3 past-year Organisms and Populations questions from NEET (Biology).
Q139 (2024)
Which one of the following is an appropriate example of sexual deceit?
- Female wasp and fig
- Cuckoo and crow
- Ophrys and bumblebee
- Sea anemone and clown fish
### Related Formula
$\text{Sexual Deceit} \rightarrow \text{Mediterranean Orchid } (Ophrys) + \text{Male Bumblebee}$
### Core Logic
The Mediterranean orchid *Ophrys* employs sexual deceit to get pollinated. One petal of its flower bears an uncanny resemblance to the female bee in size, colour, and markings. The male bumblebee pseudocopulates with the flower and in the process gets dusted with pollen, thereby aiding in pollination.
### Step 1: Categorization of Interaction Examples
* Female wasp and fig: Mutualism
* Cuckoo and crow: Brood parasitism
* Ophrys and bumblebee: Sexual deceit (Pseudocopulation)
* Sea anemone and clown fish: Commensalism
### Pattern Recognition
Sees: "sexual deceit".
Shortcut: *Ophrys* orchid and bumblebee pollination interaction.
### Evaluation Rubric / Model Answer
null
### Chapter Mix
Class 12 Biology: Organisms and Populations
Q165 (2024)
Which of the following equations depicts Verhulst-Pearl logistic population growth?
- $\frac{dN}{dt} = rN\left(\frac{K - N}{K}\right)$
- $\frac{dN}{dt} = rN\left(\frac{K + N}{K}\right)$
- $\frac{dN}{dt} = rN\left(\frac{K}{K - N}\right)$
- $\frac{dN}{dt} = rN\left(\frac{K - N}{N}\right)$
### Related Formula
$$\frac{dN}{dt} = rN \left( \frac{K - N}{K} \right)$$
where $N = \text{population density at time } t$, $r = \text{intrinsic rate of natural increase}$, $K = \text{carrying capacity}$.
### Core Logic
Verhulst-Pearl logistic growth models population growth in a resource-limited environment. The differential equation is given by $\frac{dN}{dt} = rN \left( \frac{K - N}{K} \right)$, where $\frac{K - N}{K}$ represents environmental resistance.
### Step 1: Conclusion
Option (1) correctly represents the logistic growth equation.
### Pattern Recognition
Sees: "Verhulst-Pearl logistic growth equation".
Shortcut: $\frac{dN}{dt} = rN\left(\frac{K - N}{K}\right)$.
### Evaluation Rubric / Model Answer
null
### Chapter Mix
Class 12 Biology: Organisms and Populations
Q180 (2024)
Choose the correct statements regarding population interactions between two species.
A. In both parasitism and commensalism, only one species benefits and the other species is harmed.
B. Both species benefit in mutualism.
C. Both species benefit in commensalism.
D. In parasitism, only one species benefits and the other species is harmed.
E. In amensalism, one species is harmed and the other is unaffected.
Choose the correct answer from the options given below:
- A and D only
- A and B only
- B and E only
- B, D and E only
### Related Formula
$\begin{aligned}
\text{Mutualism} &\rightarrow (+, +)\\
\text{Parasitism} &\rightarrow (+, -)\\
\text{Commensalism} &\rightarrow (+, 0)\\
\text{Amensalism} &\rightarrow (-, 0)
\end{aligned}$
### Core Logic
Evaluating statements on species interactions:
* A (Incorrect): In commensalism, one species benefits and the other is unaffected (not harmed).
* B (Correct): In mutualism, both species benefit (+, +).
* C (Incorrect): In commensalism, only one species benefits (+, 0).
* D (Correct): In parasitism, parasite benefits and host is harmed (+, -).
* E (Correct): In amensalism, one species is harmed and the other is unaffected (-, 0).
### Step 1: Visual Interaction Table
{{SOL_IMG1}}
Statements B, D, and E are correct.
### Pattern Recognition
Sees: "Mutualism (+,+), Parasitism (+,-), Amensalism (-,0)".
Shortcut: Correct statements are B, D, and E.
### Evaluation Rubric / Model Answer
null
### Chapter Mix
Class 12 Biology: Organisms and Populations
