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1. Introduction to Ecology

• Ecology: Study of interactions between organisms and their environment.
• Levels of ecological organization:
  • Organism → Individual living being
  • Population → Group of same species in an area
  • Community → Group of populations
  • Ecosystem → Community + abiotic environment

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2. Organisms and Adaptations

• Organism: Individual living unit.
• Adaptations help survival in habitat:
  • Structural → Physical features (thick fur in polar bear)
  • Physiological → Internal functions (salt excretion in marine animals)
  • Behavioural → Actions (migration of birds)

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3. Population Ecology

• Population: Group of individuals of same species in a particular area.
• Population characteristics:
  1. Population density – Number of individuals per unit area.
  2. Population growth – Increase in population size over time.
     • Exponential growth (J-shaped curve) – Unlimited resources
     • Logistic growth (S-shaped curve) – Limited by carrying capacity (K)
  3. Natality – Birth rate
  4. Mortality – Death rate
  5. Age structure – Distribution of individuals in age classes
  6. Dispersion – Distribution of individuals
     • Clumped, uniform, random

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4. Population Interactions

• Intraspecific competition → Between members of same species
• Interspecific competition → Between members of different species
• Predation → One organism eats another
• Parasitism → One benefits, other is harmed
• Mutualism → Both benefit
• Commensalism → One benefits, other unaffected

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5. Population Growth Models

1. Exponential Model:
   • $\frac{dN}{dt} = rN$dtdN​=rN
   • Rapid growth without limiting factors
2. Logistic Model:
   • $\frac{dN}{dt} = rN \left(1 – \frac{N}{K}\right)$dtdN​=rN(1−KN​)
   • Growth slows near carrying capacity (K)

Ecology: Organisms and Populations | MCQs

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1. Organisms and Adaptations

1. The study of interactions between organisms and their environment is called:
   a) Anatomy
   b) Physiology
   c) Ecology
   d) Evolution
   Answer: c) Ecology
2. Thick fur in polar bears is an example of:
   a) Behavioural adaptation
   b) Structural adaptation
   c) Physiological adaptation
   d) Random variation
   Answer: b) Structural adaptation
3. Salt excretion in marine animals is an example of:
   a) Structural adaptation
   b) Physiological adaptation
   c) Behavioural adaptation
   d) Population growth
   Answer: b) Physiological adaptation
4. Migration of birds to avoid winter is an example of:
   a) Behavioural adaptation
   b) Structural adaptation
   c) Physiological adaptation
   d) Genetic drift
   Answer: a) Behavioural adaptation

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2. Population Characteristics

5. Population density is defined as:
   a) Number of species in an area
   b) Number of individuals per unit area
   c) Age distribution of population
   d) Birth rate
   Answer: b) Number of individuals per unit area
6. Birth rate in population ecology is called:
   a) Natality
   b) Mortality
   c) Dispersion
   d) Growth rate
   Answer: a) Natality
7. Death rate in population ecology is called:
   a) Natality
   b) Mortality
   c) Dispersion
   d) Carrying capacity
   Answer: b) Mortality
8. Clumped, uniform, and random are types of:
   a) Population growth
   b) Dispersion
   c) Adaptation
   d) Community
   Answer: b) Dispersion

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3. Population Growth

9. Exponential population growth shows which type of curve?
   a) S-shaped
   b) J-shaped
   c) Linear
   d) Bell-shaped
   Answer: b) J-shaped
10. Logistic population growth slows near:
    a) Birth rate
    b) Death rate
    c) Carrying capacity (K)
    d) Growth rate (r)
    Answer: c) Carrying capacity (K)
11. The formula for logistic growth is:
    a) $\frac{dN}{dt} = rN$dtdN​=rN
    b) $\frac{dN}{dt} = rN \left(1 – \frac{N}{K}\right)$dtdN​=rN(1−KN​)
    c) $N = P + Q$N=P+Q
    d) $r = K – N$r=K−N
    Answer: b) $\frac{dN}{dt} = rN \left(1 – \frac{N}{K}\right)$dtdN​=rN(1−KN​)

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4. Population Interactions

12. Competition between individuals of the same species is called:
    a) Intraspecific competition
    b) Interspecific competition
    c) Predation
    d) Mutualism
    Answer: a) Intraspecific competition
13. One organism benefits while the other is harmed is called:
    a) Mutualism
    b) Commensalism
    c) Parasitism
    d) Predation
    Answer: c) Parasitism
14. Both organisms benefit in a relationship called:
    a) Commensalism
    b) Mutualism
    c) Parasitism
    d) Competition
    Answer: b) Mutualism
15. One organism benefits while the other is unaffected is called:
    a) Mutualism
    b) Parasitism
    c) Commensalism
    d) Predation
    Answer: c) Commensalism
16. A lion hunting a deer is an example of:
    a) Mutualism
    b) Parasitism
    c) Predation
    d) Competition
    Answer: c) Predation