabbit -- Bird
   • CPhytoplankton -- Zooplankton -- Fish (correct answer)
   • DFallen leaves -- Bacteria -- Insect larvae
   Correct answer: C

   This question tests understanding of trophic levels and the correct flow of energy in a food chain, emphasizing producers, primary consumers, and secondary consumers.
8. Question 8
   Which of the following describes an ecological niche?
   • AThe physical location where an organism finds its food supply
   • BThe habitat providing the most favorable climate for an organism
   • CThe interactions between an organism and other species within its ecosystem
   • DThe comprehensive role and strategies of an organism in utilizing its environment (correct answer)
   Correct answer: D

   An ecological niche is the complete role and resource use of a species within its environment, encompassing all interactions and adaptations.

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