AIPMT 2005 question paper with solutions

192 questions · 180 min

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Sample questions with solutions

The ability of the Venus Flytrap to capture insects is due to

A.
specialized ''muscle-like'' cells
B.
chemical stimulation by the prey
C.
a passive process requiring no special ability on the part of the plant
D.
rapid turgor pressure changes.

Answer: D

Recall the type of movement shown by Venus Flytrap: this plant shows a thigmonastic movement, a non-directional response to touch, which is also seen in other insectivorous plants like Dionaea and Drosera, and is triggered by sensitive tentacle-like trigger hairs.
Understand the mechanism behind the trap closing: when the trigger hairs are touched, an action potential is generated, causing hydrogen ions to be rapidly pumped into the walls of cells on the outside of each leaf. Given this,

\text{Touch stimulus} \rightarrow \text{Action potential} \rightarrow \text{Rapid H}^+ \text{ pumping into outer cell walls}

Trace the consequence of this ion pumping: the protons loosen the cell walls so rapidly that the tissue becomes flaccid, allowing the cells to quickly absorb water, causing the outer side of each leaf to expand. Therefore,

\text{Rapid turgor pressure change} \rightarrow \text{Trap snaps shut}

Eliminate the other options: plants do not have true muscle cells (option A); mere chemical stimulation by prey (option B) is not the direct mechanical cause of closing; and this is clearly not a passive process (option C), since it involves an active, rapid physiological response.

Hence, the correct answer is D. rapid turgor pressure changes.

At a particular locus, frequency of 'A' allele is 0.6 and that of 'a' is 0.4. What would be the frequency of heterozygotes in a random mating population at equilibrium ?

A.
0.48
B.
0.24
C.
0.36
D.
0.16

Answer: A

Recall the Hardy-Weinberg equation for a gene with two alleles $A$ (frequency $p$ ) and $a$ (frequency $q$ ):

p^2 + 2pq + q^2 = 1

Here, $2pq$ specifically represents the frequency of heterozygous individuals ( $Aa$ ), since one allele comes from $A$ (probability $p$ ) and the other from $a$ (probability $q$ ), and this can happen in two ways.

Given that $p = 0.6$ (frequency of allele $A$ ) and $q = 0.4$ (frequency of allele $a$ ), substitute these values into the heterozygote frequency formula.

2pq = 2 \times 0.6 \times 0.4

Calculating this:

2pq = 0.48

Hence, the frequency of heterozygotes in this population is 0.48, so the answer is A.

In a type of apomixis known as advice embryony, embryos develop directly from the

A.
nucellus or integuments
B.
zygote
C.
synergids or antipodals in an embryo sac
D.
accessory embryo sacs in the ovule.

Answer: A

Apomixis is a type of asexual reproduction in flowering plants where embryos form without fertilization.
One specific type of apomixis, called adventive embryony, involves embryos developing directly from the diploid sporophytic tissues surrounding the embryo sac — specifically the nucellus or integuments — rather than from any gametic cell.
This is seen in examples like Citrus and mango.
Hence, the answer is Option A: nucellus or integuments.

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