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🔬 Biology  ·  Organisms and Populations  ·  NEET

Which chemical defence is produced by plants such as tobacco and Cinchona to deter herbivores?

Answer: Nicotine and quinine.

  • A Chlorophyll and starch
  • B Nicotine and quinine
  • C Cellulose and lignin
  • D Glucose and sucrose

Correct answer: B. Nicotine and quinine

Explanation: Plants produce defensive chemicals like nicotine, quinine, strychnine and caffeine that deter or poison grazing herbivores.

Exponential (J-curve) vs Logistic (S-curve) GrowthtimePopulation (N)Exponential (unlimited resources)K (carrying capacity)Logistic (limited resources)Logistic growth slows as N approaches K; exponential growth never slows down

Exponential growth produces an ever-steepening J-curve with no limit, an unrealistic long-term model; logistic growth produces an S-curve that levels off at the carrying capacity K, as growth rate (K−N)/K shrinks to zero once resources are fully used.

Concept context

How organisms interact with abiotic factors and respond to stress, plus population attributes, growth models, and interspecific interactions such as predation, competition, and mutualism.

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