Q.Read the following passage and answer the questions that follow. According to evolutionary theory, every evolutionary change involves the substitution of a new gene for the old one and the new allele arises from the old one. Continuous accumulation of changes in the DNA coding for proteins leads to evolutionary differences. The chemical composition of DNA is basically the same in all living beings, except for differences in the sequence of nitrogenous bases. Given below are percentage relative similarities between human DNA and DNA of other vertebrates : [Table — S.No. | Vertebrates | Percentage similarities: 1. Chimpanzee 100; 2. Gibbon 94; 3. Rhesus Monkey 88; 4. Lemur 47; 5. Treeshrew 28; 6. Mouse 21; 7. Hedgehog 19; 8. Chicken 10]

When organic matter — dead leaves, animal waste, plant litter — falls to the ground, it doesn't simply vanish. It is broken down through decomposition, a process driven by two groups of organisms working in concert: detritivores (earthworms, millipedes, woodlice) that physically fragment the material, and decomposers (bacteria and fungi) that chemically break down complex molecules into simpler nutrients the soil can absorb.

The speed of decomposition hinges on several factors. Temperature and moisture create the physical environment — warmth accelerates microbial activity, moisture keeps organisms hydrated and mobile. But given that all three soil samples in this question share identical temperature and moisture conditions, the deciding factor becomes the population of organisms doing the actual work — the contents 1-4 plotted in the source graph.

Concept and Intuition

Weeds are often defined as "plants out of place," but from an ecological perspective, they are typically pioneer species or ruderals. These are plants that are excellent at colonizing disturbed or open habitats. Abandoned fields represent a classic example of such a disturbed habitat.

When a field is abandoned, the regular human interventions like tilling, weeding, irrigation, and fertilization cease. This creates an environment where:

1. Competition changes: The dominant cultivated crops are no longer present, and the field is open for other plants to colonize.
2. Environmental conditions can be harsh: The soil might be depleted of nutrients, exposed to intense sunlight, and prone to drought, as there's no active management to maintain optimal growing conditions.
3. Herbivory pressure might increase: Without human protection, plants are more exposed to grazing animals.

Calotropis (commonly known as Aak or Madar) possesses specific biological traits that make it exceptionally well-suited to exploit these conditions, allowing it to thrive where many other plants would struggle.

Reasons for Flourishing

1. Reduced Competition and Absence of Agricultural Practices:

   In an abandoned field, the primary competitors—the cultivated crops—are no longer present. Farmers also cease practices like tilling, weeding, and herbicide application, which actively suppress weed growth. This creates an open niche with abundant resources (sunlight, space, water, and available nutrients) that Calotropis can readily exploit. As a fast-growing, opportunistic species, it can quickly establish itself and outcompete other early colonizers that might be less robust or slower growing. The lack of disturbance allows its root system to develop undisturbed and its aerial parts to grow without being cut back.

2. Tolerance to Harsh Environmental Conditions and Effective Anti-Herbivory Mechanisms: …