CUET UG Biology Booster Test 2 Theories and Mechanisms of Evolution

The Theory of Special Creation posits three main pillars: all organisms were created as they are now, the diversity has remained unchanged (static), and Earth is relatively young (4,000 years). The concept of extinction and the appearance of new forms over geological time (geological succession/evolution) is a direct contradiction to the "unchanging" premise of the Theory of Special Creation.

The correct matches are: Elongation of a giraffe's neck (1) → Use and Disuse (C) because Lamarck proposed that repeated stretching of the neck led to its elongation over generations. Origin of distinct finch beaks (2) → Adaptive Radiation (A) because a common ancestral finch diversified into multiple species adapted to different ecological niches. Melanised moths surviving in polluted areas (3) → Natural Selection (B) because darker moths gained a survival advantage in polluted environments and became more common. Therefore, the correct matching is: 1-C, 2-A, 3-B Answer: B

Darwin's logic flowed from his global voyage (3), during which he observed similarities between existing and extinct life forms (1). This led to the recognition of gradual evolutionary change (4), eventually culminating in his mechanistic conclusion that better-adapted individuals will outbreed others (2).

Darwin's observations highlighted that life forms change over time, meaning many ancient forms have gone extinct (I). He also noted that extinctions and the emergence of new forms occurred throughout Earth's history (II). Statement III is false because geological history is directly correlated with biological history through the fossil record.

Darwinian evolution explains this through Natural Selection. Population B possesses a "built-in" variation that confers higher fitness in the new medium. Because they are better fit, they reproduce more successfully than population A, leading to their dominance and the divergence of their lineage.

Organisms do not "choose" or "immediately mutate" to acquire traits because the environment requires them to. Mutations are random events that occur independently of the environmental need. Populations that are less endowed simply suffer reduced survival and reproductive success (Options A, B, and D), not active, directed adaptation.

The logical order is: First, a colony with inherent variation exists (2). Then, the environmental medium changes (4). This triggers the environment to "select" those individuals whose variations provide higher fitness (3). Finally, those individuals reproduce, outgrow the others, and the population shifts to the variant type (1).

The convergence of Darwin and Wallace on the same theory suggests that Natural Selection was not a subjective idea, but an objective, observable, and verifiable physical process occurring in nature. It validates the theory because it was independently observed across different parts of the world.

Statement I is correct; natural populations are generally stable in size. Statement II is correct; variation is universal among individuals. Statement III is false because resources are limited, which is precisely why exponential growth does not occur in nature, despite the theoretical potential.

Exponential growth occurs when individuals reproduce at their maximum rate without environmental resistance. A bacterial population in a nutrient-rich, unrestrictive medium provides the closest approximation to this theoretical state, whereas predators and giraffes are inherently limited by their ecosystem's carrying capacity.

In Darwinian evolution: Adaptive ability (1) → Inherited (B) because adaptive traits are passed from parents to offspring. Fitness (2) → End result of adaptation (A) because fitness measures reproductive success achieved through adaptation. Variation (3) → Heritable and resource-optimizing (C) because only heritable variations contribute to evolutionary change. Progeny (4) → Increased in survivors (D) because organisms with advantageous traits produce more surviving offspring. Therefore, the correct matching is: 1-B, 2-A, 3-C, 4-D

Built-in variation means that within any population, there are individuals with different genetic traits. When an environment changes, this pre-existing diversity is crucial because some individuals may already possess traits that allow them to survive the new conditions, thus preventing the extinction of the species.

De Vries explicitly rejected the Darwinian view of gradual evolution. His Mutation Theory proposed that evolution occurs via sudden, large "jumps" (saltations), which are often random rather than directional. Hence, calling his process "gradual and directional" is the opposite of his theory.

In his work on Oenothera lamarckiana, Hugo de Vries observed that new phenotypes appeared abruptly. He termed these large, sudden heritable differences "mutations" and argued they were the true source of new species, rather than the minor, slow accumulations Darwin described.

Evolution is not a directed or deterministic process. Because mutations occur randomly and environmental changes are unpredictable, evolution is a stochastic (probabilistic) process. The selection of a trait depends on the interaction of these random variables.

Alfred Russel Wallace co-proposed the theory of Natural Selection alongside Darwin. The concept of "Random, directionless mutation" belongs to Hugo de Vries, not Wallace. Thus, this association is false.

The passage emphasizes that fitness relies on traits that are "inherited," which necessitates a "genetic basis." This genetic basis is what allows a beneficial adaptive ability to be passed on to future generations, thereby translating individual adaptation into evolutionary fitness.

The passage explicitly concludes by identifying the two pillars of Darwinian theory: Branching Descent (describing how species diverge) and Natural Selection (describing the mechanism of survival).

The conflict between Darwinian gradualism and De Vriesian mutationism was resolved through the "Modern Synthesis" of the 1930s and 40s, which was built on studies in population genetics. It explained that mutations provide the variation, and natural selection acts on those variations in a gradual way, combining both perspectives.

Evolution is fundamentally about the propagation of genes over generations. Because microbes have very short life cycles (generation times), they can undergo many cycles of mutation and natural selection in a short time. Fowls and fishes have long life cycles, meaning their evolutionary change across generations takes much longer in absolute time.