NEET 2021 question paper with solutions

1. Understand the phenomenon being described: some plants can modify their form, developing different kinds of structures, in order to adapt and cope with changes in their surrounding environment. Given this,

is called plasticity.

2. Recognize the two types of plasticity: this can be intrinsic plasticity (arising from within the plant, such as differences between juvenile and mature leaves) or extrinsic plasticity (a response to outside environmental factors). In both cases, the plant may show heterophylly, seen for example in the leaves of larkspur and buttercup.

3. Eliminate the other options: maturity refers to the final specialised state a structure reaches; elasticity and flexibility are physical/mechanical terms unrelated to this biological developmental concept.

Hence, the correct answer is D. Plasticity.

1. Recall the causative agent of Filariasis (elephantiasis) — it is caused by the filarial worm Wuchereria bancrofti, which affects the lymphatic vessels of the lower limbs, so (a) → (iii).

2. Recall the causative agent of Amoebiasis — it is caused by the protozoan parasite Entamoeba histolytica, which infects the large intestine, so (b) → (iv).

3. Recall a causative agent of Pneumonia — it can be caused by bacteria such as Haemophilus influenzae, so (c) → (i).

4. Recall the causative agent of Ringworm — it is caused by fungi such as Trichophyton (along with Microsporum and Epidermophyton), so (d) → (ii).

5. Hence, the correct matching is (a)-(iii), (b)-(iv), (c)-(i), (d)-(ii) (Option C).

1. Recall Chargaff's rule for double-stranded DNA.

Given that adenine always pairs with thymine and guanine always pairs with cytosine, their percentages must match:

2. Apply this rule using the given percentage of Adenine.

Given that $\%A = 30\%$, we get:

3. Find the remaining percentage for G and C together.

Since the total of all four bases must equal 100%:

Given that $\%G = \%C$, each must be:

Conclusion: Hence, T = 30%, G = 20%, C = 20%, so the answer is D.