Zoology MCQs for NEET — Practice Questions with Answers

Genetic variation refers to differences in DNA among individuals. Eye color is determined by genetic differences, making it a clear example of genetic variation. In contrast, age, scars, or diet preferences are not determined by genetic factors.

Environmental variation refers to differences caused by environmental factors rather than genetic inheritance. In this case, Marge dyeing her hair blue is an example of environmental variation because it is influenced by her personal choice and environmental factors, not by her genes.

Genetic drift is a mechanism of evolution that involves random changes in the frequency of alleles in a population. It does not involve competition between members of a species, unlike natural selection which is driven by differential survival and reproduction based on advantageous traits.

George Cuvier, a French naturalist and paleontologist, attributed extinctions in nature to catastrophic events. He believed that sudden, short-lived, violent events, such as natural disasters, were responsible for mass extinctions of species.

Darwin delayed publishing 'The Origin of Species' because he was concerned about the potential negative reaction from the scientific community and the public regarding the implications of his theory. He knew that his ideas challenged the prevailing views of creation and feared the controversy it would generate. This hesitation was compounded by the fact that he was a meticulous scientist who wanted to gather as much evidence as possible to support his theory.

Reproductive isolation is crucial from an evolutionary standpoint because it prevents the exchange of genetic material between two populations of the same species. This interruption in gene flow allows the populations to diverge genetically over time, potentially leading to speciation. Speciation is the formation of new and distinct species in the course of evolution, which is a fundamental process driving biodiversity.

Although the mutations themselves are random, natural selection is a non-random process. Natural selection acts on variations that enhance survival and reproduction, making it a directed process. This means that while the origin of variations (mutations) is random, the process by which certain traits become more common in a population over time is predictable based on environmental pressures and the advantages they confer.

During the evolutionary synthesis in the 1930s and 1940s, scientists reconciled Mendel's work with Darwin's theory by recognizing that thinking about species as populations rather than individuals removes any incompatibility. Additionally, it was acknowledged that much of the genetic variation observed in nature is due to recombination (the reshuffling of genes during sexual reproduction) rather than mutation alone. This synthesis integrated Mendelian genetics with natural selection, forming a comprehensive framework for evolutionary biology.

Darwin's theory of common descent is supported by multiple lines of evidence: patterns in the fossil record indicating divergence from a common ancestor, biogeographic patterns showing related species in specific regions, and common embryological stages among different vertebrates. These evidences collectively point towards the idea that diverse species have evolved from common ancestors over time.