Population & Community Ecology

Level 1: Recognition Test

Time Limit: 20 minutes Total Marks: 30

---

Section A — Multiple Choice (1 mark each)

Choose the single best answer.

Q1. Population density is best defined as: a) The total number of individuals in a species b) The number of individuals per unit area or volume c) The spatial pattern of individuals in a habitat d) The rate of population increase over time

Q2. Exponential growth of a population is represented by which shape of curve? a) S-shaped (sigmoid) b) J-shaped c) Flat horizontal line d) Bell-shaped

Q3. The maximum population size an environment can sustain indefinitely is called: a) Biotic potential b) Population density c) Carrying capacity ($K$) d) Environmental resistance

Q4. Which of the following is a density-dependent factor? a) A hurricane b) A sudden frost c) Competition for food d) A volcanic eruption

Q5. A Type III survivorship curve is characterised by: a) High survival in early life, high mortality late in life b) Constant mortality rate throughout life c) Very high mortality in early life, few survivors reaching old age d) No mortality until the maximum lifespan

Q6. Which describes a K-selected species? a) Many offspring, little parental care, short lifespan b) Few offspring, much parental care, long lifespan c) Rapid population growth with no stable size d) Colonises disturbed habitats first

Q7. In the relationship where one organism benefits and the other is unaffected, we have: a) Mutualism b) Parasitism c) Commensalism d) Competition

Q8. A keystone species is one that: a) Is always the most abundant in a community b) Has a disproportionately large effect on community structure relative to its abundance c) Is the largest organism in the ecosystem d) Only exists in aquatic ecosystems

Q9. The logistic growth equation is: a) $\dfrac{dN}{dt} = rN$ b) $\dfrac{dN}{dt} = rN\left(\dfrac{K-N}{K}\right)$ c) $\dfrac{dN}{dt} = K - N$ d) $\dfrac{dN}{dt} = rNK$

Q10. Biodiversity is important primarily because it: a) Guarantees exponential growth of all species b) Increases ecosystem stability and resilience c) Eliminates all competition d) Prevents any predation

---

Section B — Matching (1 mark each, 6 marks)

Q11. Match each interaction (Column A) with its correct outcome (Column B).

Column A	Column B
(i) Mutualism	(P) +/− (one benefits, one harmed)
(ii) Parasitism	(Q) −/− (both harmed)
(iii) Interspecific competition	(R) +/+ (both benefit)
(iv) Commensalism	(S) +/0 (one benefits, one unaffected)
(v) Predation	(T) +/− (predator gains, prey killed)
(vi) Intraspecific competition	(U) −/− (within same species)

---

Section C — True/False with Justification (2 marks each: 1 for T/F, 1 for justification)

Q12. Exponential growth can continue indefinitely in a natural environment.

Q13. Density-independent factors affect the same proportion of a population regardless of its size.

Q14. In predator–prey cycles, a rise in the prey population is typically followed by a rise in the predator population.

Q15. A random distribution pattern occurs when individuals strongly attract or repel one another.

Q16. Removing a keystone species may cause the collapse of many other populations in the community.

Q17. r-selected species usually show a Type I survivorship curve.

---

[
  {"claim":"Logistic growth rate is zero when N equals K",
   "code":"r,N,K=symbols('r N K',positive=True); dNdt=r*N*(K-N)/K; result=(dNdt.subs(N,K)==0)"},
  {"claim":"At small N logistic rate approaches exponential rate rN",
   "code":"r,N,K=symbols('r N K',positive=True); dNdt=r*N*(K-N)/K; result=(limit(dNdt/(r*N),N,0)==1)"},
  {"claim":"Total marks sum to 30 (10 MCQ + 6 matching + 14 TF)",
   "code":"result=(10+6+14==30)"},
  {"claim":"Section C has 6 questions worth 2 marks each equals 14... check 6*2=12 not 14 so TF total is 12",
   "code":"result=(6*2==12)"}
]